Texas Lizards: A Field Guide 9780292771963

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TEXAS LIZARDS

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T E X A S N AT U R A L H I S T O RY G U I D E S™

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TEXAS LIZARDS A F I E LD G U I D E

T R OY D. H I B B I T T S A N D T O BY J . H I B B I T T S

Foreword by Laurie J. Vitt

UNIV ERSIT Y OF TE X AS PRESS

Austin

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Copyright © 2015 by the University of Texas Press All rights reserved Printed in China First edition, 2015 Unless otherwise indicated, all photographs were taken by the authors. Requests for permission to reproduce material from this work should be sent to: Permissions University of Texas Press P.O. Box 7819 Austin, TX 78713-7819 http://utpress.utexas.edu/index.php/rp-form The paper used in this book meets the minimum requirements of ANSI/ NISO Z39.48-1992 (R1997) (Permanence of Paper). Library of Congress Cataloging-in-Publication Data Hibbitts, Troy D., 1970– Texas lizards : a field guide / Troy D. Hibbitts and Toby J. Hibbitts. — First edition. pages cm. — (Texas natural history guides) Includes bibliographical references and index. ISBN 978-0-292-75934-3 (pbk. : alk. paper) 1. Lizards—Texas—Identification. I. Hibbitts, Toby J. II. Title. QL653.T4H48 2015 597.9509764—dc23 2014015276 doi:10.7560/759343

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We dedicate this book to our father, Terry Hibbitts, who passed on his passion for the natural world, and for reptiles and amphibians in particular, to his two sons through countless hours spent together in the field. We dedicate it also to the Texas Herpetological Society for its role in promoting the advancement of herpetology in Texas by professionals and amateurs since 1939.

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CONTENTS Foreword by Laurie J. Vitt Acknowledgments xv

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Introduction 1 What Is a Lizard? 4 Natural History 6 Activity and Seasonality 6 Reproduction 7 Behavior 9 Conservation 23 Texas Biogeography and Landforms 23 Habitat Loss 35 Pollution 39 Climate Change 40 Introduced Species 41 Collecting and Trade as a Cause of Decline Observing and Collecting Lizards 44 Observing Lizards 45 Photographing Lizards 47

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Collecting Lizards 50 Legal Aspects of Collecting Lizards 53 Permits and Collecting Lizards in Texas 55 Threatened, Endangered, or Protected Nongame Species Maintenance of Lizards 56 Maintaining Lizards in Captivity 56 Creating Lizard Habitat 58 Handling Lizards 60 Museum and Preserved Lizard Specimens 61 Scientific and Common Names 61

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Dichotomous Key to Texas Lizards 71 Dichotomous Keys 71 Key to Texas Lizards 73 Systematic Accounts 83 Order Squamata, Suborder Iguania 85 Family Crotaphytidae 86 Eastern Collared Lizard (Crotaphytus collaris) 87 Reticulate Collared Lizard (Crotaphytus reticulatus) 91 Long-nosed Leopard Lizard (Gambelia wislizenii) 95 Family Iguanidae 99 Mexican Spiny-tailed Iguana (Ctenosaura pectinata); introduced species 100 Family Phrynosomatidae 103 Greater Earless Lizard (Cophosaurus texanus) 104 Spot-tailed Earless Lizard (Holbrookia lacerata) 108 Lesser Earless Lizard (Holbrookia maculata) 112 Keeled Earless Lizard (Holbrookia propinqua) 116 Texas Horned Lizard (Phrynosoma cornutum) 120 Greater Short-horned Lizard (Phrynosoma hernandesi) 125 Round-tailed Horned Lizard (Phrynosoma modestum) 129 Common Side-blotched Lizard (Uta stansburiana) 133 Ornate Tree Lizard (Urosaurus ornatus) 137 Rose-bellied Lizard (Sceloporus variabilis) 141 Canyon Lizard (Sceloporus merriami) 146 Mesquite Lizard (Sceloporus grammicus) 151 Dunes Sagebrush Lizard (Sceloporus arenicolus) 155 viii

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Eastern Fence Lizard complex (Sceloporus undulatus complex) 158 Texas Spiny Lizard (Sceloporus olivaceus) 165 Desert Spiny Lizard (Sceloporus magister) 170 Blue Spiny Lizard (Sceloporus cyanogenys) 174 Crevice Spiny Lizard (Sceloporus poinsetti) 178 Family Polychrotidae 182 Green Anole (Anolis carolinensis) 183 Brown Anole (Anolis sagrei); introduced species 187 Order Squamata, Suborder Scleroglossa 190 Infraorder Gekkota 191 Family Eublepharidae 192 Texas Banded Gecko (Coleonyx brevis) 193 Reticulated Gecko (Coleonyx reticulatus) 197 Family Gekkonidae 202 Rough-tailed Gecko (Cyrtopodion scabrum); introduced species 203 Common House Gecko (Hemidactylus frenatus); introduced species 205 Indo-Pacific House Gecko (Hemidactylus garnoti); introduced, unisexual species 208 Mediterranean Gecko (Hemidactylus turcicus); introduced species 211 Infraorder Scincomorpha 214 Family Scincidae 215 Coal Skink (Plestiodon anthracinus) 216 Prairie Skink (Plestiodon septentrionalis) 220 Four-lined Skink (Plestiodon tetragrammus) 223 Five-lined Skink (Plestiodon fasciatus) 227 Broad-headed Skink (Plestiodon laticeps) 231 Many-lined Skink (Plestiodon multivirgatus) 235 Great Plains Skink (Plestiodon obsoletus) 239 Ground Skink (Scincella lateralis) 244 Family Teiidae 247 Texas Spotted Whiptail (Aspidoscelis gularis) 249 Rusty-rumped Whiptail (Aspidoscelis septemvittata) 254 Little Striped Whiptail (Aspidoscelis inornata) 258 Marbled Whiptail (Aspidoscelis marmorata) 261 Six-lined Racerunner (Aspidoscelis sexlineata) 265 Gray Checkered Whiptail (Aspidoscelis dixoni); unisexual species 269

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Common Checkered Whiptail (Aspidoscelis tesselata); unisexual species 272 Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis); unisexual species 276 New Mexico Whiptail (Aspidoscelis neomexicana); unisexual species 280 Desert Grassland Whiptail (Aspidoscelis uniparens); unisexual species 284 Laredo Striped Whiptail (Aspidoscelis laredoensis); unisexual species 288 Infraorder Diploglossa 291 Family Anguidae 292 Texas Alligator Lizard (Gerrhonotus infernalis) 293 Slender Glass Lizard (Ophisaurus attenuatus) 299 Appendix A: Species with Texas Records of Questionable Origin 303 Appendix B: Nonestablished Exotic Species 305 Appendix C: Lizard Informational Resources 309 Appendix D: Map of Texas Counties 313 Glossary 317 Bibliography 325 Index of Common Names 327 Index of Scientific Names 331

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FOREWORD Texas on All Fours, Laurie J. Vitt Lizards have been a solid and sustaining part of Texas history for nearly 200 million years, long before the emergence of humans as we know them today. During their evolutionary history, lizards have watched dinosaurs disappear, and mammals and birds diversify. Much more recently, they stood by as Native Americans populated the land, and even more recently as the French, Spaniards, and Mexicans laid claim to Texas. If lizards can wonder, they likely have wondered why two-legged, erect mammals think the land belongs to them. During this time, Texas Alligator Lizards have stalked the elevations in what became Big Bend National Park, male Greater Earless Lizards have long stood on rocks along dry waterways with their bodies revealing a rainbow of colors, and Texas Horned Lizards have squirted bad-tasting blood from their sinuses when grabbed by coyotes and other predators in the open flatlands. Some whiptail lizards have even developed the ability to produce genetically identical daughters by a process known as parthenogenesis—effectively, virgin birth—which increases their reproductive rate xi

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considerably. Lizards were likely even more confused when humans tapped into what was left from the early evolution of life on Earth, compacted and decomposed into the vast oil fields of the Permian Basin and the coalfields scattered across some forty counties. Land that was once part of their range rapidly became a maze of highways, cities, suburbs, and ranches, although lizards do not recognize property lines. One has to wonder whether Texas lizards still anticipate the vast annual migrations of American Bison that once crossed the land. At some point late in the history of humans and very late in the history of lizards, a small set of humans took an interest in these generally four-legged creatures. Some lizards could spend what seemed like hours perched motionless on a rock during the early morning, while others zipped around on the ground in the late morning, always looking back to see whether you were any closer. Fascination with lizards grew as it became apparent that many species of them existed, and each species lived its life a little differently from the others. Naturalists began describing the life cycles and habits of many species during the late nineteenth and early twentieth centuries. By the late twentieth century, lizards had caught the attention of biologists from every conceptual area. Behaviorists examined their use of coloration and posturing in social behavior, ecologists examined species interactions and foraging modes, evolutionary biologists constructed life tables (a method of quantifying the effect of agespecific birth and death rates on population stability), and physiologists began to recognize that these so-called cold-blooded creatures maintained relatively high and constant body temperatures by behavioral means. Evolutionary biologists using molecular techniques and morphologists seeking homologous structures determined that snakes arose within lizards and thus technically are a subgroup of what we call lizards. Lizards became model organisms for testing hypotheses in conceptual biology. What began as a fascination with lizards rapidly evolved into the use of lizards by scientists to examine basic processes relevant to all life on earth: the day of the lizard was not over by any stretch of the imagination. Factors leading to the widespread use of lizards in research include the following: lizards are often very abundant; most are small enough to handle safely; only two xii

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species are venomous (excluding snakes), and they do not occur in Texas; many can be captured or trapped easily; and many are amenable to experimental manipulation. For amateur naturalists, nature hounds, professional biologists, and serious research scientists, Texas offers the opportunity to observe lizard diversity like no other part of the country. An impressive diversity of whiptails (Aspidoscelis), horned lizards (Phrynosoma), scaly lizards or swifts (Sceloporus), skinks (Plestiodon and Scincella), and geckos (Coleonyx and the introduced genera Hemidactylus and Cyrtopodion), along with snakelike glass lizards (Ophisaurus) and seemingly fierce collared and leopard lizards (Crotaphytus and Gambelia), makes Texas a lizard lover’s paradise. For anyone wanting to compile a life list of lizards encountered, Texas is the place to start, and this compilation of information by the Hibbitts brothers, based on firsthand experience, is an excellent guide to this remarkable diversity. As a final note, we have to ask what the future holds for lizards, in Texas and elsewhere. Human activity may well relegate many species to the historical dustbin, which would be a sorrow to all lizard lovers. On the more positive side, history suggests that lizards will do just fine. Diversity will change through time, as it always has, and lizards will likely stand on the rubble of civilization, just as they stood in the footprints of the dinosaurs, wondering what all the commotion was about! Laurie J. Vitt George Lynn Cross Research Professor and Curator Emeritus Sam Noble Museum University of Oklahoma, Norman

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ACKNOWLEDGMENTS We express special thanks to our wives—Marla and Rachel Hibbitts—and to our daughters—Cheyenne, Holly, and Hattie Hibbitts—as well as to our parents—Terry and Diana Hibbitts—for their support of our interest in nature, especially reptiles and amphibians, which led to this book. Thanks are also necessary for their constant support during our work on this project. They allowed us to devote substantial amounts of time at home, on the road, and in the field to writing the text and collecting the photographs for this book. Marla in particular deserves special thanks; she undertook driving duties on a family vacation to Maine in order to allow Troy to write the bulk of the introduction to this book. Both of us are lifelong members of the Texas Herpetological Society and have attended THS spring field meets since we were small children. The THS was instrumental in fostering our interests in the field of herpetology and herpetological natural history. As a society, the THS serves as a bridge between amateur xv

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and professional herpetologists in Texas and encourages discussions and interactions between these two groups. We thank the professors of herpetology who have guided our educations: James R. Dixon, professor emeritus in the Department of Wildlife and Fisheries at Texas A&M University; Jonathan A. Campbell, chair of the Department of Biology at the University of Texas at Arlington; Lee Fitzgerald, professor of wildlife and fisheries sciences at Texas A&M University; and Martin J. Whiting, associate professor of behavioral and evolutionary ecology, Witwatersrand University, Johannesburg, Republic of South Africa. Each of these individuals contributed greatly and directly to our educations in herpetology, as well as acting as mentors and friends. We thank our reviewers, Lawrence C. Jones and Charlie Painter, whose suggestions were invaluable in getting the manuscript ready for print. Casey Kittrell, at the University of Texas Press, was an eager advocate for our work and was instrumental in paving the way for its publication. Photographs for this book in addition to those we took were contributed by Patrick Alexander, Bryan Box, Tim Burkhardt, Marla Hibbitts, Terry Hibbitts, Pierson Hill, Kevin Messenger, Scott Wahlberg, and Kenny Wray. Without their contributions, this work would be incompletely illustrated and substantially less useful as a field guide.

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TEXAS LIZARDS

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INTRODUCTION The lizards constitute a group of predominantly small, agile, mostly four-legged, tailed, scaled, and clawed vertebrates. They typically lay leathery amniotic eggs that have all the internal membranes familiar from chicken eggs. Recently, some of the live-bearing lizards have been found to have complex placental attachments not unlike those found in mammals. Lizards may occasionally be confused with salamanders, owing to similarities in general body form (small, four-legged, tailed, terrestrial vertebrates), but unlike lizards, salamanders have clawless toes and thin, moist, scaleless skin. Lizards may also be confused with snakes, particularly those elongate lizard species that either have short legs or lack legs entirely; and in fact, lizards and snakes are very closely related to one another. Herpetology is the study of lizards, snakes, amphisbaenians (specialized burrowing legless “lizards”), turtles, crocodilians, and amphibians, yet many of these groups are not closely related biologically and were historically grouped together mainly because of similar habits. 1

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Ground Skink, Scincella lateralis, Grant Parish, Louisiana. This species may occasionally be confused with a salamander.

Dwarf Salamander, Eurycea quadridigitata, San Augustine County, Texas. This species may occasionally be confused with a lizard.

Lizards occur worldwide (except in Antarctica), and are classified—along with snakes, amphisbaenians, and New Zealand’s tuatara—in the class Reptilia. Turtles and crocodilians, formerly grouped with lizards and snakes in Reptilia, are now understood to belong to separate classes, Chelonia and Croco2

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dylia. Lizards are further grouped with snakes and amphisbaenians in the order Squamata. Globally, approximately 5,600 species of lizards are currently recognized, of which approximately 115 naturally occur in the continental United States. Of these 115 or so species, 45 are native to Texas, and an additional 6 species have been introduced and become established in the wild.

Rusty-rumped Whiptail, Aspidoscelis septemvittata, Brewster County, Texas. A typical lizard.

Striped Whipsnake, Masticophis taeniatus, Presidio County, Texas. A typical snake.

Florida Worm Lizard, Rhineura floridana, Florida. A typical amphisbaenian. Photo by Pierson Hill. 3

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WHAT IS A LIZARD?

While this may seem like a simple question, it is complicated by lizards’ being closely related to snakes and amphisbaenians. Most lizards have a primitive tetrapod body plan—that is, they have 4 legs approximately equal in size, a distinct head, and a long tail. They have scaled bodies, and most are rather small, fast-moving, agile creatures that are most active during warm, sunny weather. All lizards are ectothermic, which means that they use environmental heat sources to control their body temperatures. Ectothermy may seem like a disadvantage at first glance (particularly coming from the perspective of an endothermic human), but ectothermy provides lizards with numerous advantages. Since lizards do not use food to generate body heat, they require less food per individual than a similarly sized endotherm. This allows them to survive in areas with less available food than would be necessary for an endotherm. As a result, they can live in greater population densities than would be possible for endotherms subsisting on the same food resources. Finally, ectothermy allows them to undergo long periods of inactivity without feeding, for example, during periods of drought or cold temperatures. The earliest lizard relatives appeared in the fossil record approximately 250 million years ago in the Upper Permian or Lower Triassic Period. Essentially modern lizards appeared around 140 million years ago during the later Jurassic. Early in lizards’ evolutionary history, 2 types of lizards evolved, the iguanians and the scleroglossans. Iguania includes familiar lizard species that have fleshy, short, mostly nonextendable tongues (true chameleons being notable exceptions). Scleroglossa includes animals that have extendable, forked tongues used for chemosensory purposes—that is, for “smelling” their environments. These 2 groups are today recognized by systematists—scientists who study the evolutionary relationships between organisms—as distinct suborders within Squamata. Iguanians include such familiar species as the Green Iguana (Iguana iguana), “true” chameleons (genus Chameleo), and Inland Bearded Dragons (Pogona vitticeps), as well as Texas species such as the Green Anole (Anolis carolinensis) and the Texas Horned Lizard (Phrynosoma cornutum). Scleroglossans include not only lizards, but also snakes and the legless, burrowing am4

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Texas Spiny Lizard, Sceloporus olivaceus, Hidalgo County, Texas. A typical iguanian lizard native to Texas.

Reticulated Gecko, Coleonyx reticulatus, Presidio County, Texas. A typical scleroglossan lizard native to Texas.

phisbaenians. Living scleroglossan lizards include recognizable species such as the giant Komodo Dragon (Varanus komodoensis) and the car-insurance-selling day geckos (genus Phelsuma), in addition to Texas species such as the Texas Banded Gecko (Coleonyx brevis), the Texas Spotted Whiptail (Aspidoscelis gularis), and the Ground Skink (Scincella lateralis). 5

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Iguanian lizards are primarily visual predators (although some species are herbivores); because they have a poorly developed sense of smell, they rely on sharp eyesight to detect prey. All iguanians are diurnal—active during daylight hours—and are therefore among the most visible lizard species. Most iguanians are “sit and wait” predators: they fi nd perches or hiding places from which they can watch for prey, then dash out and capture the prey with their mouths. Scleroglossan lizards are primarily predatory active foragers, that is, they move constantly through their environments in search of food. Very few scleroglossan lizards are herbivorous. Although most scleroglossan lizards have well-developed eyesight, many rely to a large extent on their sense of smell to locate prey items hidden from sight. In this feature, the scleroglossans show their close relationship to snakes, which search for food in much the same manner. In fact, snakes are descended from a group of subterranean scleroglossans that lost their limbs, a development that facilitated a burrowing existence. Snakes’ closest living relatives among the lizards are the monitor lizards (genus Varanus) of Africa, Australia, and Southeast Asia. The precise relationship between lizards and the legless amphisbaenian “lizards” remains poorly understood; some authorities consider amphisbaenians to be a type of lizard, while others place them in their own taxonomic group. NATURAL HISTORY

Activity and Seasonality

Most lizards (with the notable exception of the geckos) are active during the day, when heat from the sun is available to stimulate their activity. Although they are ectothermic, they are able to control their body temperatures behaviorally. On a cool, sunny morning, lizards can frequently be seen basking in direct sunlight, and in such situations, their body temperature may be several degrees higher than the air temperature. During the hottest parts of the day, lizards typically seek shaded areas and may periodically retreat to cool underground burrows and “dump” excess body heat by pressing their bodies against a cool substrate, thereby reducing their body temperature below ambient levels. Some species may avoid the hottest parts of the day altogether and seek such refuges until the evening (or the next 6

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morning) brings cooler temperatures. In addition, lizards are controlling their body temperature when they perch on hot surfaces with their toes, tails, and bodies elevated off the substrate, thus minimizing direct contact with the heat source. Some species of lizards pant—breathe with their mouths open—which causes evaporative cooling. Each species of lizard has a preferred range of temperatures. Forest-dwelling semifossorial (living sometimes underground; technical terms like this one are defined in the glossary) skinks (genus Plestiodon) generally try to maintain a body temperature of 20°C–27°C (70°F–80°F); desert-dwelling, surface-active whiptails (genus Aspidoscelis) may be most active at body temperatures of 36°C–40°C (97°F–104°F). Lizards’ activity is generally curtailed on cloudy days when sunlight is not available, unless temperatures are warm enough to promote activity. Very few lizards are active at temperatures below 15°C (60°F) unless they are able to elevate their body temperature above 20°C (70°F) behaviorally. Despite their preference for heat, even desert-adapted lizards will overheat if their body temperature exceeds about 45°C (113°F). This reliance on warm daytime temperatures and available sunlight, especially on cool days, means that lizards are most active during the spring, summer, and fall, and that their activity is curtailed in the winter. But even in winter, some lizards may be active if temperatures are warm enough and there is enough sunshine to allow for activity. A lizard’s dependence on moisture varies across species. Some forest-dwelling species, such as skinks, require water to drink, while some desert species, such as whiptails, get most of their water needs from the prey they eat. Lizards may drink directly from puddles of water, but more often can be seen drinking from water droplets such as dew or raindrops on grass, rock surfaces, or their own skins. Regardless of how much or little water a lizard needs to drink, periods of extended drought tend to curtail lizards’ activity—as vegetation withers, the insects upon which lizards depend for food begin to die from starvation, forcing lizards to retreat underground and become inactive. Reproduction

Most lizards lay amniotic eggs encased in a flexible, leathery shell. The amniotic egg is an important adaptation that long ago 7

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A female Texas Spiny Lizard, Sceloporus olivaceus, ovipositing in a burrow under a rock, Kinney County, Texas.

freed the ancestors of lizards (along with other reptiles, crocodilians, birds, and mammals) from a dependency on water for reproduction. The amniotic egg consists of an embryo surrounded by and connected to a series of membranes. These include the yolk, which serves as a reservoir of nutrients for the developing embryo; the allantois, which serves to contain metabolic wastes (in particular uric acid) produced by the developing embryo; the amnion, which encloses and protects the embryo; and the chorion, which lies directly beneath the egg shell and allows the exchange of respiratory gases between the embryo and the outside environment. The ability to store metabolic waste (toxic ammonia produced as a by-product of protein metabolism) as insoluble, nontoxic uric acid in the amniotic egg allowed lizards to live in arid environments, where the flushing of such wastes in a liquid form (such as the urea which is produced by mammals) increases the risk of dehydration. While most lizards lay amniotic eggs with flexible, leathery shells, some (such as geckos) lay eggs with hard shells. Other species of lizards (such as the Crevice Spiny Lizard, Sceloporus poinsetti) are live bearers, with the amniotic eggs being retained in the mother’s uterus until birth. Also, it has recently been discovered that many species of viviparous skinks have mammalian8

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like placental attachments. Interestingly, the ability to give birth rather than lay eggs evolved independently among many different groups of lizards. Although most lizards reproduce by way of sexual reproduction, in which sperm from a male lizard fertilizes the eggs of a female lizard following courtship and copulation, some species of Texas lizards reproduce asexually through a process known as parthenogenesis. This word, from Greek, and translated literally means “virgin birth.” In parthenogenetic species, all individuals are females, which produce offspring that are genetically identical clones of themselves. Interestingly, members of these species continue to actively engage in courtship and copulatory behaviors. Following egg laying, high levels of the hormone progesterone stimulate female lizards to behave like males. These male-acting females court other females and engage in a simulated copulation termed “pseudocopulation,” in which the maleacting female assumes the copulatory position with another female. This in turn helps to stimulate estrogen production in the female receiving such attention, thereby increasing her fertility. Parthenogenesis (along with pseudocopulation) is known in 6 of Texas’s whiptail species (genus Aspidoscelis). Parthenogenesis is known in the nonnative Indo-Pacific Gecko (Hemidactylus garnoti) too, although whether this species engages in pseudocopulation is unknown. Behavior

Animal behavior describes how an animal interacts with the environment and with individuals of its own species and others. Lizard behavior can be divided into 4 broad categories: thermoregulatory behavior, which involves controlling body temperature; reproductive behavior, which involves both attracting mates and competing with members of the same sex for the opportunity to mate; foraging behavior, which involves the search for food; and antipredator behavior, which involves avoiding becoming food for other animals. Thermoregulatory behavior among surface-active diurnal lizards revolves around controlling the animal’s exposure to sunlight and its contact with surfaces—such as the ground, rocks, and tree limbs—heated by sunlight. Nocturnal, fossorial, and semifossorial species typically must concern them9

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A female Rose-bellied Lizard, Sceloporus variabilis, basks in a patch of sunlight, Hidalgo County, Texas.

selves only with regulating their exposure to heated surfaces. A surface-active diurnal lizard typically begins its day shortly after sunrise by orienting its body in a way that maximizes its exposure to heating by sunlight. Many species have a structure in their skulls known as a “pineal eye,” which is light sensitive and has been shown to conduct heat from the sun directly to the brain. This allows for increased activity of the nervous system, which quickens a lizard’s reaction time to threats while the body is still warming up. Lizards with a pineal eye may orient their heads toward the sun before venturing out to bask in the sunlight. Fossorial or semifossorial species may increase their body temperature by moving underneath thin rocks or the loose bark of dead trees, where they absorb radiant heat indirectly— as the sunlight heats the surfaces of these objects, the undersides become warm and transmit heat to the lizard beneath by conduction. Once a lizard has reached a suitable body temperature, it is able to engage in other activities, but thermoregulatory behaviors will continue throughout the lizard’s activity period. As mentioned previously, each species has a range of optimal body temperatures, above or below which its life may be threatened. To avoid overheating, a lizard begins to avoid sunlight, 10

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first moving to shaded locations and confi ning the bulk of its activities here. If substrates become too hot, a lizard may elevate first its body, then its toes and tail off the substrate, reducing the amount of heat transmitted from the substrate to its body. A lizard may also engage in panting, opening its mouth to allow evaporative cooling across the moist linings of the oral cavity. Lizards may periodically retreat from the surface into burrows or cavities in trees, where they can press their bodies against these cooler substrates in order to conduct heat away from their bodies into the substrate. If the outside environment becomes too hot for activity, lizards typically retreat underground or within tree cavities until temperatures become more suitable. In many nocturnal species, many of these thermoregulatory patterns are reversed. At nightfall, ambient temperatures may remain above the lizards’ activity thresholds, and these species must wait until temperatures cool sufficiently to allow them to emerge and begin their activities. As the air temperature progressively cools during the night, the lizards must expend more and more effort to keep their body temperature elevated. Once temperatures become too cool for activity, they retreat into sheltered refuges until the next night.

A female Long-nosed Leopard Lizard, Gambelia wislizenii, elevates her body, toe tips, and tail off a warm substrate to minimize the transfer of heat into her body, Inyo County, California. 11

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Introduction

A male Canyon Lizard, Sceloporus merriami, engages in a territorial push-up display, Terrell County, Texas.

Reproductive behaviors may involve maintaining and defending a territory, competing with members of the same sex for opportunities to mate, attracting and courting a mate, avoiding the attention of unwanted suitors, copulating, laying eggs, and guarding nests. Reproductive activity may be seasonal: some species engage in most of their reproductive activity in the spring or fall, and others may engage in it throughout their seasonal activity period. Seasonally reproductive species typically produce a single clutch of eggs or litter of young, while species that breed throughout the year may produce as many as 3 or 4 clutches (or litters) during the active season. In some species, males defend a territory that may include the home ranges of one or more females. Males do so by a variety of means, including posturing and threat displays. If postures and displays do not deter an intruding conspecific male, a male may escalate his aggression to include physical combat. Such combat generally involves biting the limbs or head of the opposing male. The loser of such a confl ict generally is evicted from the territory. For some species, during the height of the reproductive season, most mature males in a population may be noticeably scarred, with bite marks present on their heads and bodies. In some cases, the damage may be severe enough to 12

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A male Green Anole, Anolis carolinensis, displays his dewlap in a territorial display, Hardin County, Texas.

hamper survival—the loss of toes or feet may impair climbing ability, and abrasions to the skin may cause desiccation. In some territorial species, some percentage of males may engage in alternate strategies such as sneaking into another’s territory in order to court and mate with a female there. Some nonterritorial species engage in mate guarding, in which a male attracts and defends a single female against other males. Males of nonterritorial species generally search for females as they go about their daily activities in the environment. These males may search for females by following the scent trails they leave behind, or they may encounter females as they go about the business of foraging. Nonterritoriality does not necessarily allow males of these species to avoid conflict with other males. If 2 males encounter a receptive female at the same time, they will engage in first ritual and then physical conflict to win access to the female. Behaviors that lizards use to attract a mate may include visual signals such as head bobs, “push-ups,” raising a crest or extending a dewlap, or displaying bright colors on the body. These sorts of behaviors are particularly common in territorial species. In other species, when a potential mate is encountered, a male may rub parts of his body against the female’s to stimulate 13

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Two male Rose-bellied Lizards, Sceloporus variabilis, engaging in territorial combat, Hidalgo County, Texas. Photo by Terry L. Hibbitts.

During breeding season, male Broadheaded Skinks, Plestiodon laticeps, often show multiple bite marks on their heads and bodies from physical combat with other males. Liberty County, Florida.

The bright orange coloration on the face, flanks, and tail of this Long-nosed Leopard Lizard, Gambelia wislizenii, indicates that it is gravid. Inyo County, California.

her to accept copulation. Unreceptive females may ignore the attentions of males and, if their attention becomes too persistent, may attempt to flee or even fight the suitors. In some species, unreceptive females may display bright colors, indicating either that they are unready to mate or that their eggs have already been fertilized and that they are currently gravid. During copulation, a male lizard must entice the female to 14

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elevate her pelvis and tail to allow the male to curl his pelvis and tail beneath her. This allows the male to insert one of his 2 hemipenes into the female’s cloaca. The male may grasp the female’s body with his limbs, mouth, or both. Mating postures are often fairly stereotypical for particular species or groups of species. For example, a male whiptail forms a loop around a female’s body, their cloacas in contact, with his body arched over the female’s hips and grasping her abdomen just in front of the opposite hip in his mouth. This copulatory position is mimicked by pseudocopulation in parthenogenetic species. Egg-laying behaviors run the gamut from simply depositing the eggs in a sheltered location to constructing a nest chamber in the soil, either beneath a suitable cover object or within a structure such as a decaying log. In many species, once the eggs are deposited, they are abandoned by the female, at which point she goes back to foraging and attempting to replenish body fat

A copulating pair of Green Anoles, Anolis carolinensis, Hidalgo County, Texas. 15

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A female Texas Alligator Lizard, Gerrhonotus infernalis, guards her nest of eggs, Nuevo León, Mexico.

A female Broad-headed Skink, Plestiodon laticeps, guards her nest of eggs, Franklin County, Florida.

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reserves depleted in the reproductive effort. In other species, females guard and tend their clutches of eggs, curling their bodies around the eggs to protect them from predators. In Texas, species that actively guard their nests include the Texas Alligator Lizard (Gerrhonotus infernalis) and the skinks (genus Plestiodon); most other species abandon their nests after oviposition.

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Lizards employ primarily 2 behavioral strategies of foraging: “sit and wait” and “active searching,” however these strategies fall at the ends of a continuum, with some groups of lizards, such as geckos, falling somewhere between. A sit-and-wait strategy is adopted by most iguanian lizards and may also be employed at times by some geckos and skinks. Lizards that use a sit-and-wait strategy position themselves at a vantage point that offers not only a clear view of their surroundings but also a clear path on which to dash out and capture a prey animal. The vantage may be shielded from view or out in the open. The lizard waits for potential prey to come into range, at which point it may slowly inch toward the prey until striking distance is reached, or it may dash out to grab the prey. Active foragers, on the other hand, move through their environment, constantly probing in and around objects in search of prey. Whiptails, with their constant movement through the landscape, are prime examples of active foragers. Skinks and geckos may employ both sorts of strategies as they search for food. For example, the Mediterranean Gecko (Hemidactylus turcicus) often can be seen employing a sit-and-wait foraging strategy as it perches near a porch light while waiting for moths attracted to the light; after the lights are turned off, the same lizard may actively forage along the walls and eaves of the house.

A male Texas Spiny Lizard, Sceloporus olivaceus, preys upon a cicada, Kinney County, Texas.

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A female Long-nosed Leopard Lizard, Gambelia wislizenii, preys upon an adult male Zebra-tailed Lizard, Callisaurus draconoides, Yavapai County, Arizona.

Finally, lizards must try to avoid becoming prey for other species. Lizards are often cryptically colored and patterned, allowing them to blend in with their surroundings. Such species typically remain motionless to avoid initial detection. Upon discovery, such a lizard may make a short dash out of sight of the predator (or human observer) around a rock or tree limb, at which point it will freeze again and remain motionless until rediscovered. Many lizard species give warning displays to potential predators. Displays similar to those seen in territorial behavior or courtship, such as head bobs, push-ups, dewlap extension, or tail wagging (as seen in the Greater Earless Lizard, Cophosaurus texanus) are used to let a predator know that it has been seen by the lizard. Displaying to let a predator know that it has been seen is like the lizard saying to the predator that it cannot get close enough to make a successful predatory attack. On the other hand, the primary defense strategy for actively foraging species is evasion, which often means running at high speed to a refuge or just out of sight. Anyone who has tried to approach (to capture or photograph) a Marbled Whiptail (Aspidoscelis marmorata) in the Chihuahuan Desert can attest to this species’ ability to outrun at least one potential predator— humans! Other actively foraging species, such as most skinks, 18

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A Round-tailed Horned Lizard, Phrynosoma modestum, utilizes cryptic coloration to hide from predators (the lizard is resting at the base of the creosote in the bottom center of the photograph), Brewster County, Texas.

A Marbled Whiptail, Aspidoscelis marmorata, escapes predation by dashing into the cover of thorny bushes, Presidio County, Texas. 19

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A large lizard such as this Texas Alligator Lizard, Gerrhonotus infernalis, is capable of delivering a painful bite, Kerr County, Texas.

may restrict their activity to areas of dense vegetative cover so that they can quickly disappear into leaf litter or other vegetation when pursued by a potential predator. If a lizard is unsuccessful at avoiding a predator through one of the above behaviors, it may have other lines of defense. Many species, particularly large ones such as collared lizards (genus Crotaphytus), are capable of inflicting a painful bite that may cause some predators to release them. Once, while field collecting in the Rolling Plains of north-central Texas, one of our wives brought along her miniature pinscher. At one point during the day, an Eastern Collared Lizard (C. collaris) was discovered under a rock. When the rock was lifted, the lizard dashed out from cover and down the gravel county road, at which point the dog gave chase and grabbed the lizard. Almost immediately, the lizard turned and bit the dog in the face—the dog released the lizard with a painful yelp. Presumably, such a behavior would allow the same lizard to avoid predation from similarly sized wild predators as well. Species such as the Texas Horned Lizard (Phrynosoma cornutum), when grasped by predators, thrust their stiff spines into the mouths or paws of their attackers. If that does not deter the predator, some species of horned lizard may employ what is per20

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haps the most bizarre antipredator behavior seen in any lizard— squirting blood from their eyes. The lizard is able to voluntarily increase the blood pressure in the sinus behind one or both eyes, causing blood vessels to rupture, resulting in a directed stream of blood jetting from the corner of the eye socket. The eyes can be seen to bulge out from the head just before release of the blood, and the lizard is capable of directing the stream of blood very accurately, typically aiming for the eyes or face of a potential predator. The lizard is capable of jetting only 1 or 2 squirts per eye in a single encounter. It is not known precisely what effect this blood has on a predator—to a human, it does not sting or burn and has only a slightly salty, metallic taste. It is used by the lizards most often against canine predators. The taste of the squirted blood is distasteful to dogs and cats. Presumably, the predator releases the horned lizard as it attempts to get rid of the bad taste in its mouth. Perhaps the most well-known lizard antipredator behavior is the ability of many species to shed their tails. In most Texas lizards, if the tail is grasped by a predator, it will break off and continue to wriggle about. The predator is left holding the writhing tail in its mouth or paws while the lizard escapes. In some spe-

A Texas Horned Lizard, Phrynosoma cornutum, squirts blood from a sinus behind its eye, primarily in response to canid predators, Brewster County, Texas. Photo by Terry L. Hibbitts. 21

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A Madrean Alligator Lizard, Elgaria kingi, sheds its tail in response to a predation attempt, Grant County, New Mexico.

cies, the tail can be shed with minimal or no physical contact from a predator. Lizards with notoriously fragile tails include geckos (the Eublepharidae and Gekkonidae families) and the Western Slender Glass Lizard (Ophisaurus attenuatus). When the tail of a glass lizard, which in large specimens may exceed 50 cm (21 inches), breaks, it continues to thrash about. If it encounters resistance, such as from a stick or rock, it may break again, resulting in 2 separate pieces of tail thrashing about. Th is process may be repeated several times with each tail fragment, and a potential predator may be faced with several vigorously thrashing tail pieces while the lizard itself makes its escape. Because lizard predators often feed upon these shed pieces of tail, they may be thought of as something of a “bribe” by the lizard—the lizard gives up part or all of its tail to a predator, which the predator consumes. Tail loss by the lizard is not without cost, however, since the tail often contains valuable stores of fat and helps the lizard maintain balance during movement. Lizards that lose their tails easily typically will regenerate their lost tails. The regenerated tail section is shorter and stiffer than the original and usually of a different color; it lacks vertebrae and therefore lacks the fracture planes that gave the original tail its ability to break—it is instead supported by a stiff rod of car22

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tilage. Subsequent tail loss generally occurs above the original point of breakage on tails that have already been broken. Not all species demonstrate a dramatic ability to lose and regrow a tail—collared and leopard lizards (genera Crotaphytus and Gambelia), the Mexican Spiny-tailed Iguana (Ctenosaura pectinata), the horned lizards (genus Phrynosoma), and the earless lizards (genera Cophosaurus and Holbrookia) do not readily lose their tails and do not show strong abilities of regeneration when their tails are lost. CONSERVATION

At first glance, lizard populations may seem to be largely unaffected by human-caused changes to the landscape—after all, many species of lizards successfully inhabit and coexist with humans in urban or suburban settings. Most readers from East Texas are likely familiar with the Green Anole (Anolis carolinensis)—commonly and erroneously referred to as the “American Chameleon”; those from Central Texas undoubtedly have seen large Texas Spiny Lizards (Sceloporus olivaceus) climbing about on backyard oaks; and the introduced exotic Mediterranean Gecko (Hemidactylus turcicus) has become established on houses and buildings throughout the state. At the same time, older readers may also remember finding Texas Horned Lizards (Phrynosoma cornutum) throughout the eastern half of the state, a landscape from which this species has largely vanished over the past 30 years. Other species for which declines have been noted include Eastern Collared Lizards (Crotaphytus collaris) and 2 of the earless lizards (genus Holbrookia). One of these, the Spot-tailed Earless Lizard (Holbrookia lacerata), is almost certainly the most critically imperiled lizard species in Texas (maybe even the entire United States), having disappeared from over 95 percent of its former range. Causes of decline may include habitat loss, pollution, competition from introduced species, habitat changes due to introduced species, and global climate change. As with similar declines in most wild species, habitat loss is typically the most significant of these factors. Texas Biogeography and Landforms

The Texas landscape is extremely diverse, biogeographically, ranging from humid forests and swamps in the east to arid des23

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Figure 1. Ecoregions of Texas. 1. Piney Woods; 2. Gulf Coast Prairies and Marshes; 3. Post Oak Savannah; 4. Blackland Prairie; 5. Cross Timbers and Prairies; 6. South Texas Plains or Tamaulipan Thornscrub; 7. Edwards Plateau; 8. Rolling Plains; 9. High Plains; 10. Trans-Pecos.

ert flats and mountains in the west and from northern windswept plains where temperatures regularly plunge well below freezing in the winter to southern semitropical riparian thorn scrub where freezes may occur only once every twenty years. Although many factors help determine the specific features of a particular ecoregion, including soil type, the history of land use, and the frequency of fire, the most important are amount of annual rainfall and lowest winter temperature. Higher amounts of rainfall, in general, produce forests, while moderate amounts produce savannahs and grasslands, and limited amounts produce deserts. While most of Texas can be characterized as hot during the summer, winter presents a quite different story. In the High Plains of the Texas Panhandle, temperatures regularly dip down to −10°C (14°F) and snowfall is common; by comparison, in the Lower Rio Grande Valley near Brownsville, temperatures rarely reach 0°C (32°F) and snowfall is all but unheard of. These climatic extremes produce varied landscapes, each of 24

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which presents different challenges for Texas lizards. For convenience of discussion, the Texas landscape has been divided into 10 ecoregions, but it should be noted that these regions shade into one another along their boundaries, so habitat changes may be quite gradual as one travels from one ecoregion into another. Exceptions occur where the boundaries between ecoregions also correspond to dramatic changes in landscape—for example, the boundary between the High Plains and Rolling Plains is marked by the rugged rim of the Caprock formation, and the boundary between the Edwards Plateau and the South Texas Plains is marked by the Balcones Escarpment. A brief summary of Texas ecoregions is presented here. The Piney Woods occurs primarily along the Louisiana border, extending west to Montgomery and Houston Counties. This region receives the highest amount of annual rainfall in the state and supports a diverse assemblage of deciduous and evergreen trees. Historically, forest uplands were dominated by longleaf (Pinus palustris), shortleaf (Pinus echinata), and loblolly pine (Pinus taeda), a pattern maintained by frequent fires, which cleared out underbrush and removed competing hardwood species. In contrast, forest lowlands and river floodplains were dominated by oaks (genus Quercus) and other hardwood species.

This fire-managed area in the Angelina National Forest in Angelina County is similar to the naturally occurring forests encountered by the first Europeans to visit Texas. 25

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Only remnants of the formerly widespread Coastal Prairies remain, such as this site at the Attwater Prairie Chicken National Wildlife Refuge. Note the large area of brush encroachment toward the rear of the image.

The Gulf Coast Prairies and Marshes area occurs in a narrow band along the Gulf Coast. These areas can be characterized as grassy, sandy plains interspersed with freshwater, brackish, or saltwater marshes. The habitats extend inland from around 75  miles just west of Houston to as few as 10 miles along the coast in Kenedy County. In a narrow band west of the Piney Woods, from the Red River in the north and extending south to San Antonio, lies the Post Oak Savannah. Historically, this region was characterized by scattered stands of post oak (Quercus stellata) and blackjack oak (Quercus marilandica) interspersed with grasses such as little bluestem (Schizachyrium scoparium). Soils here are primarily sandy. As with the Piney Woods, these savannahs were historically maintained by fires, without which woody vegetation encroaches upon and chokes out areas of grasses, ultimately replacing a savannah with a woodland. Paralleling the Post Oak Savannah to the west is the Blackland Prairie. This is the southernmost extent of the tallgrass prairies that occur (or occurred) from central Illinois to the south through Missouri, eastern Kansas, and eastern Okla26

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homa. These moist prairies once supported stands of grasses and wildflowers “head high on a tall horse.” This ecosystem was maintained by frequent seasonal fires, which kept the encroachment of woody vegetation trees and shrubs at bay. The Blackland Prairie extends from Dallas County in the north to Bexar

An area of the Post Oak Savannah in Brazos County, showing dense undergrowth of yaupon holly, common in fire-suppressed areas.

This natural tallgrass prairie in Collin County, Texas, includes a high diversity of vegetation. Photo by Terry L. Hibbitts. 27

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Mixed post oak woodlands and prairies characterize the Cross Timbers region, as shown by this site in Young County. Photo by Bryan Box.

County in the south. Soils in the Blackland Prairie are a nearly black, rich loam full of organic materials, typically overlying a caliche and limestone bedrock. Occupying much of north-central Texas west of the Blackland Prairie and north of the Edwards Plateau is the Cross Timbers and Prairies ecoregion. In vegetative characteristics, this region resembles the Post Oak Savannah, but the soils are much rockier, consisting of varied areas of limestone and sandstone outcrops. The area of Texas south of Interstate Highway 10 and US Highway 90 is referred to as the South Texas Plains or the Tamaulipan Thornscrub. Historically, the region was characterized as a dry grassy plain with scattered mesquite (Prosopis glandulosa) thickets. But as a result of overgrazing and fi re suppression, the plains have been increasingly encroached on by thorny scrub, to the point that the landscape today is best characterized as a thorn scrub. The semitropical riparian forests in the Lower Rio Grande Valley (Starr, Hidalgo, and Cameron Counties) are sometimes considered distinct ecologically, since many tropical species (notably, of birds and butterflies) reach the northern limits of their distributions in this area. The Edwards Plateau region encompasses the core of Central 28

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Typical thorn-scrub-encroached grassland in Dimmitt County.

Riparian forests along the Rio Grande in extreme South Texas can be quite dense and have a distinctly tropical air. Vegetation includes Texas sabal palm, Texas ebony, and other subtropical trees. Sabal Palm Sanctuary, Cameron County; photo by Scott Wahlberg.

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Limestone outcrops, Ashe juniper, and various species of oaks typify the canyons of the Edwards Plateau region, Edwards County.

Texas, extending from Austin in the east to Terrell County in the west. The area is dominated vegetatively by live oak (Quercus virginica) and Ashe juniper (Juniperus ashei). Formerly, these trees occurred in scattered stands or canyons with large areas of grasses between the groves of trees. As in most of the other regions discussed so far, this condition was maintained primarily by periodic fires; the suppression of such fires has allowed extensive encroachment of oaks and junipers onto the once-grassy landscape. The western edge of the Edwards Plateau shades very gradually into the Trans-Pecos region of the Chihuahuan Desert, particularly in Val Verde and Terrell Counties. Thick outcrops of limestone dominate the region, particularly in the canyons of the Balcones Escarpment, which marks the Edwards Plateau’s southern and eastern boundaries. The portion of the Edwards Plateau that extends west of the Pecos River is often referred to as the Stockton Plateau. Although geologically contiguous with the Edwards Plateau, it is ecologically a transitional area between the Edwards Plateau ecoregion and the TransPecos area of the Chihuahuan Desert to the west. North of the Edwards Plateau and west of the Cross Timbers and Prairies is the Rolling Plains ecoregion. It extends roughly from San Angelo northward to Wichita Falls on the east and 30

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west to the edge of the Caprock. It is characterized by low, rolling hills on limestone and sandstone substrates. Except along watercourses, the Rolling Plains were essentially treeless before settlement by cattle ranchers and farmers. Today, the landscape is increasingly encroached on by mesquite.

The Stockton Plateau shares many features with the Edwards Plateau, but is drier and is a transitional area between the Edwards Plateau to the east and the Chihuahuan Desert to the west. Val Verde County, Texas.

The Rolling Plains present a grass- and shrub-covered landscape with rock outcrops and covered hills, as at this site in Throckmorton County, Texas. Photo by Terry L. Hibbitts. 31

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This site on the High Plains in Randall County shows a relatively undisturbed view of the native grasslands that once covered the Texas Panhandle. Photo by Terry L. Hibbitts.

The western two-thirds of the Texas Panhandle is occupied by the High Plains, an ecoregion that extends north from Texas along the eastern flanks of the Rocky Mountains, continuing north into Canada. In Texas, the eastern boundary of the High Plains is marked by an abrupt escarpment called the Caprock, which separates the High Plains from the Rolling Plains. The High Plains were historically a flat, treeless short-grass prairie marked by scattered depressions seasonally fi lled with water. Today, the region has been largely converted to agricultural uses, and only remnants of the formerly vast prairies remain. The Pecos River drainage, from its confluence with the Rio Grande northwest of Del Rio and extending north to Red Bluff Reservoir in Reeves and Loving Counties, roughly marks the eastern boundary of the Trans-Pecos ecoregion, part of the Chihuahuan Desert. (The Chihuahuan Desert is vast, covering 140,000 square miles in parts of Arizona, New Mexico, Texas, and 5 Mexican states.) The ecoregion is difficult to characterize, not least because of the great elevational differences between desert flats and mountain peaks. Many authors use “TransPecos” to refer to the area encompassing both the Chihuahuan Desert flats and lower mountain slopes, along with the forested mountain peaks. 32

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Deserts are often characterized in introductory texts by their lack of rainfall (usually described as regions receiving less than 25 cm, or 10 in., of rain annually), but as with any geologicalbiological phenomenon, the reality is much more complex when examined more closely. Rather than defining a type of region by a precise amount of rainfall, it is more important to consider how precipitation is processed by the environment. Does precipitation run off quickly? Sink rapidly into porous soils? Evaporate quickly? Any of these conditions may limit the availability of water in the ecosystem and allow desert scrub vegetation to thrive in areas where the amount of rainfall might lead one to expect grasslands to occur. In much of the Trans-Pecos ecoregion, this is precisely the case—rainfall levels are sufficient to promote the development of grassland habitats, but rains are infrequent and flashy, evaporation is rapid, and soils are porous, allowing desert scrub to exist. In the mountains of the Trans-Pecos, forests of piñon (Pinus cembroides and Pinus edulis), alligator juniper (Juniperus deppeana), and oaks (Quercus) occur at middle and high elevations, and remnant stands of ponderosa pine (Pinus ponderosa), Douglas fir (Pseudotsuga menziesii), and quaking aspen (Populus tremuloides)—trees more typical of the Rocky Mountains to

Desert-grassland conditions persist at higher elevations in the Trans-Pecos, such as this site near Marathon, Brewster County, Texas. 33

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Lower-elevation sites in the Trans-Pecos have mostly had their grass cover replaced by creosote and cacti, as shown by this site near Redford, Presidio County, Texas.

Higher elevations of the Trans-Pecos mountains are characterized by stands of piñon, juniper, and, in sheltered sites, ponderosa pine, as shown at this site in the Davis Mountains, Jeff Davis County.

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the north—occur in some sheltered canyons and on the northern slopes of the highest peaks. These mountains receive higher seasonal rainfall totals than do the desert plains between the mountains, particularly in mid to late summer, which is associated with monsoonal weather patterns.

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Habitat Loss

Habitat loss encompasses a range of habitat-altering activities. Most people tend to think fi rst of wholesale alteration of entire ecosystems when thinking of habitat loss—activities such as strip-mining, the clear-cutting of a forest, or the bulldozing and leveling of a landscape to make way for a subdivision or other building project. But many forms of habitat loss are much subtler; for example, the replacement of native range grasses with grasses used in “improved pastures,” such as coastal bermuda, King Ranch bluestem, or buffelgrass. The most widespread yet overlooked cause of habitat alteration results from the suppression of natural fire cycles (more on this phenomenon later). Habitat loss or alteration affects species because they rely on their environments for the conditions necessary to their survival. While some species live in a wide range of environmental conditions and can therefore tolerate a great deal of alteration to their habitats, others are highly specialized, requiring very specific conditions to be present in order to survive. In such instances, very minor (to a human observer) environmental changes may result in local or widespread extirpation of a species from the landscape. Historically, the single largest alteration to Texas landscape occurred with the conversion of the Coastal and Blackland Prairies of Central Texas into farmland starting in the 1830s and progressing with increasing rapidity over the next 100 years. This change transformed what once was a natural tallgrass prairie, with a diverse assemblage of grasses and wildflowers, into a series of monocultures made up of wheat, sorghum, and cotton fields. Furthermore, suppression of fires has allowed fallow fields and pastures to become increasingly encroached upon by trees such as sugarberry, cedar elm, and mesquite. How these changes have affected the populations of lizards present in this ecosystem is largely unknown, since no studies of lizard diversity were conducted in these areas before the conversion to agriculture. Undoubtedly, there have been significant declines in grassland-adapted species (such as the Prairie Skink, Plestiodon septentrionalis, and the Slender Glass Lizard, Ophisaurus attenuatus), as well as changes in species composition as species adapted to life in trees (such as the Texas Spiny Lizard, Sceloporus olivaceus) have moved in to occupy the shrubby forests that have grown up along fencerows and in fallow fields.

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Most natural prairies in Texas have been converted to agricultural use, like this site in Hill County. Photo by Terry L. Hibbitts.

A second major change in Texas landscapes also began in the 1830s: mature hardwood and pine forests of the eastern third of the state were cut for both timber and conversion to pasturelands. While at first glance it may seem that significant stands of these forests still exist, closer examination reveals that the landscape has been dramatically altered from its natural condition. Virtually all of Texas’s forested lands consist of secondor third-growth stands of trees, many of which are less than 30 years old. The understories of such forests are much denser with shrubby vegetation than is found in a mature forest. Furthermore, many of these “forests” are in actuality little more than agricultural fields devoted to the production of a single crop—in this case, pine plantations producing wood pulp for paper mills. Finally, the active suppression of fi res in these forests has dramatically changed their characteristics. Much of the heart of the southeastern Texas pinelands once consisted of mature stands of longleaf and loblolly pines in which trees were widely spaced from one another, there was very little understory of oaks and brush, and the forest floor was carpeted with grasses. In fact, in many ways these forests could have been characterized as grasslands. These conditions were maintained by frequent, periodic summer wildfires that burned the litter of pine needles and summer-dried grasses without damaging ma36

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ture pines or growing young ones while also largely preventing the growth of hardwood trees. While the suppression of wildfires remains a necessity in a landscape where human habitation is scattered throughout the forest, fire suppression has negative consequences for humans as well—in a forest where significant underbrush and fuel is allowed to accumulate, fires that do occur are often quite catastrophic—as was seen in the Bastroparea fires of 2011. In fact, the suppression of natural wildfires can be implicated in dramatic habitat changes throughout the state. Most grassland and savannah habitats are kept free of brush by fires. Once, the Post Oak Savannah along the Interstate 45 corridor between the Piney Woods of Deep East Texas and the Blackland Prairie of Central Texas was characterized by widely spaced islands of oaks in a sea of grass. Much of the Edwards Plateau region showed similar characteristics. Today, both regions feature

Many of Texas’s native forests have been converted to pine plantations, such as this one in Angelina County. 37

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very dense forests of small oaks with a great deal of brushy undergrowth. In the Post Oak Savannah, the undergrowth is predominately shrubby plants such as yaupon holly, while on the Edwards Plateau, dense stands of Ashe juniper choke out the grass. South of San Antonio, the landscape is often referred to as “South Texas Brush Country.” Yet this brushy condition, so familiar to South Texas deer hunters, has existed for only the past 100 years or so and is a direct result of fire suppression coupled with overgrazing. The landscape once supported extensive stands of native grasses, and much of the brushy vegetation was confined to the immediate vicinity of watercourses. These changes in habitat, which began in the late 1800s, were likely the first nail in the coffi n for the grassland-adapted Spot-tailed Earless Lizard (Holbrookia lacerata), which once occurred on clay soils throughout the region. Habitat changes have occurred in the deserts of the TransPecos too. When the first settlers and ranchers ventured into the region in the 1870s and 1880s, they encountered vast grassy plains supporting migratory herds of pronghorn and bison. They brought with them herds of nonmigratory cattle. The cattle were stocked on the range in excess of the natural carrying capacity of the land, resulting in overgrazing and loss of the natural vegetative cover. That degradation of the landscape allowed for the encroachment of brushy desert-adapted species such as the creosote bush, a species that secretes chemicals directly into the soil in order to inhibit growth of other plant species, thus eliminating competition for limited water resources. Unless controlled by fires, the creosote bush prevents grasses from recolonizing the area. Landscape changes in the Trans-Pecos have likely resulted in dramatic changes in the species composition of lizard assemblages there. Populations of grassland-adapted species (such as the Lesser Earless Lizard, Holbrookia maculata, and the Many-lined Skink, Plestiodon multivirgatus) have declined or been reduced in distribution while populations of desert-adapted species (such as the Greater Earless Lizard, Cophosaurus texanus and the Marbled Whiptail, Aspidoscelis marmorata) have simultaneously increased in numbers and distribution. In fact, it has been further suggested that the evolution of at least some of the parthenogenetic all-female whiptail species may have resulted in part from these changes in habitat. 38

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These species have their origins in hybridization events, in some cases between desert-adapted and grassland-adapted species formerly isolated from each other by habitat associations—associations that broke down with the rapid conversion of the desert grasslands into more xeric conditions. The last ecosystem in Texas to be altered by human activities is the High Plains. Although the elimination of bison and the subsequent conversion of the landscape into ranchland resulted in some overgrazing and associated habitat changes, these impacts were not as severe in this region as in others. Wholesale changes to the landscape came only with the development of deep drilling and pumping technology in the 1930s, which allowed access to the Ogallala Aquifer. Natural grasslands and rangelands were converted into agricultural monocultures of wheat and cotton, which of course resulted in the elimination of native lizard species’ natural habitats. The most recent suite of wholesale habitat changes in Texas has been the development of major urban centers in Houston, the Dallas–Fort Worth metropolitan area, El Paso, San Antonio, Austin, and, most recently, the increasing urbanization of the entire Interstate 35 corridor from Dallas to San Antonio. While these changes undoubtedly have created habitats for species such as the house-dwelling Mediterranean Gecko (Hemidactylus turcicus), they have also eliminated a great deal of habitat for many other species, such as the Slender Glass Lizard (Ophisaurus attenuatus), which require largely undisturbed grassy areas through which to roam. Pollution

Much like mammals, lizards, with their mostly impermeable skins, are relatively tolerant of environmental pollutants that they may encounter directly. But they are susceptible to pollutants, such as pesticides, that may be applied to their prey: directly, by ingesting prey items that have been poisoned by pesticides, and indirectly, since pesticide application reduces or eliminates those prey species that make up a lizard’s food supply. Consequently, in rural areas, lizard population density and species diversity are typically highest in wild or ranch lands and lowest in pesticide-intensive agricultural areas (although it must be noted that habitat structure and diversity are also higher in 39

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wild and ranch lands, thus promoting lizard diversity and supporting higher population densities). In urban and suburban settings, yards that encourage insect populations through activities such as butterfly gardening (and that consequently use few or no pesticides) typically have higher populations of lizards, while manicured yards upon which pesticides are used indiscriminately typically have few or no lizards. A species for which pesticide use has been implicated in widespread lizard declines and extirpation is the iconic Texas Horned Lizard (Phrynosoma cornutum). The species depends upon harvester ants (genus Pogonomyrmex) for approximately 90 percent of its diet. It has been estimated that a single Texas Horned Lizard requires 18–20 ant colonies to support its dietary needs. Therefore, the targeted and indirect elimination of these ant colonies by pesticide use destroys the Texas Horned Lizard’s food supply. Although harvester ants are not generally considered pest species and are not often direct targets of pesticide application, the invasive imported red fire ants (Solenopsis invicta) are obnoxious pests and are targeted, often with indiscriminate and widely broadcast pesticides—the use of which has all but eliminated harvester ants from much of eastern Texas. Consequently, Texas Horned Lizards are rarely found east of Interstate 35. Oil and gas field development in Texas has directly affected a variety of lizard species, both in the heyday of oil field development after World War II and in the current oil and natural gas boom. Roads through oil and gas fields fragment lizard habitats, and chemical pollution from the fields has been implicated in the direct mortality of certain lizard species. Climate Change

Climatic change is a real, readily observable phenomenon that has been globally documented. Its effect on many lizard populations remains speculative, since relatively few studies have been funded to explore such effects. A few studies have been performed quite recently, with data typically spanning less than a decade—whereas climate change is a long-term phenomenon best evaluated over decades of observations. The consensus is that the effects of changing climates on lizard populations are complex, and may be positive for some species, negative for 40

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others. Lizard species reach their greatest diversity in desert regions, so as regional or global temperatures increase and desertification spreads, the geographic ranges and populations of some species may expand. Species associated with grasslands or other more mesic habitats may see their ranges contract and their populations decline as mesic habitats succumb to arid conditions. This general picture of how changing climates may affect lizard populations needs to be fleshed out with specific details. For example, many lizard species adapted to high elevations are showing declines; they are relatively cold adapted, but the cold montane temperatures to which they are adapted are getting warmer. In addition to thermoregulation problems for cool-adapted species, climate change may result in their coming into direct competition with species adapted to warmer climates, which are expanding their ranges into areas formerly unavailable to them because of cool temperatures. Desert-adapted lizards in many cases synchronize their reproductive cycles in such a way that the emergence of their offspring coincides with the arrival of late-summer rainfall. These rains promote the proliferation of small insects, which make up the primary prey of neonate lizards. In some cases, this reproductive synchronization may be genetically determined rather than triggered by environmental cues (or may be triggered by invariant environmental cues such as day length). In such cases, changes to seasonal rainfall patterns resulting from climate change may desynchronize the lizard’s reproductive cycles from rainfall cycles and therefore result in neonate lizards hatching at a time of low food availability. Introduced Species

Introduced species may affect lizard populations in several ways. Many introduced plant species physically alter the habitat upon which lizards depend. The Chinese tallow tree is an invasive exotic that is rapidly converting Texas’s remaining coastal prairies into brushy woodlands. Invasive range grasses such as coastal bermuda, King Ranch bluestem, and buffelgrass produce dense mats of grass cover that is quite different from the more clumped native grasses to which many native lizard species are adapted. 41

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A female Eastern Fence Lizard, Sceloporus undulatus complex, basks on a mound of red fire ants, Vernon Parish, Louisiana.

Introduced predators may present lizards with challenges that some species are ill adapted to avoid. Perhaps the most insidious exotic predator of lizards is one that many of us overlook but with which we are intimately familiar—domestic house cats. Both feral cats and their well-fed counterparts that people regard as pets may take a huge toll on lizard populations when allowed to roam free. The invasive and introduced red fire ants (Solenopsis invicta) have been implicated in the declines of some lizard species, but comparison baseline data of lizard population densities before the introduction of these ants is unavailable. It is thought that adult lizards are largely unaffected by fire ant predation, but that their nests and hatchlings are particularly susceptible to it. Other species may compete with lizards directly for access to food, shelter, and territory. Of particular interest are introduced lizard species that are closely related to a similarly adapted native species. One well-studied example of such a species pair involves the native Green Anole (Anolis carolinensis) and the introduced Brown Anole (Anolis sagrei). In the absence of Brown Anoles, Green Anoles may be encountered in their habitat from the ground to the treetops. But when faced with competi42

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tion from Brown Anoles, the Green Anole mostly abandons the ground and lower shrubs, retreating (or being forced) into the mid to upper branches of trees. This principle is known in ecological sciences as “competitive exclusion,” and has been shown to occur with various species of gecko also (families Eublepharidae and Gekkonidae).

The native Green Anole, Anolis carolinensis (top), may be competitively excluded from parts of its habitat by the introduced Brown Anole, Anolis sagrei (bottom), Hardin County, Texas, and Collier County, Florida.

43

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Collecting and Trade as a Cause of Decline

Although the collecting of lizards from the wild has been implicated in the declines of some species, the effects of collecting on most lizard species are either poorly known or completely unknown. Perhaps the most well-known case of collecting causing a reduction in local populations of lizards in Texas was the collection of Texas Horned Lizards (Phrynosoma cornutum) for the pet trade in the 1950s and 1960s, although even with this case, the specific effects of the removal of an estimated thousands of individuals from Texas remain unclear and undocumented. This was a particularly tragic case, since virtually all these lizards undoubtedly perished as their owners found themselves unable to supply them with their highly specific diet of harvester ants. The trade in this species was one of the first closed by the State of Texas, with the placement of it on the state’s threatened species list in the early 1970s. Today, only a few common native lizards are collected commercially for the pet trade (for example, Green Anoles are commonly sold at pet stores), and although there is concern that some rare species may be targeted for collection, the impacts or potential impacts of such collecting remain largely speculative—but should be studied further. Furthermore, many species of lizards reach sexual maturity in a single season and produce multiple clutches of eggs during the year, making their populations rather tolerant to collecting pressures. Today, through the tracking of commercial nongame dealers, we know that a few thousand native lizards (this total includes data for several species) enter the commercial trade annually (either as pets or as food items for snakes)—figures that at first glance may seem alarming, but that have been rather consistent since permitting was first implemented, suggesting a degree of sustainability for these highly prolific animals. OBSERVING AND COLLECTING LIZARDS

Observing and collecting lizards in the wild can be an enriching and rewarding activity, and one that brings people closer to nature and the environment. Th is field guide is written for those who want to go into the field, experience where lizards live, and observe them in their natural habitats. Although many people will choose to follow the National Park Service’s motto “Take only pictures,” others may choose to collect specimens for per44

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sonal observation in a captive setting. Captive husbandry of these specimens can be quite rewarding (if often quite challenging as well) and provides insights into the lives of these fascinating animals that cannot be gained in any other way. Collecting for such a purpose should not be discouraged as long as it is done responsibly and in moderation. Furthermore, collecting for the purpose of providing voucher specimens to academic museum collections is vital for furthering our understanding of temporal and spatial changes to overall lizard species and populations. In addition, museum voucher specimens represent valuable material that can be used in a variety of research programs, from investigating evolutionary relationships among lizards to documenting the historical distributions of species in the face of changing climatic conditions. Observing Lizards

To observe lizards, one must go where lizards live. Each species has unique behaviors and habitat requirements, and anyone hoping to observe a particular species must learn its behaviors and requirements. Tips for observing individual species may be noted in or gleaned from the species accounts. Some general guidelines are presented here. Most species of lizards in Texas are diurnal—that is, they are active primarily during the day. As previously noted, each species has a range of temperatures most suited to its level of activity—below this temperature range, lizards either will be inactive or may be found actively basking in an effort to elevate their body temperatures into their active temperature range. This “warm up” period offers a good opportunity to see a particular species in its habitat, since basking or inactive lizards often allow humans to approach relatively closely. But to truly appreciate a lizard’s activities, one must continue observing the lizard after it becomes warm enough to begin its foraging or territorial activities. Lizards will continue their activity until the air temperature rises beyond their tolerance level, at which point they will at least periodically seek shelter from the sun. On some days, particularly in the spring, temperatures may never warm enough to inhibit the activity of some species of lizards, making it possible to observe lizards all day. On cool or overcast days, particularly in the early spring, no 45

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lizards may be active on the surface. On these days, to observe lizards you will have to search underneath cover objects such as rocks, logs, tree bark, boards, sheets of corrugated roofing material, or even trash items such as cardboard boxes or roofing shingles. Carefully lift up the cover object and peer underneath. If temperatures are sufficiently cool, lizards may be observed in a dormant or near-dormant state under such cover. On warmer days, you may only get a glimpse of a warm lizard as it dashes out from under the cover object to seek shelter under another such object nearby. On occasion, that nearest cover object may well be the opening of your pants leg just above your ankle, and the lizard observer may experience a much closer encounter with the lizard than he intended as the lizard wedges itself between knee and inseam! When searching under cover objects, always take care to ensure that you replace the cover object— particularly rocks, logs, and bark—precisely as you found them. This means that you must know the limits of what you can and cannot lift—it is all too easy to attempt to lift a large rock, only to find that it is too large for you to control—and then to watch it slide downhill into a position from which it is impossible to reset into its original location. Loose bark on dead trees, both standing and fallen, may be lifted to reveal lizards. Although such loose bark often flakes away from the log by the end of a single season, care should still be taken to ensure that adequate shelter remains to allow lizards (and other animals) access to these hiding places for the remainder of the season. The breaking apart of logs should be discouraged except when obtaining specimens is of high scientific importance. Like their diurnal counterparts, nocturnal lizards may be observed under cover, as described above. But to observe these species in their active cycles, one must search for them at night with the aid of a bright flashlight. The development of lighting technology in the past 10 years has made this task easier and easier. Today, one need no longer carry a bulky flashlight running on 4 D-cell batteries to have a high-intensity light source— in fact, a modern, high-intensity light-emitting diode (LED) flashlight that fits in the palm of the hand may produce light 4 or 5 times as intense as the old D-cell varieties. With the aid of such light, one may search out the walls of houses, roadside rock cuts, or the desert flats for nocturnal gecko species. While doing 46

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this, one may encounter sleeping specimens of diurnal lizards at the tips of branches, wedged into crevices, or even sleeping out in the open upon the ground. Occasionally, searching at night may reveal an otherwise diurnally active lizard that has been disturbed by an attempted predation event. On several occasions, we have encountered and caught nocturnally active whiptails with obvious bite marks on their bodies from lizard-eating snakes, indicating that they very recently avoided predation. To enhance one’s knowledge of lizards, it is helpful to record your observations and other data in a journal. Location, date, time, temperature, percentage cloud cover, moon phase (for nocturnal observations), species, behavior, and number of individuals observed are the kinds of important information to maintain. Location data should be as specific as possible— latitude and longitude can be recorded from a handheld GPS unit or from careful examination of mapping programs such as Google Earth. This information can assist future searches for a particular species, allowing the observer to rely not on faulty memory but on documented data. Furthermore, the information contained in such journals can be used to assist researchers trying to understand and target local lizard populations. Photographing Lizards

Most of the photographs in this book were taken with a singlelens reflex (SLR) camera with a macro or telephoto lens and an accessory flash or flashes. Images taken before 2006 were shot with fi lm cameras, but all the more recent photos were taken with digital SLRs. Focal length for the macro lenses ranged from 90 mm to 105 mm, while telephoto focal lengths typically ranged from 200 mm to 400 mm. The use of flash allows images to be taken at a high F-stop, resulting in increased depth of field. Some of the posed photos were taken with 2 off-camera flashes mounted with diff users, and most of the in situ photographs were taken with ambient light, which may have been supplemented with a single flash—either an off-camera flash or the “pop-up” flash integral to the camera. When photographing a lizard that has been collected, the first consideration for a quality photograph is a suitable background. Moss beds, leaves, and other relatively simple, nonreflective surfaces allow the animal to stand out. Lizards should 47

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An example of the setup used for macro photography.

be posed in such a way that their faces point slightly toward the camera. Elongate lizards should be posed with their tails coiled either toward or away from the camera—otherwise, detail of the animal’s body cannot be seen clearly. To position the lizard, typically one must firmly grasp the lizard by the head, covering the eyes, and then position the body naturally. With practice, one can learn to release the lizard and then slowly position the camera for the photograph while the lizard opens its eyes and sits still for a few seconds before moving off. The help of a partner greatly simplifies the process. One consideration with particularly active species is how to prevent them from escaping while attempting a posed photograph. Perhaps the simplest way is to tie a monofi lament noose around the knee of one of their hind legs, position the noose so that it is hidden in the photograph (or if one is proficient with Photoshop, edit the noose out during photo processing), and then secure the noose to a fishing pole, rod, or other object. Another method is to create a naturalistic habitat in the bottom of a large washtub with walls high enough to prevent the lizard’s escape and then pose the lizard in it. Note that this method requires all captured lizards to be returned to camp or a vehicle for photography, owing to the difficulty of carrying such a tub into the field. 48

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Perhaps even more rewarding is to photograph lizards in the field with a telephoto lens as they go about their natural activities. When doing so, approach a lizard slowly and deliberately; rapid or jerky movements are likely to elicit a fl ight response. Carefully watch the lizard and look for changes in its body posture indicating that it is becoming nervous about your approach. Take photos throughout your approach: with digital photography, there is no fi lm to waste, and it may be possible to crop a distant shot into a respectable image. Initial, distant shots can be discarded if you are able to get better, closer images. Occasionally and with practice, you may find that some species allow you to approach close enough for in situ macro shots. It must be noted, however, that not all species can be photographed adequately without capture and posing—these species include especially wary animals such as the Marbled Whiptail (Aspidoscelis marmorata) as well as grassland and leaf-litter skinks such as the Great Plains Skink (Plestiodon obsoletus) and the Ground Skink (Scincella lateralis). One final note regarding photographs is that they are becoming increasingly more accepted for use as vouchers documenting the occurrence of a particular species in a particular location. Although a photograph conveys far less information than a physical specimen, and in many ways is a very inade-

A noose tied around hind leg of this lizard prevents its escape during a photo session. 49

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A telephoto lens is often necessary to get unposed photos of wary lizards. Photo by Terry L. Hibbitts.

quate substitute for a specimen, members of the general public are far more likely to take useful photographs than to prepare and preserve scientific specimens. Photography also provides the only legal means by which an individual lacking a permit may document the occurrence of a threatened or endangered species. Photographs, with accompanying data, can be submitted to an appropriate research museum database or an online database system such as the Herps of Texas project (part of iNaturalist.org) and may then be used to document the occurrence of a species at a particular time and location. Remember, if you encounter a species in an area where it has not been documented previously, it should be documented! If it is not documented, it is just a story! Collecting Lizards

Although collecting animals from the wild is becoming more and more controversial, we feel strongly that the decision to collect is a personal one (as long as collecting is done in a legal, responsible, and limited manner). Many people fi nd collecting for a personal captive collection to be more rewarding than purchasing a lizard from a store; maintaining an animal that has been caught in its natural environment often brings back mem50

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ories of the chase. With lizards, it is important to collect only those specimens that one understands, including their sometimes complex natural history, and whose dietary needs one is able to provide for. Further, it is important to observe local, state, and federal laws when collecting in the wild. In Texas, a collector of nongame species must have a permit issued by the state or federal government, or a Texas hunting license. Even with these permits, it is important to recognize that certain laws are strictly enforced and that some animals cannot be captured without additional state and federal permits. A beginning collector should become familiar with the relevant requirements by contacting the Texas Parks and Wildlife Department (TPWD; www.tpwd.state.tx.us) for more information. Lizards can often be collected by hand, provided one has good hand-eye coordination. If one spots a lizard to capture, approach stealthily. Once within striking range, quickly and adroitly reach out and snatch the lizard. When searching under cover objects, one may be able to catch a lizard that is taking refuge under the object, and such a lizard can be quickly grabbed. Bear in mind that when lift ing large objects, it may prove difficult to both manipulate the cover object while grabbing a lizard that has been uncovered underneath. In such instances, capture is greatly assisted by working with a partner. Use caution when searching under cover objects, since venomous snakes, scorpions, spiders, and stinging wasps may also use such objects as refuges. In many cases, lizards will not allow one to approach closely enough to capture them by hand. In these cases, capture is greatly assisted by the use of a “lizard noose.” Such a device can be quickly constructed from a fishing pole such as a telescoping panfishing rod designed for use without rod and reel. Make a sliding noose from monofi lament fishing line, dental floss, or thin copper wire and then tie it to the end of the fishing pole. To use the noose, approach the lizard with the pole extended. Loop the noose around the lizard’s head and give the pole a quick upward jerk (much like setting the hook while fishing) to close the noose and jerk the lizard up into the air. Quickly extract the lizard from the noose. Collecting in this way typically leaves the lizard unharmed, but care must be taken when the lizard is in thick vegetation, since the noose may overtighten if the lizard 51

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Wary lizards can often be captured by using a noose at the end of a fishing pole. Photos by Terry L. Hibbitts.

or the noose becomes entangled in the plants. Large-headed, spiny-scaled lizards are most easily captured in this manner. The narrow-headed, small-scaled whiptails and race runners (genus Aspidoscelis) are notably difficult to capture using this method—while they can often be noosed up and off the ground, they tend to very quickly wriggle out of the noose and escape. Again, working with a partner facilitates capture of these liz52

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ards. Once the noose has been successfully looped around the lizard’s head or body, a swift upward and diagonal motion brings the lizard off the ground. Swing the lizard into the body of your partner, who then grabs the dangling lizard before it can wriggle free. As a final note on collecting, the advantage of collecting lizards is that one group or another can be collected in Texas on all except the coldest days of the winter. Unlike snakes, which tend to retreat deep underground in winter, at least some lizards can be found near the surface under cover objects or basking on warm days throughout the year. For our university work, we collect voucher specimens for proof of location or season. We make these collections sparingly, and with complete scientific information recorded and archived. Usually, only 1 or 2 voucher specimens per study area or season or objective are required. For many museum collections, we generally attempt to find what are referred to as DOR (dead on road) individuals so that we will not have to kill an individual. Although more applicable to larger animals, such as snakes, than to smaller and more delicate lizards, fresh DOR specimens are often in good enough shape to be prepared for museum storage. In some instances, vouchered animals are kept alive by the collector or in a museum collection, and upon its natural expiration the animal is prepared and stored permanently in the collection. Although photographs may be vouchered, in most cases a specimen is preferred, since, as mentioned, it provides much more data than does a photograph. It is becoming increasingly important to take tissue samples for DNA work—and tissue should be taken before fi xation in preservation media. In all cases, a collector should keep copious field notes and make them available whenever possible to local herpetology groups for publication in newsletters when something new or noteworthy appears. Legal Aspects of Collecting Lizards

Texas has laws that apply to the collecting, trade, and importation of native nongame species, including lizards. In addition to state laws, local ordinances govern the collecting and keeping of certain lizard species. These laws vary according to locality and are frequently revised. It is important to know the city, 53

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county, state, and federal laws pertaining to the area where one is collecting. The legal aspects of collecting and maintaining animals become more complex when the activity involves importing lizards, purchasing imported animals, or moving animals from place to place. The following discussion does not cover laws or rules for importing foreign or exotic animals, since they really do not have a place in a field guide specific to Texas. But as mentioned earlier, it is important to keep in mind that introduced species can displace native species in their natural habitat if they are released or accidentally escape into the environment. We do not condone the purposeful introduction of nonnative species into Texas habitats. Legislation and regulations provide guidelines for collecting, dealing in, and maintaining reptiles and amphibians. Some of these laws protect rare and endangered species, some protect habitats, and some protect the keeper and the public. For anyone planning to collect lizards, it is vital to set limited objectives and know the relevant laws and guidelines before attempting to collect, import, or keep any lizards. There are several levels of legal jurisdiction. Ignoring any of them may result in a citation, a fine (if one is found guilty), or, in cases involving threatened and endangered species, jail. These levels of jurisdiction include the following. Local laws: These are laws passed by cities and counties. Most of these governments have ordinances concerning collecting or keeping lizards. Many ban private citizens from keeping certain types of reptiles (in particular, large or venomous snakes and lizards or invasive exotics). Check with the local governments before collecting or keeping lizards. The local humane society may be a logical place to begin. Follow this with a telephone call to the local animal control officer. Texas state laws: For the most part, the State of Texas requires anyone seeking to collect lizards for personal use to have a hunting license. Most species can be collected only for noncommercial purposes and in limited numbers (fewer than 6 individuals). Only a few species may be collected in excess of that figure, and then only with a commercial collecting permit. Further, only a limited number of lizard species may be collected 54

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for commercial purposes, and in all cases some form of commercial collecting permit is required. Contact the TPWD for additional details. Federal laws: Aside from regulating the collection of lizard species that it deems threatened or endangered, the U.S. government allows the states to regulate their own native species. But when a violation of state law involves the transport of animals across state lines, federal law (the Lacey Act) has been broken, meaning that federal law enforcement can take jurisdiction. The Lacey Act, which is administered by the Department of Agriculture, states that the acquisition of any plant or animal in violation of state law is likewise a violation of federal law. The “injurious wildlife” provisions of the Lacey Act concern such animals as mongooses, walking catfish, venomous snakes and lizards, and certain toxic amphibians. The Endangered Species Act protects rare and endangered animals. The U.S. Fish and Wildlife Service (Department of the Interior) in Washington, D.C., can provide a listing of currently recognized endangered amphibians and reptiles. Permits and Collecting Lizards in Texas

The permitting and legal issues of hunting and collecting lizards, as with other game and nongame animals, is always changing, so we recommend that the reader contact the TPWD for current information. The following points are taken from the guidelines in a recent set of Texas Parks and Wildlife Outdoor Annual: Hunting and Fishing Regulations (2011–2012): • Lizards are considered to be nongame animals. • A hunting license is required of any person, regardless of age, who hunts any animal or bird in this state (Texas). • A hunting license is required to take nonprotected lizards. Texas regulates the quantity of a nongame species that can be kept in captivity. Species not listed as threatened or endangered are on either the “White List” or the “Black List.” Species on the Black List may not be sold and may be kept only in quantities of 6 or fewer. Species on the White List may be sold, and 25 or fewer may be kept without a nongame dealer permit. The per55

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mit is needed when maintaining more than 25 White List animals or when selling such animals. In 2011, the Texas State Legislature adopted legislation legalizing the collection of native wildlife, including lizards, from public right-of-ways (reversing legislation passed in 2007). The legislation requires a collector to park completely off the pavement, wear a reflective vest with 144 square inches of reflective material on both front and back, and not shine lights from the vehicle to assist the search. Nothing in the legislation makes it illegal to search for lizard species to photograph, but it is likely that a lizard photographer will be suspected of collecting. When photographing lizards along right-of-ways at night, or when using a light to collect or photograph at night on public land, consider making a courtesy telephone call to the local game warden. In addition, we recommend that the reader refer to the current regulations regarding the status of resident and nonresident collectors, as well as the general hunting and fishing regulations that pertain to all wildlife users. For further questions or more information, contact the TPWD Law Enforcement office at its toll-free number, 1-800-792-1112, or 512-389-4800, Monday through Friday, 8:00 a.m. to 5:00 p.m. Threatened, Endangered, or Protected Nongame Species

It is unlawful for any person to hunt or collect threatened, endangered, or protected nongame species. Proper documentation must accompany goods, whether purchased or sold, made from threatened or endangered species. For a complete current list of threatened and endangered species, and regulations relating to breeding threatened and endangered species, contact the TPWD. Other, more encompassing federal or CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) regulations may apply as well, and any lizard hunter or collector should be aware of them. MAINTENANCE OF LIZARDS

Maintaining Lizards in Captivity

Maintaining lizards in captivity can be rewarding. They make fascinating pets, some species require only relatively small spaces, and some can be easily maintained in restricted homes, 56

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apartments, or offices. Others may be kept (by professionals) for scientific study or for conservation efforts. It must be noted that lizards in general tend to be more difficult to maintain in captivity than similar-sized snakes because lizards typically require much more frequent feeding as well as (for many species) daily exposure to full-spectrum light containing ultraviolet light. Ultraviolet light is necessary for the lizard’s skin cells to synthesize vitamin D, and vitamin D is necessary for the metabolism of calcium and the production of strong bones (humans produce vitamin D in a similar manner). Vitamin D may be applied to the lizard’s prey items as a nutritional supplement—and in fact should be for most captives. But supplementation will likely provide adequate levels of vitamin D only for nonbasking species, whereas active baskers will still require full-spectrum lighting in order to completely meet their needs. Only a relatively small number of lizard species are suitable for home vivarium culture. Many species, particularly some of the smaller lizards, feed upon invertebrate prey too small to be readily available to the hobbyist. Generally speaking, the most suitable lizard captives include the larger, generalist species, which in nature feed upon a wide variety of prey and are active at a wide range of temperatures. Simplest to maintain are nonbasking species such as the Great Plains Skink (Plestiodon obsoletus) or the Texas Alligator Lizard (Gerrhonotus infernalis), which do not require full-spectrum lighting. Other large species, such as Eastern Collared Lizards (Crotaphytus collaris), can be kept successfully if they are housed in large enclosures with suitable temperature gradients, full-spectrum lighting, and large quantities of diverse, vitamin-supplemented prey. Such an animal should be considered suitable only for advanced keepers with a detailed understanding of the lizard’s natural history. Lizards typically require housing in a larger enclosure than would be suitable for a similarly sized snake. Generally speaking, a diurnal, basking lizard’s enclosure should provide a temperature gradient ranging from the lower 20s Celsius (upper 70s Fahrenheit) on one end of the enclosure to a warm (up to 40 degrees Celsius, or 90+ degrees Fahrenheit), illuminated basking spot provided by an incandescent light bulb on the other end. While incandescent bulbs provide warmth and will attract a lizard to bask, they do not produce ultraviolet light, which must be 57

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provided by a fluorescent bulb. Since fluorescent bulbs do not provide enough heat to encourage the lizard to bask, both types of light must be used. Lizards may be kept in outdoor enclosures too. Setting up an escape-proof outdoor enclosure requires careful planning and typically consists of an enclosed pen with aluminum flashing buried in the ground along its walls—to prevent escape both by digging and by climbing the walls of the enclosure. The enclosure can be landscaped with rocks, logs, and native vegetation. To prevent predation on captive lizards by feral cats, raccoons, and birds, fencing or netting should cover the enclosure. Design plans for such an enclosure can be found both online and from resources pertaining to the keeping of the Australian Inland Bearded Dragon (Pogona vitticeps) and the Latin American Green Iguana (Iguana iguana). A collector planning to take animals for keeping at home should become familiar with the diseases and parasites that can accompany captured animals. References are available that give excellent presentations of causes and cures of these problems. Most lizards are insectivorous, and even large species such as the Eastern Collared Lizard (Crotaphytus collaris) can live their entire lives on a diet of insects, particularly crickets, and other invertebrates such as mealworms. Crickets and mealworms can be purchased at pet stores or from wholesale suppliers. The supplementation of an animal’s diet with wild insects can provide important nutrients that may be lacking from store-bought insects. But be aware that insects from around a house or yard might have been exposed to pesticides, herbicides, or fertilizers, which are harmful to lizards. Supplement with wild insects only if you can be sure that the insects are chemical free. Larger carnivorous species such as Eastern Collared Lizards, Long-nosed Leopard Lizards (Gambelia wislizenii), and Great Plains Skinks may feed upon newborn or young mice. Note that all these species will also prey upon smaller lizards, and that they therefore should not be housed with smaller species. A caretaker should search for specialized publications related to maintaining a specific species. Creating Lizard Habitat 58

An alternative to keeping lizards in captivity is to attract them to your yard by creating habitat suitable for them. In our expe-

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A backyard habitat consisting of rock walls and diverse vegetation can allow lizard populations to thrive.

Stacked firewood makes a suitable refuge for lizards in the backyard. Be sure to check wood carefully for sleeping lizards before burning.

rience, the single most important step to take in encouraging lizards into your yard is to prevent or discourage feral and domestic cats from using your yard. Feral cats can be trapped and taken to an animal shelter. Be sure to check local ordinances regarding feral cats, since some municipalities have enacted wellmeaning but misguided ordinances protecting them. We have

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noted significant increases in lizard numbers and species diversity in yards where the threat of feral cats has been removed. Landscaping that provides shelters for lizards, in the form of rocks, shrubs, trees, and woodpiles, provides shelter for their prey too. Gardens designed to attract butterflies have the added benefit of attracting prey that can be eaten by many lizard species. Abstain from the use of wholesale, broadcast pesticides. In the event that pest insects such as wasps or fi re ants invade your yard, use pesticides sparingly, and only those that specifically target these pests. Handling Lizards

The first, and only, rule of handling lizards is not to do it unless necessary. All lizards should be restrained as little as possible except for a good reason. If it is necessary to hold a lizard—as when collecting or when restraining one for health or sex determination—it is important to know the correct procedures and methods for doing so. Special care must be taken with many species in order to avoid breaking their tails, particularly the Texas Banded Gecko (Coleonyx brevis) and many skink species (genera Plestiodon and Scincella), the tails of which are particularly fragile. Also remember that larger species—such as the Eastern Collared Lizard, Texas Alligator Lizard, and Great Plains Skink—can deliver a painful bite. Specimens being held in the hand should be grasped fi rmly. Smaller specimens can be completely contained within a closed fist—however, since smaller specimens tend to be the most delicate, it is best, when possible, to transfer them to a small, clean plastic container or cloth collecting bag for transportation or examination. Larger specimens can be grasped around their bodies with one hand. Place the thumb on the top or side of the head, with the index finger wrapped around the underside of the head and the remaining fingers wrapped around the body, controlling the legs. Keeping the thumb and index fi nger in this position will control the head and prevent the lizard from biting. Never grasp a lizard by the tail, and when holding a lizard, ensure that the tail does not strike a hard object or become entangled. Special care must be taken when handling the exceptionally long-tailed Slender Glass Lizard. The last two-thirds of the lizard’s body is tail, so only the fi rst third should be grasped. 60

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Since these lizards tend to flail their tails about when grasped, they should, when possible, be transferred to a collecting bag or container with all due haste. In fact, when collecting one of these lizards, it is often possible to chase them directly into the open mouth of a large bag. Since the lizards can flail about within the collecting bag, they may shed their tails if they knock against a hard object outside the bag. Even when all these precautions are taken, a glass lizard may live up to its name and shed its tail. MUSEUM AND PRESERVED LIZARD SPECIMENS

We do not encourage private individuals to build a collection of preserved lizard specimens. Such specimens are of much greater value when housed in an active research museum and should be deposited in one. But public school teachers or nature center directors may find that keeping preserved examples of local species is useful for educational purposes. While a keeper or collector may occasionally preserve deceased captive specimens or those found DOR, we do not have a section devoted to preservation techniques. Many references cover these techniques in detail, but we recommend that any reader interested in contributing preserved specimens to a museum or a teaching collection visit a local university for advice from a professional museum curator. It is important to point out that scientific institutions are not necessarily interested in accepting specimens from unknown sources. Generally, a collector must develop a relationship with an institution before it will trust that the specimen was legally collected and that the accompanying information is accurate. In all cases, complete data on where and when a specimen was collected is of paramount importance to its value. SCIENTIFIC AND COMMON NAMES

Taxonomy is the field of biology that categorizes all living things into groups and assigns names to those groups. Originally, the field was primarily concerned with naming organisms in order to facilitate communication between biologists speaking different languages. Organisms and groups of organisms were assigned distinct names at different taxonomic levels, which range from the all-encompassing kingdom down through in61

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creasingly narrower levels of classification until the most specific level, the species, is reached. Biology students may remember learning “King Phillip Came Over For Great Spaghetti,” a mnemonic for kingdom, phylum, class, order, family, genus, and species. In recent years, as DNA and biochemical evidence has provided a deeper understanding of the relationships between bacteria and eukaryotic organisms (those whose cells have nuclei), the rank of domain has superseded kingdom at the top of the classification hierarchy. Perhaps most importantly, within this taxonomic system, every species of living thing has been assigned a scientific name consisting of the genus name and the specific epithet. This two-part scientific name is a unique combination that identifies a single species. An example best illustrates how this naming system works. The Texas Horned Lizard, a readily identifiable species found throughout the western half of Texas (and formerly throughout most of the state), is classified as follows: Domain: Eukarya (the group that includes organisms whose cells contain a nucleus) Kingdom: Animalia (the group that includes all animals) Phylum: Chordata (the group that includes vertebrates and closely related invertebrates) Class: Reptilia (the group of scaled, four-legged or legless vertebrates that includes lizards, snakes, amphisbaenians, and the tuatara as well as numerous extinct groups) Order: Squamata (the group that includes lizards, snakes, and amphisbaenians) Suborder: Iguania (the group that includes lizards that have mostly short, nonextendable tongues and that forage by using vision) Family: Phrynosomatidae (the group that includes the horned lizards, sand lizards, spiny lizards, and relatives) Genus: Phrynosoma (the group of horned lizards) Species: Phrynosoma cornutum (specific name for the Texas Horned Lizard) Notice that the species name includes the genus name. The specific epithet cornutum (meaning “horned”) is insufficient to completely identify the Texas Horned Lizard scientifically, just 62

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as “Robert” is insufficient to specifically identify a person; complete identification requires the addition of a last name such as “Smith.” While with human names, there may be multiple “Robert Smiths,” with scientific names there is only one Phrynosoma cornutum, and that name can be applied to only a single species. Also notice that the genus and species names are italicized. This reflects the origin of these words in Latin (in most cases). Latin was the language of scholars and scientists when the scientific classification system was first created, so it was natural for scientists to incorporate Latin in their naming systems, especially because their goal was to create names for organisms that all scientists could understand, regardless of their native tongue. Today, the system of biological nomenclature continues to use Latin or the Latinized versions of words from languages such as Greek, English, or Spanish. Names are assigned to species according to rules outlined in the International Commission on Zoological Nomenclature (ICZN). A scientific name is often followed by the name of its describer and the year in which the species description was published (for example, Sceloporus cyanogenys Cope, 1885), which indicates that the species, the Blue Spiny Lizard, was described by Edward Cope in 1885. If the name of the author appears in parentheses—for example, Plestiodon fasciatus (Linnaeus, 1758), the Five-lined Skink—this indicates that the species was originally recognized as belonging to a different genus (in this case, Eumeces). Some species may be divided into subspecies, sometimes referred to as “pattern classes” or “geographical variants.” A subspecies is a geographically identifiable subset of a species that can be identified through examination of the animal’s body pattern or morphology. Formerly, subspecies were thought to be “incipient species,” or populations “on their way” to becoming separate species. But examination of biochemical data in recent decades has made it clear that most named subspecies do not correspond closely to restrictions in gene flow between populations within the same species, and these populations typically intergrade broadly with neighboring geographic races. Geographic races may reflect localized adaptations to environmental conditions, but the mechanism for that is not well un63

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derstood. In Texas lizards, most described subspecies represent poorly defined slices of clinal variation within a species, and (for the most part) we have chosen to not include subspecies descriptions in our species accounts. While taxonomy may seem fairly straightforward, it is generally deemed desirable for the classification and naming of organisms to reflect our understanding of how those organisms are related to one another. The study of how organisms are related to one another is termed phylogenetic systematics, which uses the characteristics of organisms—including morphological, behavioral, or genetic features—to infer the relationships between populations within species of organisms, to infer relationships between different species of related organisms, and to infer relationships between different genera, families, and orders. Whereas the field of taxonomy is governed by a system of rules, phylogenetic systematics often seems quite chaotic to laypersons, since scientists may propose conflicting hypotheses regarding relationships between the groups that they study. Th is is, in fact, quite representative of the scientific process: over time, evidence will mount in favor of one hypothesis over others, and a better understanding of the relationships between organisms will result. Unfortunately, the process of phylogenetic systematics does not always lead to stability in taxonomy, and name changes can occur frequently. This process is often trivialized by categorizing phylogenetic systematists as either “lumpers” or “splitters.” Lumpers are those biologists who combine taxonomic groups under a single name, and “splitters” are those who split members of a single taxonomic group into 2 or more new categories. A third sort of systematists might be recognized: the “reshufflers,” those researchers who move named groups from one taxon to another. This is currently an exciting time to be a phylogenetic systematist; technological advances give researchers access to larger and larger fractions of organisms’ DNA, which in turn allows ever-increasing amounts of data to be used to infer relationships between groups of organisms. Consequently, the names of species are in a state of flux, and new taxonomic arrangements are regularly proposed. For lizards, the names that naturalists learned for species a decade ago have, in many cases, 64

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been changed to reflect science’s new understanding of phylogenetic relationships. These changes present as much a challenge for a fieldguide author as for an amateur naturalist interested in keeping track of animal names. To help everyone stay current, the Society for the Study of Amphibians and Reptiles (SSAR) publishes a standardized names list: Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, with Comments Regarding Confidence In Our Understanding (Crother, ed., 2012). Because of the near-constant changes in taxonomy, the list is updated periodically online at www.ssarherps.org/pages/comm_names/Index.php. Note that this is a list of standardized English names, and that the scientific names outlined within it are a reflection of the authors’ “confidence in understanding” of the relationships. While names lists are published by other sources in North America, the SSAR list is generally considered the most widely accepted one, and should be the starting point for anyone wishing to keep track of changes in taxonomy. For this field guide, the SSAR list was used as a primary reference, but we deviate from it in several areas. First, when we felt that insufficient evidence was used to support recent taxonomic changes, we chose a conservative approach and used the older taxonomic arrangement. Second, when we felt that the available evidence supports a nomenclatural change, but that the boundaries between 2 forms have been insufficiently delineated, we again chose a conservative approach and used the older taxonomic arrangement. Th ird, when we felt that the appellation of a name is in error, we presented the taxonomic arrangement— following the rules outlined in the ICZN—that, in our opinion, best reflects the current understanding of species relationships. Finally, in regard to “standardized” English names, we deviate from the list when an older name is more widely in use, when a new name is less informative than an older name, or when a standardized name is clumsy and tedious. In particular, we differ from the SSAR list in the following 5 respects: . Eastern Fence Lizard Complex (Sceloporus undulatus complex) Recent analyses of this group of lizards using primar65

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ily DNA data sets have revealed that populations of the wide-ranging species formerly recognized as Sceloporus undulatus is in fact a complex of species consisting of 4 or 5 distinct forms. Some of these populations are readily distinguished morphologically, yet some are not easily separated. In addition, the geographic boundaries between the different forms have not been clearly delineated. Currently, 2 forms have been described as occurring in Texas, the Prairie Lizard (Sceloporus consobrinus) and the Southwestern Fence Lizard (Sceloporus cowlesi). Roughly speaking, the former occurs throughout Texas east of the Trans-Pecos region, and the latter occurs in the Trans-Pecos. This geographic delineation is only approximate, and the 2 forms cannot be distinguished from each other without the use of DNA analysis. Until further research is conducted, we feel it best to regard these lizards as members of the Eastern Fence Lizard (Sceloporus undulatus) complex. . Desert Spiny Lizard (Sceloporus magister) Recent studies using DNA analyses have suggested that the wide-ranging southwestern populations of large spiny lizards long regarded as belonging to the species Sceloporus magister in fact represent 2 or 3 distinct species. Other research does not support this conclusion. It has been proposed that the Texas and Chihuahuan Desert populations belong to a separate species, the Twinspotted Spiny Lizard (Sceloporus bimaculosus). But aside from slight variations in coloration, this form is difficult to consistently distinguish from its western relatives in the Sonoran Desert of Arizona, and we feel that the currently available evidence does not merit recognizing Sceloporus bimaculosus as a distinct species. . Rusty-rumped Whiptail (Aspidoscelis septemvittata) There is a great deal of confusion in the herpetological literature regarding the specific identity of populations of these lizards. Recent work has treated them as being conspecific with the Texas Spotted Whiptail (Aspidoscelis gularis) or a Mexican species, the Plateau Spotted Whiptail (Aspidoscelis scalaris). Some work has suggested that all 3 forms belong to a single, wide-ranging species, 66

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while other work has shown the Texas Spotted Whiptail to be distinct from a Mexican Plateau Whiptail inclusive of the Rusty-rumped variety. In Texas, the available data clearly suggests that the Texas Spotted Whiptail and the Rusty-rumped Whiptail act as 2 distinct species, with only limited hybridization and gene flow between them. But data on the Mexican populations is far more ambiguous, owing mostly to a lack of sampling in the sparsely populated regions of that country where the geographic ranges of these 2 forms meet. Having observed and collected a small number of Rusty-rumped and Mexican Plateau Whiptails in Mexico, we think that these 2 forms are distinct, at least superficially, in that country as well. Therefore we regard the Rusty-rumped Whiptail as a distinct species. . Gray Checkered Whiptail (Aspidoscelis dixoni) In the 2012 edition of the SSAR list, this species is treated as a variant of the Common Checkered Whiptail (Aspidoscelis tesselata). The question of where to draw species boundaries in unisexual species presents a special conundrum for phylogenetic systematists (see the discussion below). The Grey Checkered Whiptail resulted from at least 3 distinct hybridization events, producing 3 unique pattern classes (A, B, and C), each of which is a group of readily identifiable ancestor-descendant populations. These 3 pattern class populations are phenotypically very similar to one another and are readily distinguishable from populations of the Common Checkered Whiptail. For this reason, we chose to treat the Gray Checkered Whiptail as a species distinct from the Common Checkered Whiptail. . As discussed briefly above, we chose to retain certain common names that are in widespread use in older studies rather than to adopt the new, standardized common names proposed in the SSAR list. Specifically: A. The Lesser Earless Lizard (Holbrookia maculata) is referred to as the “Common Lesser Earless Lizard” in the SSAR list. We fi nd this name to be rather tedious and redundant. The name “Lesser Earless Lizard” does not otherwise appear in the standardized 67

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B.

C.

D.

E.

F.

names for members of the genus Holbrookia, therefore the specific name “Lesser Earless Lizard” can be applied to the species Holbrookia maculata without the word “common” in front of it. The Mesquite Lizard (Sceloporus grammicus) is referred to as the “Graphic Spiny Lizard” in the SSAR list. Since virtually all members of the genus can be described as “graphic,” we find this new, standardized name to be of little descriptive value. While we recognize that the widely used common name “Mesquite Lizard” is a poor descriptor for this species in most of its geographic range in Latin America, where it rarely occurs on mesquite, it remains descriptive for Texas populations. The Reticulated Gecko (Coleonyx reticulatus) is referred to in the SSAR list as the “Reticulate Banded Gecko.” Since adults of this species are not noticeably banded, we find the inclusion of this descriptor into the standardized name to be misleading at best. The Five-lined Skink (Plestiodon fasciatus) is referred to as the “Common Five-lined Skink” in the SSAR list. In many regions where it occurs with other five-lined skinks, this species is emphatically not the most common five-lined skink. Therefore, the adjective “common” in the standardized name is not always a good descriptor, and we chose to retain the more widely used name “Five-lined Skink.” The Ground Skink (Scincella lateralis) is referred to as the “Little Brown Skink” in the SSAR list. True, it is a little brown skink. But the name “Ground Skink” has been used widely for this species, and is a good descriptor of this small woodland ground dweller. The Texas Spotted Whiptail (Aspidoscelis gularis) is referred to as the “Common Spotted Whiptail” in the SSAR list. In many areas of Texas, particularly in the Trans-Pecos, other spotted species of whiptails are more abundant than Aspidoscelis gularis, making the name “Common Spotted Whiptail” inaccurate. Furthermore, other species of spotted whiptails, such as the Chihuahuan Spotted Whiptail and the So-

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noran Spotted Whiptail, include geographic descriptors in their names. Therefore, retaining “Texas” in the common name for the spotted whiptail that occurs throughout much of Texas follows the pattern of indicating geographic affi nity in these lizard species. Readers of older field guides will note some recent name changes, particularly at the genus level, for many Texas lizard species. In particular, most Texas skinks were formerly assigned to the genus Eumeces and are now regarded as members of the genus Plestiodon. Similarly, the whiptails and race runners have long been regarded as belonging to the widespread genus Cnemidophorus (giving the lizards a collective vernacular name among herpetologists—“Cnemis”), but recently were assigned to the genus Aspidoscelis. In both of these cases, the older name was paraphyletic, that is, it did not include all members sharing a single common ancestor. In these situations, the systematist can create a huge genus that includes all members of a single common ancestor (“lumping”) or else split a formerly large genus into smaller genera that each includes all descendants of a single common ancestor. Both cases are taxonomically tenable, but the second case is generally considered to be more informative regarding relationships among the species involved. For example, all the whiptails and race runners now included in the genus Aspidoscelis are more closely related to one another than they are to their Central and South American cousins that have been retained in the genus Cnemidophorus. Similarly, the genus Eumeces once included skinks from throughout the world, many of them more closely related to members of other genera in geographic proximity than to species in the genus, which made use of the name Eumeces quite uninformative of the relationships among the lizards involved. Putting the American species into their own genus, Plestiodon, and restricting Eumeces to species from Eurasia was a way to indicate that all the American species are more closely related to one another than any of them are to skink species retained in Eumeces. One final taxonomic matter that must be addressed is the difficulty presented by unisexual species such as some of the whiptails (genus Aspidoscelis). A species is generally considered to contain freely interbreeding populations of genetically dis69

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tinct organisms. Within a species, a population is the ecological unit that undergoes evolutionary change, primarily in response to natural selection caused by environmental changes. Closely related populations typically exchange genes with one another, a process that unites the populations within a single species. Populations of unisexual organisms, since they do not interbreed, do not interact in this manner. In fact, these “species” represent assemblages of related populations descended from single female ancestors. In the most technical sense, each ancestor-descendant lineage could be considered a separate species. Such species would be indistinguishable from one another in the field, and rather than treat such indistinguishable species separately, systematists usually regard genetically very similar lineages as constituents of a single species. The case of unisexual whiptails is further complicated by the unique process that gave rise to these species. It has been shown that each unisexual form arose through hybridization between 2 or more sexual species. These hybridization events likely occurred multiple times. For example, the Laredo Striped Whiptail (Aspidoscelis laredoensis) consists of 3 distinct lineages, each descended from a unique hybridization event between a Texas Spotted Whiptail (Aspidoscelis gularis) and a Six-lined Racerunner (Aspidoscelis sexlineata). The 3 lineages are genetically very similar, and most systematists regard them as being members of a single species. Yet one must recognize that in these instances, the term “species” does not quite mean the same thing as it does when applied to sexually reproducing populations.

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DICHOTOMOUS KEY TO TEXAS LIZARDS DICHOTOMOUS KEYS

A dichotomous key is an identification tool used in science. Each step in the key has 2 possible results (“dichotomous” means “divided into 2 parts”) and is usually based on morphological characteristics, including shape, scalation, color, and pattern. Keys are most often made to help identify organisms at the species level, but they can be designed to identify them only at higher taxonomic levels. Constructing a usable key can be a daunting task. The goal is to produce a user-friendly key applicable in the laboratory and the field. The terminology used in keys can be very specific, and in many cases diagrams and glossaries are necessary to maneuver through a key easily. Our key (adapted from Dixon 2013) is designed to identify examples of living or freshly dead specimens at the species level. Therefore, there may be problems using the key to identify preserved animals, since preservatives make it difficult to move limbs, affect the size of the animal, change patterns and colors, and distort an animal’s natural stature. This key addresses 71

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Lizard head scales. Top left: Broad-headed Skink (Plestiodon laticeps); bottom left: Five-lined Skink (Plestiodon fasciatus); right: New Mexico Whiptail (Aspidoscelis neomexicana).

Lizard body scales. Clockwise from top left: granular scales, Long-nosed Leopard Lizard (Gambelia wislizenii); cycloid scales, Great Plains Skink (Plestiodon obsoletus); rectangular ventral scales, New Mexico Whiptail (Aspidoscelis neomexicana); keeled scales, Desert Spiny Lizard (Sceloporus magister).

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Lizard femoral pores: Long-nosed Leopard Lizard (Gambelia wislizenii).

Oblique scale rows: Great Plains Skink (Plestiodon obsoletus).

only native Texas species or well-documented established exotic species. KEY TO TEXAS LIZARDS

. a. 2 pairs of legs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 b. Legs absent . . . . . . . . . . . . . . . . . . . . . . Slender Glass Lizard Ophisaurus attenuatus 73

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Key to Texas Lizards

. a. Movable eyelids present. . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 b. Movable eyelids absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . a. Digits short, dilated; claws arising from above an expanded toe pad . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 b. Digits narrow, slender through entire length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rough-tailed Gecko Cyrtopodion scabrum . a. Dorsal surface of body covered with small granular scales or small granular scales interspersed with small rounded tubercles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 b. Dorsal surfaces of body covered with large angular tubercles interspersed with granular scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mediterranean Gecko Hemidactylus turcicus . a. Dorsal surface of body uniformly covered with small granules; dorsal surface of tail lacking tubercles; sides of tail fringed with small toothlike scales; tail dorsoventrally flattened . . . . . . . . . . .Indo-Pacific House Gecko Hemidactylus garnoti b. Dorsal surface of body covered with small rounded tubercles scattered among small granules, especially toward rear of body; tail with 6 rows of enlarged granules, not dorsoventrally flattened . . . . Common House Gecko Hemidactylus frenatus . a. Tail with all scales about equal in size . . . . . . . . . . . . . . . 7 b. Tails with whorls of enlarged scales separated by 1 complete and often 1 incomplete series of smaller scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mexican Spiny-tailed Iguana Ctenosaura pectinata . a. Scales around body equal in size, smooth and shiny . . . 8 b. Scales around body unequal in size, not smooth and shiny . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 . a. Supranasals present; both eyelids scaly . . . . . . . . . . . . . . 9 b. Supranasals absent; lower eyelid with transparent disk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ground Skink Scincella lateralis . a. Lateral scales parallel to dorsal rows . . . . . . . . . . . . . . . . 10 b. Lateral scales not parallel to dorsal rows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Great Plains Skink Plestiodon obsoletus 74

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Key to Texas Lizards

. a. Dorsolateral pale lines not involving third scale row (only) from median line . . . . . . . . . . . . . . . . . . . . . . . . . . .11 b. Dorsolateral pale lines absent or, if present, involving only third scale row from median line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Many-lined Skink Plestiodon multivirgatus . a. Dorsal pale lines (dorsolateral or medial) not evident on either neck or trunk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 b. Dorsal pale lines present on neck or trunk . . . . . . . . . . .13 . a. Postnasal present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 b. Postnasal absent . . . . . . . . . . . . . . . . . . . . Four-lined Skink Plestiodon tetragrammus . a. 2 relatively large postlabials; 4 supralabials anterior to subocular; size (snout-vent length) never greater than 85 mm (3.3 in.) . . . . . . . . . . . . . . . . . . . . . . Five-lined Skink Plestiodon fasciatus b. Postlabials absent, or if 1 or 2, relatively small; 5 supralabials anterior to subocular; size (snout-vent length) frequently greater than 85 mm (3.3 in.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Broad-headed Skink Plestiodon laticeps . a. Postnasal present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 b. Postnasal absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 . a. Pale lines absent on dorsal surface of head; body with or without median light line . . . . . . . . . . . . . . . . . . . . . . . . . 16 b. 2 pale lines on top of head, usually visible posterior to nuchals, where they unite into single line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Four-lined Skink Plestiodon tetragrammus . a. 1 postmental; limbs overlapping when adpressed except in very large females; dorsolateral pale lines not edged medially with black . . . . . . . . . . . . . . . . . . . . . . Coal Skink Plestiodon anthracinus b. 2 postmentals; limbs not overlapping or touching except in young; dorsolateral pale lines edged medially with black . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prairie Skink Plestiodon septentrionalis . a. 2 relatively large postlabials; 4 supralabials anterior to subocular; dorsolateral pale stripes involving third scale row from median line; lateral stripe passes di75

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Key to Texas Lizards

b.

. a. b.

. a. b. . a.

b. . a. b. . a. b. . a.

b.

. a. b.

rectly through middle of ear, not directed toward upperanterior margin of ear; size (snout-vent length) not greater than 85 mm (3.3 in.) . . . . . . . . . . Five-lined Skink Plestiodon fasciatus Postlabials absent or, if 1 or 2, relatively small; 5 supralabials anterior to subocular; dorsolateral pale stripes usually not involving third scale row from median line; lateral pale stripe reaching anterior border of the ear at its upper margin; size (snout-vent length) frequently greater than 85 mm (3.3 in.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Broad-headed Skink Plestiodon laticeps Lateral fold from head to hind leg absent . . . . . . . . . . . . 19 Lateral fold extending from head to hind leg present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Texas Alligator Lizard Gerrhonotus infernalis Head covered with small granular scales . . . . . . . . . . . . 20 Head covered with scales of different sizes . . . . . . . . . . 21 Dorsal tubercles present among the dorsal granules, most evident over the hips . . . . . . . . . .Reticulated Gecko Coleonyx reticulatus Dorsal tubercles absent . . . . . . . . . . .Texas Banded Gecko Coleonyx brevis Belly scales round and smaller than, equal to, or only lightly larger than dorsal scales . . . . . . . . . . . . . . . . . . . . 22 Belly scales rectangular, much larger than dorsal scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Femoral pores present . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Femoral pores absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Dewlap pink; specimen green in life, but occasionally brown or mottled green and brown . . . . . . . Green Anole Anolis carolinensis Dewlap orange-red with median white border; specimen brown in life, never green; possessing light middorsal stripe with dark brown half-moon circles along each side of the back . . . . . . . . . . . . . . . . . . . . . . . . . . . . Brown Anole Anolis sagrei Head with bony spines or projecting ridge . . . . . . . . . . 25 Head without bony spines or projecting ridge . . . . . . . 27

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Key to Texas Lizards

. a. Sides of belly with 1 or 2 fringelike rows of enlarged scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 b. Sides of belly without fringe of enlarged scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Round-tailed Horned Lizard Phrynosoma modestum . a. Sides of belly with 1 row of enlarged scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Greater Short-horned Lizard Phrynosoma hernandesi b. Sides of belly with 2 rows of enlarged scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Texas Horned Lizard Phrynosoma cornutum . a. Ear openings absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 b. Ear openings present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 . a. Tail rounded, not flattened horizontally; without broad black ventral tail bands (small spots may be present) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 b. Tail flattened horizontally, with broad black transverse bands below . . . . . . . . . . . . . . . . . . . Greater Earless Lizard Cophosaurus texanus . a. Black spots absent on ventral surface of tail . . . . . . . . . 30 b. Black spots present on ventral surface of tail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spot-tailed Earless Lizard Holbrookia lacerata . a. Scales keeled . . . . . . . . . . . . . . . . . . . Keeled Earless Lizard Holbrookia propinqua b. Scales without keels . . . . . . . . . . . . . Lesser Earless Lizard Holbrookia maculata . a. Transverse gular fold absent . . . . . . . . . . . . . . . . . . . . . . . 36 b. Transverse gular fold present . . . . . . . . . . . . . . . . . . . . . . 32 . a. Interparietal scale much smaller than ear opening; 9 or more supralabials from rostral to below center of eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 b. Interparietal scale much larger than ear opening; fewer than 9 supralabials from rostral to below center of eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 . a. No black bands on neck . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 b. 1 or 2 black bands on neck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Eastern Collared Lizard Crotaphytus collaris 77

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Key to Texas Lizards

. a. Head width equal to or greater than distance between ear and nostril . . . . . . . . . . . . . .Reticulate Collared Lizard Crotaphytus reticulatus b. Head width less than distance between ear and nostril . . . . . . . . . . . . . . . . . . . . . . . . . Long-nosed Leopard Lizard Gambelia wislizenii . a. Dorsal scale rows equal in size; supranasals separating nasals from internasals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Common Side-blotched Lizard Uta stansburiana b. 3 or more dorsal scale rows much larger than others; no scales between nasals and internasals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ornate Tree Lizard Urosaurus ornatus . a. Postfemoral dermal pocket absent; breeding males without pink belly patches . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 b. Postfemoral dermal pocket present; breeding males with pink belly patches . . . . . . . . . . . . . . . . .Rose-bellied Lizard Sceloporus variabilis . a. Lateral body scales large, overlapping, no rudimentary gular fold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 b. Lateral body scales small, granular, not overlapping; rudimentary gular fold on each side of neck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Canyon Lizard Sceloporus merriami . a. Supraoculars small, in a single or double row, variable in number; all separated from median head scales by 1 or 2 complete rows of small scales . . . . . . . . . . . . . . . . . . . . 39 b. Supraoculars very large, in a single row, usually 5 in number; the last 1 or 2 not separated from median head scales by row of small scales as are the other supraoculars . . . . . . . . . . . . . . . . . . . . . . . . . Desert Spiny Lizard Sceloporus magister . a. Broad black collar across neck and shoulders, bordered anteriorly and posteriorly by pale line . . . . . . . . . . . . . . 40 b. Distinct pale-bordered black collar absent . . . . . . . . . . 41 . a. Tail brightly white and black banded toward tip; supraoculars usually in 2 regular rows; median head scales usually divided irregularly . . . . . . . Crevice Spiny Lizard Sceloporus poinsetti 78

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Key to Texas Lizards

.

.

.

.

.

.

b. Tail indistinctly banded; supraoculars large, irregular, 1 or 2 scales divided; median head scales usually not subdivided . . . . . . . . . . . . . . . . . . . . . . . . . . . Blue Spiny Lizard Sceloporus cyanogenys a. Scales on posterior surface of thigh very small, granular, not overlapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 b. Scales on posterior surface of thigh usually large, always keeled and overlapping . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 a. Lateral nuchal scales much smaller than and well differentiated from dorsal nuchal scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Mesquite Lizard Sceloporus grammicus b. Lateral nuchal scales same size as dorsal nuchal scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dunes Sagebrush Lizard Sceloporus arenicolus a. Posterior surface of thigh nearly immaculate; body dorsolateral pale lines distinct; dorsal dark bars absent in males . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 b. Posterior surface of thigh with a broad longitudinal dark line; poorly defi ned body dorsolateral pale lines; dark dorsal crossbands visible in adult males . . . . . . . . . . . . . 45 a. Dorsal scales 28–33, average about 30; supraoculars large . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Texas Spiny Lizard Sceloporus olivaceus b. Dorsal scales 44–55, average about 50; supraoculars small . . . . . . . . . . . . . . . . . . . . . . . Dunes Sagebrush Lizard Sceloporus arenicolus a. Males without blue throat patches; vertical white shoulder mark with black anterior and posterior margins; dorsal scales 44–55, average about 50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dunes Sagebrush Lizard Sceloporus arenicolus b. Males usually with blue throat patches; vertical white shoulder mark without black edging; dorsal scales 35–47, average about 40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Eastern Fence Lizard Sceloporus undulatus complex a. Dorsal pattern of alternating dark and pale stripes; dark stripes with even edges, never with pale spots or bars in dark fields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 79

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Key to Texas Lizards

.

.

.

.

.

.

b. Dorsal pattern reticulated, with pale and dark stripes or bars; if alternating pale and dark stripes, then dark stripes (fields) invaded with light spots or bars . . . . . . . 50 a. Scales bordering gular area enlarged and angular . . . . 48 b. Scales bordering gular fold granular. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Little Striped Whiptail Aspidoscelis inornata a. Postantebranchial scales moderately enlarged and angular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 b. Postantebranchial scales granular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Six-lined Racerunner Aspidoscelis sexlineata a. Usually 6 pale stripes; ventral surface of tail greenish, no faint pale spots in dark field (El Paso area) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Desert Grassland Whiptail Aspidoscelis uniparens b. Usually 7 pale stripes; ventral surface of tail pinkish or whitish; faint pale spots occasionally present in dark fields (Rio Grande valley from Del Rio southward) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Laredo Striped Whiptail Aspidoscelis laredoensis a. Postantebranchial scales distinctly enlarged, larger than first supralabial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 b. Postantebranchial scales similar in size to surrounding scales, or only slightly enlarged, never larger than first supralabial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 a. Dorsolateral pale lines interrupted with white spots that either join the pale lines or are superimposed on them . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 b. Dorsolateral pale lines straight, with pale spots in dark fields between the pale lines . . . . Texas Spotted Whiptail Aspidoscelis gularis a. Dorsal pattern of distinct, straight pale lines, often with light spots superimposed on them, but not obscuring pale lines; gular region immaculate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chihuahuan Spotted Whiptail Aspidoscelis exsanguis b. Dorsal pattern of pale lines that tend to become broken or obscured posteriorly; pale spots often merging with

80

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Key to Texas Lizards

. a. b. . a.

b.

. a.

b.

pale lines; gular region orange with black flecks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Rusty-rumped Whiptail Aspidoscelis septemvittata Scales along gular fold conspicuously larger than adjacent gular scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Scales along gular fold not conspicuously larger than adjacent gular scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Dorsal pattern of 6 or 7 pale lines joined by transverse crossbars to form a checkerboard pattern; dorsal pattern appearing to have more dark areas than pale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Common Checkered Whiptail Aspidoscelis tesselata Dorsal pattern of 8 or more pale lines joined by transverse bars, often giving the appearance of more bars than lines; dorsal pattern appears to have more pale areas than dark areas . . . . . . . . . . Gray Checkered Whiptail Aspidoscelis dixoni Lateral midbody color pattern of pale and dark stripes; middorsal stripe wavy or zigzag; dark fields with faint pale spots . . . . . . . . . . . . . . . . . . . . . New Mexico Whiptail Aspidoscelis neomexicana Lateral midbody color pattern reticulated and, if stripes present, with lateral pale crossbars joining pale dorsal lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Marbled Whiptail Aspidoscelis marmorata

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SYSTEMATIC ACCOUNTS The following systematic accounts describe 2 suborders, 4 infraorders, 9 families, and 52 species. Suborders, infraorders, and families are described briefly. In the species accounts, there are detailed sections for size, description, similar species, distribution, natural history, reproduction, and comments and conservation. Note: Parentheses around the name of a describing author indicate that the genus name has changed since the original description was published. If the author who named a species placed it in the genus that is used today, that author’s name is given without parentheses. If 2 years are given after an author’s name—the second in quotation marks—the first year is the actual date of publication of the paper that described the species, and the second is the date specified in the paper itself.

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ORDER SQUAMATA Suborder Iguania The suborder (or infraorder) Iguania contains 2,057 species, of which 78 occur in North America north of the U.S.–Mexico border. Of these species, 22 are native to Texas, and 2 are introduced exotic species with populations that have become established in the wild. As a group, the iguanians are predominantly sit-and-wait or ambush predators, with a limited sense of smell and nonprotrusible, thick tongues. As adults, they range in size from about 2.5 centimeters (1 inch) up to nearly 2 meters (6 feet) in total length; native Texas species range from about 10 centimeters (4 inches) up to 45 centimeters (18 inches)—although the introduced Mexican Spiny-tailed Iguana can reach 1 meter (3 feet).

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Crotaphytidae

FAMILY CROTAPHYTIDAE

Members of the family Crotaphytidae are confi ned to Mexico and the south-central and southwestern United States. There are currently 12 recognized species, 8 of which occur in the United States, and 3 of these occur in Texas. The members of the Crotaphytidae are among the largest naturally occurring lizards, reaching lengths of 35–45 centimeters (14–18 inches), with stout bodies, long hind limbs and tails, and large heads with powerful jaws. Their tails do not readily break, as do those of most Texas lizards, and when the tail does break, it does not regenerate readily. These lizards frequently employ a bipedal mode of running, tucking the forelimbs against their bodies and running only on the hind limbs, with their tails acting as a counterbalance to their bodies. All lizards in this family are voracious predators that, in addition to insects, commonly include smaller lizards as prey and have been documented to cannibalize smaller members of their own species. These lizards are divided into 2 genera—the collared lizards (genus Crotaphytus) and the leopard lizards (genus Gambelia). Most of the 9 species of collared lizards are saxicolous (rock dwelling), although the Reticulated Collared Lizard of the South Texas brush country is anomalous, frequenting open, flat areas on clay or sandy soils. The 3 species of leopard lizards live on desert flats and have patterns consisting of varying leopard-like spots.

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Eastern Collared Lizard

Eastern Collared Lizard

Crotaphytus collaris (Say, 1823)

SIZE Snout-vent length may be up to 115 mm (4.5 inches), with a total length of up to 356 mm (14 inches). Males on average are larger than females. DESCRIPTION The Eastern Collared Lizard is a large-headed lizard, with the head noticeably distinct from its neck. Its stout body has a rather long tail, which, unlike the tail in many lizard species, does not break readily. The front legs are about half the length of the hind limbs. Its body is covered with numerous small, granular dorsal scales, giving it a somewhat velvety appearance. The ground color ranges from tan to bright green on

Eastern Collared Lizard, male, Burnet County, Texas. 87

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Crotaphytidae

Eastern Collared Lizard, female, Barton County, Kansas.

the body, and the head is typically tan in Texas populations (but may be bright yellow in populations outside Texas). The body is typically dotted with light spots and faint crossbands, and the head may be dotted lightly with darker spots. Two black collars are present around the neck, with the area between the collars whitish. The belly is white. Males are larger than females, and typically more brightly colored at maturity. Males in most Texas populations are distinctly greenish, and females are a lighter green or tan. When gravid, a female will develop bright orange spots on her flanks and neck—coloration thought to signal to males that the lizard has already been fertilized. SIMILAR SPECIES The geographic ranges of Texas’s 2 species of collared lizards do not overlap. The Eastern Collared Lizard can be distinguished from the Reticulate Collared Lizard by the presence of 2 well-developed nuchal collars, the presence of greenish coloration in most adult males (except in extreme western Texas) and some adult females, and by the absence of a netlike dorsal pattern enclosing scattered black spots. Long-nosed Leopard Lizards are similar in size and structure, but lack collars and have a dorsal pattern of leopard-like spots. Eastern Collared Lizards may be confused with Crevice Spiny Lizards (Sceloporus poinsetti), which have a single broad nuchal collar and are covered with large spiny scales quite unlike the tiny granu88

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Eastern Collared Lizard

lar scales of the Eastern Collared Lizard. The Desert Spiny Lizard (Sceloporus magister) has large pointed scales but only a dorsally interrupted nuchal collar. DISTRIBUTION The species ranges from the Ozark Plateau of Arkansas and Missouri to eastern Utah and central Arizona and south to San Luis Potosí, Mexico. In Texas, it occurs throughout most of the western two-thirds of the state, from the Dallas– Fort Worth metropolitan area south along Interstate Highway 35 to San Antonio. The distribution extends north of a line from San Antonio westward along the southern edge of the Balcones Escarpment. NATURAL HISTORY Eastern Collared Lizards prefer open areas with limited vegetation interspersed with large rocks. The species is most common in arid and semiarid regions; in the eastern portion of its range, it is restricted to the most open sites, avoiding areas with extensive brush and tree cover. Typically, these lizards perch on rocks and watch their surroundings for prey, which includes a variety of arthropods—including all manner of insects and spiders—and vertebrate prey, most notably smaller lizards, along with the occasional rodent and hatchling bird. Very alert and wary, Eastern Collared Lizards will dash under a nearby rock if approached too closely or too quickly. They are preyed upon by birds of prey, carnivorous mammals, snakes, and members of their own species. REPRODUCTION Females typically lay large clutches of eggs, with a maximum clutch size of 22 recorded, although clutches of 7–13 are more typical. Several clutches may be laid in a single summer. Length of incubation is temperature dependent, but typically lasts from 42–94 days. Hatchlings typically emerge in late summer or early fall. They are 75–90 mm (2.9–3.5 in.) in total length when they emerge from the eggs, and are fast-growing, usually reaching sexual maturity by the following spring. COMMENTS AND CONSERVATION The Eastern Collared Lizard is on the TPWD’s White List, meaning that it can be collected for commercial purposes. It prefers open rocky areas and is most common in the Rolling Plains region between Abilene and Wichita Falls. In some areas, the species has suffered declines associated with the encroachment of brush. In particular, it was once common in the southern and western parts of the Edwards Plateau. When ranching subsidies for angora goats were sus89

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Crotaphytidae

Eastern Collared Lizard, gravid female, Ochiltree County, Texas.

Eastern Collared Lizard, hatchling, Coahuila, Mexico. Photo by Tim Burkhardt.

pended in the late 1980s, most of the goats were removed from the landscape and much of the formerly open rangeland has been increasingly invaded by groves of juniper (which the voracious goats kept in check), closing the canopy and shading much of the landscape used by these lizards, making it unsuitable for their needs. 90

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Reticulate Collared Lizard

Reticulate Collared Lizard

Crotaphytus reticulatus Baird, 1858

SIZE Snout-vent length may be up to 137 mm (5.4 inches), with a total length of up to 425 mm (16.75 inches). Males on average are larger than females. DESCRIPTION Like its relative to the north, the Reticulate Collared Lizard is a large-headed, stout-bodied lizard with a long tail and 4 powerful legs, the hind legs being approximately twice the size of the forelimbs. Its head is distinct from its neck, and its jaws are powerful, making this lizard capable of a strong bite. The long tail is slightly flattened dorsoventrally and does not break readily. The body is covered with numerous small granular scales. The ground coloration is typically tan or brownish, with a network of fine reticulations surrounding the darker ground color. Within a few of these reticulations are distinct black spots roughly arranged in bands on the body. This is a collarless or indistinctly collared species, although typical specimens have a ring of black spots present in the neck region corresponding to the collar seen in other species of collared lizards. The ventral surfaces are yellowish. During breeding season, a male may be brightly suff used with a yellowish color on its head, neck, and forebody. As with other species in this family, gravid females develop bright orange spots on their flanks, neck, and head. SIMILAR SPECIES See the account for the Eastern Collared Lizard to distinguish it from that species. The co-occurring Blue Spiny Lizard (Sceloporus cyanogenys) has a single, broad, welldeveloped nuchal collar and enlarged, pointed dorsal scales, and occurs in a different habitat (trees and rocks rather than flat, open areas). 91

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Crotaphytidae

Reticulate Collared Lizard, male, McMullen County, Texas. Photo by Kenny Wray.

Reticulate Collared Lizard, female, Tamaulipas, Mexico. Photo by Tim Burkhardt.

The Reticulate Collared Lizard occurs along the Rio Grande from approximately Eagle Pass southward to just west of McAllen. It ranges as far east as the towns of Tilden and Freer. Nowhere is this species common in southwestern Texas. South of Texas, the species ranges into the adjacent Mexican states of Coahuila, Nuevo Leon, and Tamaulipas.

DISTRIBUTION

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Reticulate Collared Lizard

NATURAL HISTORY The Reticulate Collared Lizard prefers open, gravelly areas that are sparsely vegetated with scattered bushes. In its preference for open flats, it more closely resembles the Long-nosed Leopard Lizard (Gambelia wislizenii) than the Eastern Collared Lizard (Crotaphytus collaris). It uses stumps, logs, dirt clods, or infrequent rocks as perches from which to observe its surroundings and dash out to subdue its prey. Like the Eastern Collared Lizard, it feeds upon a wide variety of arthropods as well as small vertebrates such as other lizards, small snakes, mammals, and nestling birds. When threatened, it retreats to the security of bushes, brush piles, and mammal burrows such as those dug by kangaroo rats or armadillos. REPRODUCTION Much like the Eastern Collared Lizard, this species breeds in the spring and summer and may lay several clutches of eggs in a single season. Clutches average 8–11 eggs and take 60–90 days to hatch, depending upon incubation temperature. Hatchlings are 90–100 mm (3.5–3.9 in.) in total length upon emergence. They grow rapidly and typically reach sexual maturity by the following spring. COMMENTS AND CONSERVATION The Reticulate Collared Lizard is on the state’s list of threatened species and may not be collected without a scientific collecting permit. Despite statewide protec-

Reticulate Collared Lizard, juvenile, Jim Hogg County, Texas.

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Crotaphytidae

tion, it continues to decline dramatically both in numbers and in distribution. It is only infrequently encountered throughout most of its Texas range. Reasons for the decline are unknown, but it is likely that brush encroachment and the introduction of exotic range grasses have adversely affected its habitat.

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Long-nosed Leopard Lizard

Long-nosed Leopard Lizard

Gambelia wislizenii (Baird and Girard, 1852)

SIZE Snout-vent length may be up to 132 mm (5.25 inches), with a total length of up to 384 mm (15.2 inches). Females on average are larger than males. DESCRIPTION Th is is a stout-bodied species, with a large, elongated head distinct from its neck. It has a long tail, and the hind limbs are about twice the length of the forelimbs. The body is covered with a large number of small, granular scales. The ground color may be whitish, cream, tan, or light gray, and is liberally dotted with a large number of dark, leopard-like spots. The size of the

Long-nosed Leopard Lizard, male, Winkler County, Texas.

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Crotaphytidae

Long-nosed Leopard Lizard, gravid female, Doña Ana County, New Mexico. Photo by Patrick Alexander.

spots and the amount of ground color between the spots varies between individuals and between populations. The ground color itself may be lightly sprinkled with a fi ne dusting of light spots. The spots extend onto the head and flanks and may be more distinct on the tail and hind limbs than on the forebody. In addition, some individuals may have 6 or 7 narrow light crossbars between the spots. The ventral coloration is typically white or cream. As in the Eastern Collared Lizard (Crotaphytus collaris), females develop orange bars on their heads, necks, flanks, and the undersides of their tails when they are gravid. These colors can be quite striking. Hatchlings are spotted with orange and have light crossbars that are much more prominent than those in adults. SIMILAR SPECIES See the species account for the Eastern Collared Lizard to distinguish it from that species. No other cooccurring species is quite so large or has a leopard-like pattern of spots. Under poor viewing conditions, a large adult Marbled Whiptail (Aspidoscelis marmorata) could possibly be mistaken for a Long-nosed Leopard Lizard, but closer examination would reveal the whiptail to be either unpatterned or marked with a faintly reticulated pattern of stripes and bars, not spots. Further, the whiptail has a distinctly pointed snout, and its head is not 96

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Long-nosed Leopard Lizard

Long-nosed Leopard Lizard, hatchling, Doña Ana County, New Mexico. Photo by Patrick Alexander.

distinct from its body. The similarly large Desert Spiny Lizard (Sceloporus magister) is a brown, unspotted lizard with prominently large pointed scales. DISTRIBUTION The Long-nosed Leopard Lizard occurs primarily in the Trans-Pecos region of Texas, with an extension east of the Pecos into the Monahans Sandhills. It is absent from mountainous regions of the Trans-Pecos as well as from the Stockton Plateau. Very few records of this species exist from Texas, and any specimen documented outside the immediate vicinity of El Paso or Monahans is noteworthy. Outside Texas, it occurs between the Sierra Nevada of California to the west and the Rocky Mountains to the east, ranging north to Idaho and Oregon. In Mexico, it ranges south to extreme northern Zacatecas. NATURAL HISTORY The Long-nosed Leopard Lizard prefers open gravelly or sandy areas that are sparsely vegetated with scattered bushes. Unlike the collared lizards, it typically does not seek an elevated position from which to observe its surroundings, instead hiding in the dappled shade of a bush from which it can dash out to subdue its prey. Like the Eastern Collared Lizard, it feeds upon a wide variety of arthropods as well as small vertebrates such as other lizards, small snakes, mammals, and nestling birds. When threatened, it retreats to the security of bushes, 97

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Crotaphytidae

brush piles, and mammal burrows such as those dug by kangaroo rats. REPRODUCTION Southern populations of this species may breed several times during the spring or summer, and females lay clutches of 7–11 eggs on average; larger females produce a larger number of eggs. As with collared lizards, incubation takes 60– 90 days, depending upon temperature. Hatchlings emerge from the eggs in late summer or early fall at 100–130 mm (3.9–5.1 in.) in total length. They grow fast and reach sexual maturity by the following spring. COMMENTS AND CONSERVATION Th is species is on the TPWD Black List and may not be commercially collected. Its apparent rarity in Texas may simply be an artifact of limited public access to suitable habitat, or it may indicate that much of the Trans-Pecos is only marginally suitable as habitat for this species.

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Iguanidae

FAMILY IGUANIDAE

The Iguanidae consists of 38 species distributed from the American Southwest through tropical regions of Central and South America. There are 2 species native to the American Southwest; a further 5 nonnative species have become established at various warm locales in the southern United States, including 1 in Texas. Collectively, the iguanids are largely herbivorous, although insects make up significant proportions of the diets of the juveniles of most species. The smallest species of the Iguanidae are larger than most lizard species in other families native to North America; the largest iguanids include the largest lizard species native to the New World tropics.

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Iguanidae

Mexican Spiny-tailed Iguana

Ctenosaura pectinata (Wiegmann, 1834) Introduced species

SIZE Snout-vent length may be up to 348 mm (13.6 inches), with a total length of up to 1,220 mm (48 inches). Mature males are larger than females. DESCRIPTION The Mexican Spiny-tailed Iguana is a large species with a distinct head, thick body, strong legs, and a long, muscular tail. A raised crest of scales runs from the back of the head to the base of the tail. The body is covered with numerous small, smooth granular scales that are in stark contrast to the strongly keeled, pointed scales encircling the tail. The head and body are gray, tan, or light brown with poorly defi ned, darker crossbands.

Mexican Spiny-tailed Iguana, male, Pima County, Arizona. Photo by Terry L. Hibbitts. 10 0

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Mexican Spiny-tailed Iguana

Mexican Spiny-tailed Iguana, juvenile, Oaxaca, Mexico. Photo by Tim Burkhardt.

Typically, the head and tail are lighter in color than the body. Males show a greater degree of contrasting coloration than females. Juveniles are bright green with distinct crossbands and are quite unlike the adults in overall appearance. SIMILAR SPECIES No other similarly huge species occurs naturally or has been introduced in Texas. Several similar species in this genus occur in Mexico, and specimens of these species could possibly occur as escapees in Texas. The Mexican Spiny-tailed Iguana can be distinguished from these species by the complete dorsal crest. The bright green juveniles could be confused with the Green Iguana (Iguana iguana), which has not become established in Texas but which may occasionally be encountered as escapees from captivity. Green Iguanas have a complete crest of narrow triangular scales down their backs, including their tails, but lack a circular ring of spines girdling the tail. DISTRIBUTION Currently, populations of this species have become established only in the vicinity of Brownsville. It is native to the Pacific Coast of central and southern Mexico. NATURAL HISTORY The Mexican Spiny-tailed Iguana is herbivorous, feeding mostly on leaves and fruits, although occasional animal prey may be taken. Insects make up a substantially larger pro101

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Iguanidae

portion of the diets of juveniles than of adults. In their native range, they inhabit both dry and wet tropical forests and are chiefly terrestrial, seeking cover in rocky crevices, animal burrows, brush piles, and hollow tree trunks. In Texas, the species occurs in brushy suburban settings in the Lower Rio Grande Valley, occurring along canals, resacas, and vacant lots. REPRODUCTION Courtship and mating occur in the spring, and females lay 12–50 eggs (25–30 on average). Hatchlings are around 180 mm (7 inches) in total length and grow rapidly. Like most lizards, they may reach sexual maturity by the following spring. COMMENTS AND CONSERVATION Th is exotic species is not covered under laws pertaining to commercial trade in Texas, and so may be collected for sale in any numbers. Note, however, that a hunting license is still required to collect this species from the wild (in much the same way that a hunting license is required to hunt feral hogs or exotic ungulates). The existing population of this species appears to be very small and localized, and further introductions are strongly discouraged.

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Phrynosomatidae

FAMILY PHRYNOSOMATIDAE

The Phrynosomatidae includes 137 species of small to mediumsized New World lizards, approximately 40 of which occur in the United States (1 or more species are represented by species complexes). At least 18 species occur in Texas, 1 of which is part of a species complex that may represent 2 or more distinct species. Texas phrynosomatids include 4 species of earless lizards in the genera Cophosaurus and Holbrookia; 3 species of horned lizards of the genus Phrynosoma, closely related to but morphologically distinct from the earless lizards; 2 small, relatively primitive, and unspecialized brush and rock dwellers in the genera Uta and Urosaurus; and 9 species of rough-scaled lizards of the genus Sceloporus which live in a variety of habitats.

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Phrynosomatidae

Greater Earless Lizard

Cophosaurus texanus Troschel, 1852

SIZE Snout-vent length may be up to 83 mm (3.25 inches), with a total length of up to 181 mm (7.2 inches). Males are larger than females. DESCRIPTION Th is is a small-headed, flat-snouted lizard with a stout body and relatively short tail. The dorsoventrally flattened tail has conspicuous black bars on a white background on its underside. The lower jaw is recessed into the upper jaw, and there are no external ear openings—both features facilitate burrowing into loose sand. The body is covered with tiny granular scales. The ground color often roughly matches the substrate upon which the lizards live: those on light-colored limestone soils may be whitish or pale gray, and those on pink granitic soils may be pinkish or tan. The ventral surfaces are largely whitish.

Greater Earless Lizard, male, Presidio County, Texas.

Greater Earless Lizard, male, Lubbock County, Texas.

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Greater Earless Lizard

The body is liberally dotted with small light-colored spots. In males of some populations, the spots on the front two-thirds of the body may be suff used with orange, and the distal one-third of the body and tail may be suff used with pale green. Males in all populations have 2 black chevrons on the distal third of the body, extending from the ventral surface up onto the animal’s flanks. The chevrons are surrounded by brilliant blue or bluishgreen coloration on the ventral surfaces. In females, the throat and sides of the belly may be suff used with orange or pinkish coloration. Hatchlings are uniformly light gray or tan. SIMILAR SPECIES As the name of the Greater Earless Lizard implies, all other co-occurring earless lizards are considerably smaller as adults. These smaller species do not have black bands under their tails, or else the black bands are reduced to spots. In males of this species, the black bars on their flanks are much more extensive than in the smaller species, and are surrounded by blue on the ventral surface. In members of the genus Holbrookia that have such marks, the marks are usually indicated by paired black spots. Furthermore, most individuals in Holbrookia have a dorsal pattern of paired spots that is lacking in the Greater Earless Lizard. All other Texas lizards have external ear openings. DISTRIBUTION The Greater Earless Lizard occurs widely throughout the western two-thirds of the state and prefers rocky or gravelly soils. Populations of this species range across central New Mexico, primarily in the valleys of the Rio Grande and the

Greater Earless Lizard, female, Pecos County, Texas.

Greater Earless Lizard, venters, male and female, Burnet County, Texas. 10 5

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Phrynosomatidae

Greater Earless Lizard, male, Llano County, Texas.

Greater Earless Lizard, female, Llano County, Texas.

Pecos River, and into central Arizona. In Mexico, it occurs in Sonora, Chihuahua, Durango, Coahuila, Nuevo Leon, Tamaulipas, Zacatecas, and San Luis Potosí. NATURAL HISTORY The Greater Earless Lizard prefers open gravelly areas interspersed with rocks, brush, and other vegetation. Th is preference for open sites makes it common along gravel roadways and rocky riverbeds. It is an ambush predator that seeks el10 6

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Greater Earless Lizard

evated perches from which to survey its surroundings for prey, which are primarily insects. It is a distinctly heat-loving species, with active body temperatures ranging from 37°C to 41°C (98°F–106°F). Where sand is present, these lizards may burrow into sand at night to sleep; in the absence of sand, they often sleep on the gravelly surface of the ground. Furthermore, it cannot distinguish natural gravel surfaces from the pavement of rural roads, and it can commonly be found sleeping on the pavement, particularly in arid areas in southwestern Texas. REPRODUCTION Reproduction occurs throughout the late spring and summer. Females lay 3 or more clutches of 2–9 eggs during a single season. Hatchlings are small—a snout-vent length of 26–31 mm (1.0–1.2 in.)—with large heads. They grow rapidly, and may reach sexual maturity by the following spring. COMMENTS AND CONSERVATION Th is species is on TPWD’s White List and may be collected commercially with appropriate permits. Its populations seem to be stable or increasing in Texas. The genus Cophosaurus is only poorly differentiated from the genus Holbrookia.

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Phrynosomatidae

Spot-tailed Earless Lizard

Holbrookia lacerata Cope, 1880

SIZE Snout-vent length may be up to 71 mm (2.75 inches), with a total length of up to 152 mm (6 inches). Adult males and females are approximately the same size. DESCRIPTION Like other earless lizards, this is a small-headed lizard with a flattened snout, no external ear openings, a short, slightly dorsoventrally flattened body, and a short tail. The body is covered with numerous small granular scales, and the ground color dorsally is tan, brown, or olive. This is the most boldly spotted species of earless lizard, having 1 or 2 rows of paired dorsal spots down the back. These spots are a shade or 2

Spot-tailed Earless Lizard, male, Irion County, Texas. 10 8

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Spot-tailed Earless Lizard

Spot-tailed Earless Lizard, female, Sterling County, Texas. Photo by Marla P. Hibbitts.

darker than the basic color of the body, and each is surrounded by light coloration. The ventral surfaces are white, with a row of 6–7 round black spots beneath the tail. Males of this species lack the ventrolateral paired black spots surrounded by blue that may be seen in the other 2 species of the genus Holbrookia. During breeding season, the forebodies of females may become suffused with orange or yellow coloration. SIMILAR SPECIES Th is species is not known to overlap in distribution with the Lesser Earless Lizard (Holbrookia maculata). It may be distinguished from that species by its more well-defined dorsal spots as well as the single row of spots on the ventral surface of the tail. In South Texas, this species may occur in the same general areas with the Keeled Earless Lizard (Holbrookia propinqua), but is readily distinguished by habitat preferences: the Keeled Earless Lizard occurs on sandy soils, while the Spottailed Earless Lizard occurs on gravelly or rocky clay soils. It can be further distinguished by its more well-defi ned dorsal spots and the row of subcaudal spots under its tail. See the account for the Greater Earless Lizard for characteristics used to distinguish these 2 species. All other Texas lizards have external ear openings. DISTRIBUTION Th is species was formerly distributed from the vicinity of San Angelo southward through the Edwards Plateau 10 9

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Phrynosomatidae

Spot-tailed Earless Lizard, male, Crockett County, Texas.

and the South Texas brush country. Apparently extirpated from the vast majority of this range, it can commonly be encountered only on the short-grass plains near San Angelo in Concho, Tom Green, Sterling, Irion, and Crockett Counties. Outside Texas, the species has been recorded in the adjacent Mexican states of Coahuila, Nuevo Leon, and Tamaulipas, but the current status of those populations is unknown. NATURAL HISTORY Very little of this species’ natural history has been documented. It is active in the spring from April and May until cooler weather ensues in October or November. It feeds primarily upon small insects and arachnids. The Spot-tailed Earless Lizard is most commonly seen in natural prairie areas with minimal brush encroachment. A population recently discovered in South Texas uses a well-maintained and mown airplane runway with bare areas interspersed with short grass. Open areas of exposed soil, gravel, or rocks may be favored. It is most active in the early to mid morning—during the hottest part of the day, it retreats to the shade of overhanging grasses or herbaceous vegetation. REPRODUCTION Again, this life history data is poorly known. Breeding likely takes place in the late spring and early summer. Females presumably lay clutches of 4–12 eggs, and more than 1 clutch may be laid in a single season. Females show bright or110

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Spot-tailed Earless Lizard

ange coloration on their heads and flanks when gravid. Hatchlings are approximately 38 mm (1.5 inches) in total length. COMMENTS AND CONSERVATION Although this species has not been added to Texas’s list of threatened and endangered species, it is almost certainly the most critically imperiled lizard species in the state, having disappeared from at least 95 percent of the historic locations where it once occurred. It is protected from commercial exploitation as a member of TPWD’s Black List. The factors leading to this species’ decline remain conjectural. It is adapted to natural grasslands featuring gravely soils with native grasses and minimal brush encroachment. It is likely that landscape changes beginning with overgrazing and fire suppression (allowing brush encroachment), coupled with the introduction of exotic invasive range grasses such as King Ranch bluestem and buffelgrass, have rendered formerly suitable habitat completely inhospitable for this species.

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Phrynosomatidae

Lesser Earless Lizard

Holbrookia maculata Girard, 1851

SIZE Snout-vent length may be up to 70 mm (2.75 inches), with a total length of up to 130 mm (5.2 inches). Males and females are similarly sized. DESCRIPTION Like other earless lizards, this is a small-headed lizard with a flattened snout, no external ear openings, a short, slightly dorsoventrally flattened body, and a medium-length tail. It has numerous small, smooth granular scales on its body. The ventral surfaces are primarily white, including the underside of the tail. There are 2 dark spots or bars on the flanks that extend slightly onto both the dorsum and venter. In males,

Lesser Earless Lizard, male, Jeff Davis County, Texas. 112

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Lesser Earless Lizard

Lesser Earless Lizard, venter, male, Presidio County, Texas.

Lesser Earless Lizard, male, Andrews County, Texas.

the marks may be narrowly edged by blue coloration. The dorsal coloration and patterning in this species is quite variable, both between and within populations. The ground color may be brown, tan, greenish, or yellowish. The underlying pattern of 1 or 2 rows of paired dorsal spots may be relatively distinct in some individuals, faint in others, or obscured by light spots or faint stripes in others. Breeding and gravid females are suff used 113

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Phrynosomatidae

Lesser Earless Lizard, female, Cochran County, Texas.

with reddish orange on their flanks and necks and by yellow on the head. SIMILAR SPECIES Greater Earless Lizards are larger than Lesser Earless Lizards and have dark bars under the tail. The Spottailed Earless Lizard does not overlap in range with the Lesser Earless Lizard and has a row of dark spots under the tail. All other co-occurring lizards may be distinguished from the Lesser Earless Lizard by the possession of external ear openings (although these may be difficult to see in the field). The Common Side-blotched Lizard (Uta stansburiana) may be confused with the Lesser Earless Lizard, but has only a single dark spot on its flanks and has a tail that is typically longer than its snoutvent length. DISTRIBUTION Th is species formerly ranged north of the Colorado River and east of the Blackland Prairie region, with a disjunct population in the high grasslands of the Trans-Pecos. The species has apparently been extirpated from most of the Rolling Plains east of the High Plains, although a population has been recently discovered along the Red River in Oklahoma near Wichita Falls. Beyond Texas, this species occurs on the Great Plains north to southern South Dakota and Wyoming and west to Arizona and southeastern Utah. In Mexico, it occurs south to Zacatecas and San Luis Potosí. 114

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Lesser Earless Lizard

This species may be found in a wide range of habitats but prefers sandy soils that support flat or rolling grasslands. It eats primarily small insects, spiders, or other terrestrial arthropods. It is active from April until the arrival of cool temperatures in October or November. It is most active in the early morning, before temperatures get too hot, upon which time it may retreat beneath the sand to escape the midday heat. REPRODUCTION Breeding typically occurs from May to July, and females may reproduce more than once during this time. Clutches typically contain 4–6 eggs. Hatchlings are about 38 mm (1.5 inches) in total length. They grow rapidly and may reach sexual maturity by the following spring. COMMENTS AND CONSERVATION Populations of this species in the eastern part of its range have all but disappeared in recent decades. Despite this well-documented decline, the species remains on TPWD’s White List and may be commercially exploited. Populations in the Trans-Pecos occur in low densities but seem reasonably stable. The species remains locally common on the High Plains and in the Monahans Sandhills country. Declines have been linked to habitat changes associated with overgrazing. Because of its wide range and the substantial variation between populations, this species may represent a species complex. NATURAL HISTORY

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Phrynosomatidae

Keeled Earless Lizard

Holbrookia propinqua Baird and Girard, 1852

SIZE Snout-vent length may be up to 60 mm (2.4 inches), with a total length of up to 141 mm (5.75 inches). Males and females are approximately the same size. DESCRIPTION Th is species is another smallheaded, wedge-snouted lizard lacking external ears. Like the other earless lizards, it is slightly dorsoventrally flattened, with a countersunk lower jaw. The body is covered with small granular scales that—unlike those of other earless lizard species in Texas—are distinctly keeled (the scales are so small that a hand lens may be necessary to determine this). The tail is longer than the body. The ground color varies with substrate, but ranges from whitish to tan. Paired dorsal spots may be distinct or ob-

Keeled Earless Lizard, inland male, Dimmitt County, Texas. 116

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Keeled Earless Lizard

Keeled Earless Lizard, inland female, Wilson County, Texas.

scured. If present, they may be bordered in white on their posterior margins only. Specimens that occur inland typically show a fairly distinct pattern, while those present in coastal sand dunes are faintly marked and may appear whitish overall. There are 2 lateral black spots present on the flanks just in front of midbody. They are distinct in males and may be absent in females. These black spots are not bordered in blue. The belly is white, and the underside of the tail is unmarked. SIMILAR SPECIES Th is is typically the only earless lizard present in sandy habitats in South Texas. The rare Spot-tailed Earless Lizard occurs on clay soils and has a tail shorter than the body, smooth dorsal scales, and dark spots under the tail. The larger Greater Earless Lizard occurs on rocky or gravelly soils and has dark bars under the tail. Males of this species have black lateral bars that are distinctly surrounded by blue. All other cooccurring species have external ear openings and larger scales. DISTRIBUTION Th is species occurs in Texas on sandy soils south of San Antonio. It occurs in widely scattered populations, most commonly along coastal dunes from Corpus Christi southward. In Mexico, it ranges south along the coast of Tamaulipas to central Veracruz. NATURAL HISTORY Th is species occurs in the deep sandy soils of coastal dunes. Inland, these soils may support a variety of veg117

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Phrynosomatidae

Keeled Earless Lizard, coastal male, Cameron County, Texas.

etative communities, ranging from grasslands, mesquite scrub, and post or live oak savannahs. As long as there are enough open areas where the lizards may forage, they may occur in all of these habitats. They do not remain in areas where brush and forest encroachment prevents sunlight from reaching the ground. Like other earless lizards, they feed primarily upon small insects, spiders, and other terrestrial arthropods. Their activity period is more extensive than that of their northern relatives, and they may be active from late February until December. In late winter and early spring, they are active at midday, but by late spring, their activity is restricted to early morning. To avoid the midday heat, they may burrow into the sand or retreat into the burrows of other lizards, mammals, or (in coastal situations) sand crabs. REPRODUCTION As in other species of the genus Holbrookia, this species breeds from April to July, may breed more than once during a single season, and produces clutches of 4–6 eggs. Gravid females develop a yellowish wash on their heads and flanks. Eggs are laid in burrows in the sand, and incubate for 45–60 days. Hatchlings are approximately 38 mm (1.5 inches) in total length. They grow fast and typically reach sexual maturity by the following spring. 118

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Keeled Earless Lizard

COMMENTS AND CONSERVATION Th is species is on the TPWD’s Black List and may not be captured for commercial purposes. It is still very common along the coast, but may have declined inland as the result of changes in rangeland conditions. Inland populations are widely scattered.

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Phrynosomatidae

Texas Horned Lizard

Phrynosoma cornutum (Harlan, 1824)

SIZE Snout-vent length may be up to 130 mm (5.2 inches), with a total length of up to 181 mm (7.2 inches). Females are larger than males. DESCRIPTION The Texas Horned Lizard is one of the state’s most distinctive lizard species. It has a proportionally small, spiny head with a blunt snout, a distinctly dorsoventrally flattened body fringed in a double row of enlarged spiny scales, and a rather short tail. The dorsum is covered with numerous small keeled scales interspersed with distinctly enlarged keeled scales, giving its back and tail a rough, spiny appearance. The back of its head is bordered with 8 enlarged spines—4 on each

Texas Horned Lizard, male, Winkler County, Texas. 120

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Texas Horned Lizard

Texas Horned Lizard, female, Presidio County, Texas.

side—with the middle pair the largest, constituting the lizard’s “horns.” There is a distinct gap between the middle pair of spines. A second pair of short spines is present over each eye, and each eye is surrounded by 2 dark lines radiating posteriorly and ventrally. The margins of the lower jaw have hardened, enlarged, and hornlike scales. The ground color is gray, tan, or yellowish, with a light (whitish or yellowish) line down the center. On either side of this light line are a series of light-bordered dark (dark gray to rich brown) spots, each of which contains a group of enlarged, keeled scales. The light borders of these dark spots may be whitish or yellowish. The whitish or yellowish ventral surface of the lizard may have a few scattered dark spots or streaks. SIMILAR SPECIES The Round-tailed Horned Lizard (Phrynosoma modestum) is smaller, lacks the fringe of scales at the edge of its abdomen, and has 4 small, equal-sized cranial horns. The Greater Short-horned Lizard (Phrynosoma hernandesi) has only extremely short cranial horns and a single row of lateral fringing scales on the abdomen. Although Texas Spiny Lizards (Sceloporus olivaceus) may be confused with horned lizards by the general public, they lack distinct cranial horns, are covered with keeled and spiny scales of equal size over their bodies, have long tails, and are not dorsoventrally flattened. 121

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Phrynosomatidae

Texas Horned Lizard, male, Dimmitt County, Texas.

DISTRIBUTION Formerly, the Texas Horned Lizard occurred in all parts of Texas except the Big Thicket of southeastern Texas and extreme northeastern Texas. Today, it has largely been extirpated east of Interstate Highways 35 and 37 except at very few localities in deep sandy soil. Outside Texas, it occurs from Kansas, extreme southwestern Missouri and northwestern Arkansas, and southeastern Colorado south to the Mexican states of San Luis Potosí and northern Veracruz. It formerly ranged as far east as northern Louisiana and currently ranges west to southeastern Arizona. NATURAL HISTORY The Texas Horned Lizard is an extreme dietary specialist. Nearly all of its diet consists of harvester ants of the genus Pogonomyrmex; virtually all the other dietary items present in fecal analysis consist of ant-sized insects most likely taken by the lizards when feeding along harvester ant trails. It has been estimated that twenty ant colonies are necessary to support a single lizard, and a feeding lizard moves from one colony to the next after consuming no more than 20 or so ants at each. Texas Horned Lizards have a variety of defenses against predators. Their flattened shape allows them to press themselves against the ground, which prevents shadows and allows their spotted patterns to blend in with the substrate. Furthermore, the large spines on the heads of the adults can be forcibly 122

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Texas Horned Lizard

Texas Horned Lizard, male, Jeff Davis County, Texas.

stabbed into the mouth of a potential predator, allowing escape. The most fascinating antipredator defense of the Texas Horned Lizard is its ability to squirt blood forcibly from the corners of its eyes. Upon being accosted by a potential predator, the tissues of the eye socket may bulge, increasing the blood pressure in the thin capillaries in the corners of the eyes. A jet of blood squirted from the eye socket can be aimed very accurately, often into the face of the predator. Usually, only a single squirt can be shot from each eye. To a human, the lizard’s blood has a salty, metallic taste but produces no deleterious effects. This blood-squirting behavior is most readily elicited by threats from dogs, coyotes, or foxes, and it has been shown to cause a taste that these species cannot tolerate. In fact, the behavior is so specific to threats from canids and felids that it is only rarely performed in response to threats from humans. These lizards are active from late February through October. They are active at midday early in the season, and as the daily temperature increases in the summer, they switch to morning and evening activity to avoid midday heat. The species occurs in arid to semiarid grasslands, savannahs, and thorn scrub. They are ground dwellers that may seek refuge in shallow scrapes dug in the shade of vegetation, in animal burrows, or under rocks. 123

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The lizards breed from spring to late summer, producing multiple clutches of 13–50 eggs in a single season (average clutch size is 25). The largest females produce the largest clutches. Hatchlings are small, approximately 30 mm (1.25 inches) in total length, and are unarmored, with only the smallest buds for horns. They grow rapidly, and may reach sexual maturity by late summer or the following spring, depending on when the eggs were laid. COMMENTS AND CONSERVATION The Texas Horned Lizard was one of the first species protected by the State of Texas. In the 1950s and 1960s it was a staple of the commercial reptile trade, and huge numbers of individuals were shipped across the country. Unfortunately, the life history of this species and its dependence upon harvester ants as a staple of its diet almost certainly doomed all of those captives to an early death. Stories of these lizards surviving for decades while entombed in the walls of Texas county courthouses are undoubtedly fanciful. The application of pesticides, resulting in the loss of harvester ant colonies from the landscape, has eliminated this species from the eastern third of Texas. Pesticide use aimed at thwarting the spread of the imported red fi re ant (Solenopsis invicta) has also caused declines and the loss of native harvester ants. To eradicate fire ants, pesticides should be directly applied to the colonies, rather than broadcast, in areas where harvester ants still persist; this precaution will help prevent the loss of harvester ants—the sole food source for the Texas Horned Lizard. To gather information on the presence, abundance, and decline of Texas Horned Lizards throughout Texas, the TPWD’s Texas Nature Trackers program has instituted a citizen science project called the Texas Horned Lizard Watch. See the Texas Parks and Wildlife website at http://www.tpwd.state.tx.us/hunt wild/wild/wildlife_diversity/texas_nature_trackers/horned _Lizard/ for more details. REPRODUCTION

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Greater Short-horned Lizard

Greater Short-horned Lizard

Phrynosoma hernandesi Girard, 1858

SIZE Snout-vent length may be up to 112 cm (4.4 inches), with a total length of up to 159 mm (6.75 inches). Females are larger than males. DESCRIPTION The Greater Short-horned Lizard has a heart-shaped head with 4 pairs of short, equal-sized occipital horns and another pair of similar-sized horns above each eye. The middle pair of horns is separated by a deep notch, giving the lizard’s head a heart shape when viewed from above. The body is dorsoventrally flattened and roughly disc shaped, almost as broad as it is long, and fringed with a single row of fringe scales. The

Greater Short-horned Lizard, male, Eddy County, New Mexico. 125

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Phrynosomatidae

Greater Short-horned Lizard, female, Lincoln County, New Mexico.

body is covered with a mix of small granular scales and large triangular-shaped keeled scales. The tail is very short. Ground color in this species is extremely variable, ranging from light tan to pinkish gray to dark brown, and many individuals have orange coloration on the head and flanks. The head is usually monochromatic or nearly so. The body is marked by paired nuchal blotches, followed by 2 or 3 wavy dark bands that may or may not be bordered with lighter color. More dark bands may appear on the tail. The intensity of these dark bands varies from individual to individual—in some specimens, the dark bands are only slightly darker than the ground color, while in others they are rather distinct. The species lacks a vertebral stripe. SIMILAR SPECIES The Texas Horned Lizard and the Round-tailed Horned Lizard are usually found at lower elevations than the Greater Short-horned Lizard. The Texas Horned Lizard can be distinguished because it has 2 large occipital horns, dark streaks radiating from its eyes, a light dorsal stripe, and a double row of fringing scales. The Round-tailed Horned Lizard has 4 equallength horns of moderate size, lacks dorsal crossbands, and lacks abdominal fringing scales. No other Texas species is likely to be confused with the Greater Short-horned Lizard. DISTRIBUTION In Texas, the Greater Short-horned Lizard is restricted to higher elevations in the Davis, Guadalupe, Cornudas, 126

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Greater Short-horned Lizard

Greater Short-horned Lizard, male, Jeff Davis County, Texas.

and Hueco Mountains in Culberson, El Paso, Hudspeth, and Jeff Davis Counties. It should be searched for at higher elevations in other Trans-Pecos mountain ranges. Outside Texas, it ranges from southern Canada in Alberta and Saskatchewan through Montana, Wyoming, Colorado, Utah, Arizona, and New Mexico. Eastward, it can be found on the western edges of the Great Plains in Nebraska and North and South Dakota. In Mexico, it occurs in the Sierra Madre Occidental in Sonora, Chihuahua, Durango, and Zacatecas. NATURAL HISTORY In Texas, this species occurs primarily at higher elevations in forests of piñon, juniper, oak, and ponderosa pine. It is typically present in open grassy and gravelly situations in the understory of these forests. The population recorded from the Hueco Mountains occurs in a high-elevation grassland. The lizard is active from March through October, and can be active at much cooler air temperatures than many other species of lizards. Individuals can be surface-active at temperatures as low as 1.5°C (35°F) if they are able to bask and elevate their body temperatures behaviorally. Like other horned lizards, this species feeds primarily on ants, but its diet includes a much larger percentage of other insects, such as beetles, crickets, plant bugs, and grasshoppers. Larger individuals, with their larger heads and jaws, may be more opportunistic than smaller ones. Like 127

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the Texas Horned Lizard, this species is capable of squirting blood from the corners of its eyes, and as in that species, this behavior is typically provoked by canids such as coyotes and foxes. REPRODUCTION The Greater Short-horned Lizard is a live bearer. The average litter size is 16, and ranges from 6 to 31. Live birth in this species is thought to be an adaptation to the colder, highelevation habitats in which the lizard occurs. A pregnant female may be better able to maintain optimum incubating temperatures within her body than by laying eggs in the ground. Newborn Greater Short-horned Lizards are about 30 mm (1.5 inches) in total length. Growth is rapid, but given the shorter growing season common at higher elevations, not all individuals will reach sexual maturity by the following spring. Some males may do so, but most females delay sexual maturity until their second spring. COMMENTS AND CONSERVATION The Greater Short-horned Lizard is considered a threatened species in Texas because of its limited distribution, being present only at the highest elevations of Trans-Pecos mountain ranges. The species may not be collected without appropriate scientific collecting permits.

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Round-tailed Horned Lizard

Round-tailed Horned Lizard

Phrynosoma modestum Girard, 1852

SIZE Snout-vent length may be up to 71 mm (2.75 inches), with a total length of up to 105 mm. The sexes are similar in size. DESCRIPTION Th is is Texas’s smallest horned lizard. The back of its head has 4 medium-length, equal-sized horns. Its dorsoventrally flattened body is round or oval when viewed from above. It lacks the row or rows of fringing abdominal scales present in other horned lizards, and its short tail is tapered and rounded rather than flattened as in other horned lizard species. It lacks the welldeveloped and prominently enlarged dorsal scales seen in other horned lizards. Its coloration closely matches its background:

Round-tailed Horned Lizard, female, Brewster County, Texas.

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Phrynosomatidae

Round-tailed Horned Lizard, male, Terrell County, Texas.

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individuals living on limestone soils are predominately whitish or gray, and those living on volcanic soils appear reddish. Irregular dark nuchal blotches are present on the neck, and similarly irregular dark blotches are on the flanks just anterior to the hind limbs. These blotches break up the lizard’s outline and provide a high degree of camouflage, allowing the species to “hide in plain sight” amid rocks and pebbles in its arid habitat. SIMILAR SPECIES Both of Texas’s other horned lizard species are significantly larger as adults, have 1 or 2 rows of lateral fringing scales on the abdomen, and have flattened tails. The Texas Horned Lizard has a pattern of spots coupled with a light line down the spine, and a greatly enlarged pair of occipital horns. The Greater Short-horned Lizard has a pattern of wavy crossbars and much shorter horns, the occipital pair being separated by a deep notch between them. From a distance, the Roundtailed Horned Lizard may be confused with the Greater Earless Lizard, since both are approximately the same size and are often the same color, but the earless lizard lacks the horns of the horned lizard and has a much longer and slimmer body. DISTRIBUTION The Round-tailed Horned Lizard occurs in the western third of the state, in the Caprock canyons near Amarillo south through the Midland-Odessa region to Val Verde County westward through the Trans-Pecos. Isolated records in Baylor County in the Rolling Plains and in Webb, Jim Hogg,

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Round-tailed Horned Lizard

and Zapata Counties in South Texas are known. The species occurs in the extreme western end of Oklahoma’s panhandle and in the Pecos and Rio Grande Valleys of New Mexico westward into southeastern Arizona. In Mexico, its range extends south to Zacatecas and San Luis Potosí. NATURAL HISTORY Th is species occurs primarily in arid and semiarid areas on rocky or gravelly substrates. It prefers open areas where vegetation is sparse. Ants make up a significant proportion of its diet, and while it may feed on harvester ants occasionally, ants of smaller species are dietary staples. With their small horns and small size, these lizards are much less capable than Texas Horned Lizards of defending themselves, and so rely primarily on camouflage in order to avoid predators. With their countershaded bodies and ability to arch their backs in a hunched posture, they are extraordinarily capable of mimicking rocks and small pebbles and can disappear in an instant on gravelly substrates. Unlike Texas Horned Lizards and Greater Short-horned Lizards, they do not seem capable of squirting blood from their eyes. Their activity period ranges from March through October or November. During the spring and fall, they can be active all day, while during the summer they are primarily active in the morning or late afternoon. REPRODUCTION Th is small species breeds in May through July, and lays clutches of 6–19 eggs. Hatchlings are similarly sized to those of other horned lizard species, approximately 30 mm

Round-tailed Horned Lizard, male, Brewster County, Texas.

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Round-tailed Horned Lizard, female, Brewster County, Texas.

Round-tailed Horned Lizard, male, Brewster County, Texas.

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(1.25 inches) in total length. They grow fast and can reach sexual maturity by the spring after hatching. COMMENTS AND CONSERVATION Th is species is on TPWD’s Black List and may not be collected for commercial purposes. Of the Texas horned lizard species, the habits of the Round-tailed Horned Lizard are the most poorly known and least studied. They can be locally abundant, particularly on gravelly slopes in the Chihuahuan Desert.

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Common Side-blotched Lizard

Common Sideblotched Lizard

Uta stansburiana Baird and Girard, 1852

SIZE Snout-vent length may be up to 54 mm (2.2 inches), with a total length of up to 137 mm (5.4 inches). Males and females are approximately the same size. DESCRIPTION Th is is a small, slim lizard with a distinctive lightbordered black spot just behind the armpit. The body is covered in small granular scales over most of its surface, coupled with several rows of larger keeled scales along the spine. It has a fold of skin beneath the neck. The overall pattern is both striped and spotted; 2 stripes begin on each side of the head and extend posteriorly from the eyes and lips. Males exhibit a profusion of spots: whitish ones on the forebody and sides, shading to

Common Side-blotched Lizard, male, Winkler County, Texas.

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Phrynosomatidae

Common Side-blotched Lizard, female, Presidio County, Texas.

blue ones on the back, hips, and tail. The throat in males may be washed with a bluish tint (which may be orange or yellowish in populations west of Texas). Striping in males is largely confi ned to the head and neck. In females, the stripes are more prominent than in males, extending from the head and neck toward the hips. Overall, the females are a rich brown in color, with yellowish or whitish stripes. SIMILAR SPECIES While earless lizards (Holbrookia and Cophosaurus) may appear similar, they lack external ear openings and have 2 gular folds. If spots are present on their sides, earless lizards have 2 lateral spots rather than 1 spot, as is seen in the Common Side-blotched Lizard. Ornate Tree Lizards (Urosaurus ornatus) are similar in size and shape, but lack the lateral spot and the pattern of light stripes and spots. Spiny lizards (Sceloporus) may be similar in size, but lack the lateral side spot and have bodies covered with large keeled scales, each with a distinct point. DISTRIBUTION Th is species occurs primarily in southwestern Texas, from the canyons of the Caprock near Amarillo, east along the Red River to Hardeman County and south through Sterling County to Val Verde County west through the TransPecos. Outside Texas, it is found in extreme southwestern Oklahoma, southern New Mexico (primarily in the Pecos River and 13 4

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Rio Grande Valleys), southern and western Arizona, and north to the Four Corners region of the Colorado Plateau, where New Mexico, Arizona, Colorado, and Utah come together. It occurs through the Great Basin across Nevada, southwestern Idaho, western Oregon, and north to southeastern Washington. It occurs throughout southwestern California and north to the San Francisco Bay area. In Mexico, it ranges throughout the Baja California Peninsula, most of Sonora, eastern Chihuahua, eastern Durango, western Coahuila, and to extreme northern Zacatecas. NATURAL HISTORY The Common Side-blotched Lizard is primarily active in Texas from late February to November. It may also be active on sunny winter days, particularly when several such days coincide. In spring and fall, it may be active all day, while in summer its activity patterns are distinctly bimodal, with activity confined to the morning and late evening. The Common Side-blotched Lizard is a sit-and-wait predator, feeding primarily on small insects and arachnids. For defense against predators, the Common Side-blotched Lizard rarely strays far from the security of bushes or rocks, into or under which it may dash to safety. It occurs primarily in desert flats or lower mountain slopes where bare ground is interspersed with bushes or large rocks. In many areas, the Common Side-blotched Lizard is the most abundant lizard.

Common Side-blotched Lizard, male, Ward County, Texas. 135

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Breeding and courtship occur throughout the activity season, with 1–7 clutches of 1–8 eggs laid in a single season (March through August). Incubation takes 60–80 days, depending upon the temperatures present in the underground chamber in which the eggs are laid. Hatchlings are approximately 59 mm (2.25 inches) in total length. They grow rapidly, reaching adult size within 3 or 4 months, although reproductive maturity is not reached until the following spring. This species’ life span may be as long as 4 years, but most individuals survive for only a single reproductive season. COMMENTS AND CONSERVATION Th is often-abundant species is on the TPWD’s White List and so may be collected for commercial purposes with the appropriate permits. Some authorities consider Texas’s populations to be a distinct species in its own right, the Eastern Side-blotched Lizard (Uta stejnegeri). But this taxonomic designation is not widely accepted, and the evidence for the differentiation is based primarily on a lack of records between eastern populations in Texas and New Mexico and populations to the west in Arizona. REPRODUCTION

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Ornate Tree Lizard

Ornate Tree Lizard

Urosaurus ornatus (Baird and Girard, 1852)

SIZE Snout-vent length may be up to 51 cm (2 inches), with a total length of up to 137 mm (5.4 inches). Males and females are approximately the same size. DESCRIPTION The Ornate Tree Lizard is a slim arboreal or saxicolous (rock-dwelling) lizard with a long tail. The body is covered by a mixture of small granular scales interspersed with irregular rows of enlarged keeled scales on the middle of the back. It has a distinct ventral gular fold where the neck joins the body, and 2 lateral folds extending from the forelimbs to the hind limbs. The body is typically grayish or brownish, and the predominant

Ornate Tree Lizard, male, Brewster County, Texas. 137

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Phrynosomatidae

Ornate Tree Lizard, female, Travis County, Texas.

coloration loosely matches the underlying substrate—grayish on limestone substrates, brownish on volcanic rocks. An irregular pattern of wavy black lines cross the dorsum from the back of the head to the tail. These dark markings may be outlined with a lighter color in some specimens or populations. A distinct white line is present on the lips. In some individuals, the tail may be brownish. When cold or involved in a territorial dispute, it may darken and appear almost black. The throat of males may be blue, green, orange, or yellow; belly patches are blue. Females typically have faint yellowish throats and white or faintly bluish bellies. SIMILAR SPECIES The Common Side-blotched Lizard (Uta stansburiana) typically has a distinct lateral spot and a pattern of lines and light spots; it is also typically found terrestrially, while the Ornate Tree Lizard is a climbing species, inhabiting trees, large rocks or cliffs. The Canyon Lizard (Sceloporus merriami) has only a partial gular fold, larger keeled dorsal scales, and a ventral pattern of pinkish or orange patches outlined in blue. Other small spiny lizard species (genus Sceloporus) are larger and differ in scalation in much the same way as does the Canyon Lizard. DISTRIBUTION The Ornate Tree Lizard occurs throughout the Edwards Plateau west through the Trans-Pecos. Populations are 138

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Ornate Tree Lizard

present also along the Rio Grande south to near its mouth at the Gulf of Mexico. It occurs west to the Colorado River Valley in eastern California and north into the Colorado Plateau of eastern Utah and western Colorado. In New Mexico, it occurs chiefly west of the Rio Grande Valley. In Mexico, it ranges through Sonora into Sinaloa on the Pacific Coast, and throughout most of Chihuahua, with isolated records in central Coahuila (although it likely is more widely distributed in that state). NATURAL HISTORY The Ornate Tree Lizard is a distinctly arboreal or saxicolous species and may inhabit trees or rocky areas equally. Highly cryptic, it may be quite difficult to see when it is resting motionless against a tree branch or on a boulder. The species may escape predation by climbing out of a predator’s reach or by retreating into hollows in a tree trunk or into rock crevices. It is an ambush predator that feeds primarily on small insects and arachnids. It is active primarily from late February until November but may also be active during the winter when warmer weather permits. On the Edwards Plateau, it occurs in oak and juniper woodlands, using trees as well as rock outcrops, and is perhaps most common in such sites. Westward through the Stockton Plateau and the Trans-Pecos, it is common in canyons and on mountain slopes, using rocky cliffs where trees are absent, and both trees and boulders at higher elevations. The

Ornate Tree Lizard, male in territorial display, Brewster County, Texas. 13 9

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Phrynosomatidae

lizards may colonize the walls of buildings, fences, and other structures. REPRODUCTION Breeding and courtship may occur throughout most of this lizard’s active season. A female may lay several clutches of 2–16 eggs. Eggs are laid in small chambers under rocks or in tree hollows. Hatchlings are about 40 mm (1.25 inches) in total length. They grow fast and may reach sexual maturity by the following spring. COMMENTS AND CONSERVATION Th is common species is on the TPWD’s White List and so may be collected commercially with the appropriate permits.

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Rose-bellied Lizard

Rose-bellied Lizard

Sceloporus variabilis Wiegmann, 1834

SIZE Snout-vent length may be up to 57 mm (2.2 inches), with a total length of up to 140 mm (5.5 inches). Males are larger than females. DESCRIPTION Th is is a distinctly striped spiny lizard, with the stripes being more prominent in males. There are 2 light dorsolateral stripes running from the sides of the head to the base of the tail. The stripes range in color from tan or whitish to yellowish and are 1 or 2 scales wide. The ground color between the stripes is occupied by a series of paired dark spots, 9 or 10 in number, which are bordered posteriorly by light coloration.

Rose-bellied Lizard, male, Bexar County, Texas. 141

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Phrynosomatidae

Rose-bellied Lizard, venter, male, Dimmitt County, Texas.

Rose-bellied Lizard, female, Hidalgo County, Texas.

These spots are more prominent in females than in males— in some males they may be obscured altogether. The sides are brownish, often with a reddish cast in males. A black spot or bar on each side extends from just behind to the forelimb up to the light dorsolateral stripe. Th is dark bar is bordered anteriorly by a light bar. In males, the paired ventral belly patches are a bright rosy pink, bordered midventrally by a thin line of blue. The belly 14 2

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Rose-bellied Lizard

patches are separated by a thin strip of the whitish ventral coloration that occurs on the remainder of the belly. SIMILAR SPECIES No other Texas Sceloporus has a postfemoral dermal pocket, although this feature is difficult to observe in the field. Where their ranges overlap, the members of the Eastern Fence Lizard complex (Sceloporus undulatus) lack light dorsolateral stripes. Male Eastern Fence Lizards have blue rather than pink belly patches, and both sexes of the species have distinct dorsal crossbars. The Mesquite Lizard (Sceloporus grammicus) lacks light dorsolateral stripes, is distinctly more arboreal in its habitats, has blue rather than pink belly patches (males), and has distinct dorsal crossbars (both sexes, although males often appear black while basking). The Texas Spiny Lizard (Sceloporus olivaceus) is much larger and has fewer and obviously larger dorsal scales. DISTRIBUTION In Texas, the Rose-bellied Lizard occurs from Kinney, Bandera, and Hays Counties south throughout the South Texas brush country. It ranges south along the Gulf Coast of Mexico to Costa Rica. It also crosses the Isthmus of Tehuantepec to the Pacific Coast in southern Mexico and ranges on the Pacific Coast south to Guatemala. NATURAL HISTORY In Texas, this species occurs primarily along major rivers, although it can be found elsewhere. It prefers ar-

Rose-bellied Lizard, male, Bexar County, Texas. 14 3

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Rose-bellied Lizard, hatchling, Bexar County, Texas.

eas with large trees, including live oaks, Texas ebony, and hackberries. Although an agile climber, it has distinctly terrestrial tendencies and is among the most terrestrial members of the genus Sceloporus. It feeds primarily on insects; grasshoppers, butterflies (both adults and caterpillars), spiders, fl ies, and beetles make up most of its diet. Like other species in Sceloporus, this one is primarily a sit-and-wait ambush predator, sitting on a perch from which it can survey its surroundings and then dashing out to grab a potential prey item. It may also take prey as “targets of opportunity” while moving through its habitat. It may frequently be observed basking in the early morning on rocks, tree limbs, and patches of open ground. During the midday heat, Rose-bellied Lizards typically retreat to dense shade, where they may remain active throughout the day. REPRODUCTION Reproductive activity may occur throughout the active season of this species, which begins in March and may continue into late November. Females lay several clutches of 1– 6 eggs annually, typically in a shallow burrow dug by the female for the purpose of egg-laying. Incubation of the eggs takes 60– 75 days depending upon temperature. The hatchlings are small, usually less than 25 mm (1 inch) from snout to vent. The lizards grow rapidly and may reach sexual maturity the following summer. 14 4

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COMMENTS AND CONSERVATION The Rose-bellied Lizard occurs in scattered populations from the Balcones Escarpment south throughout South Texas, primarily along streams and rivers but not restricted to that habitat. Abundance varies tremendously throughout its large range. In some areas it is quite rare, and a herpetologist would be lucky to observe 1 or 2 specimens a year. In other areas of seemingly similar habitat, it can be the most abundant lizard species, outnumbering such notably common lizards as the ubiquitous Texas Spotted Whiptail (Aspidoscelis gularis). This species is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Canyon Lizard

Sceloporus merriami Stejneger, 1904

SIZE Snout-vent length may be up to 62 mm (2.4 inches), with a total length of up to 159 mm (6.25 inches). Males are slightly larger than females. DESCRIPTION The Canyon Lizard is a rather plain lizard inhabiting rocky canyons and cliffs. Its overall coloration ranges from pale gray or buff to a rather dark tan or reddish brown, typically matching or closely matching the rocks among which it lives. The most prominent dorsal marking is a black vertical bar on both sides of the neck. Rather faint, paired dark spots may be present down the back in some specimens, and the tail may

Canyon Lizard, male, Terrell County, Texas. 14 6

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Canyon Lizard

Canyon Lizard, venter, male, Terrell County, Texas.

Canyon Lizard, female, Terrell County, Texas.

be faintly banded. The dark dorsal markings are typically more distinct in females than males. Mature males have a pattern of light spots over most of their flanks and backs. Males have paired belly patches that are orange or pinkish bordered midventrally and posteriorly by blue. The patches are typically well separated by white. Males may also have a poorly defined blue throat patch or blue bars. Some males show blue markings cor147

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Canyon Lizard, male, Brewster County, Texas.

responding to the faint dorsal rings on the undersides of their tails. Females may have faint orange patches on their bellies. Juveniles are similar in coloration to adults, but are often paler and even more faintly marked. Individuals of all sexes and ages have an incomplete gular fold on their throats; the folds are distinct on the lateral sides of the necks but interrupted midventrally. SIMILAR SPECIES The Canyon Lizard is most similar to the cooccurring Ornate Tree Lizard (Urosaurus ornatus). The Ornate Tree Lizard differs in having a complete gular fold, mostly smaller dorsal scales with enlarged middorsal scale rows, and (in males) solid blue belly patches rather than orange or pinkish patches bordered in blue. The Eastern Fence Lizard (Sceloporus undulatus complex) is larger as an adult, has larger dorsal scales, has a faintly striped pattern, and (in males) has blackbordered blue belly patches. Other co-occurring Sceloporus species are much larger as adults and have much larger scales at all ages. The Rose-bellied Lizard (Sceloporus variabilis) is the only other Sceloporus species that may have pink belly patches, but its range is not known to overlap with that of the Canyon Lizard, and the 2 species occupy very different habitats. DISTRIBUTION Th is species is most abundant in the counties bordering the Rio Grande and the Pecos River, including Presidio, Brewster, Pecos, Crockett, Terrell, and Val Verde. Records 14 8

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also exist for Edwards, Schleicher, Jeff Davis, Reeves, Ward, and Winkler Counties. In Mexico, it is known from scattered localities in northern Chihuahua and Coahuila but is probably rather widespread in mountainous regions of those states. NATURAL HISTORY The Canyon Lizard is aptly named, since it shows a distinct preference for rocky canyons and rock faces, both naturally occurring and man-made. These lizards are notably abundant on rocky road cuts where hillsides were blasted back during road construction. The Canyon Lizard occurs primarily in Chihuahuan Desert regions, from lower desert canyons up to the lower slopes of mountains. The Canyon Lizard is a sit-and-wait predator that feeds primarily on spiders and small insects such as grasshoppers, crickets, ants, and beetles. In general, the species is active from March through October, but this is variable across the wide range of elevations it inhabits. Lowelevation populations are active earlier in the year than those at higher elevations. During midsummer, low-elevation populations typically must retreat to the shelter of crevices during midday to avoid the heat of the summer sun, whereas high-elevation populations are typically active throughout the day. Interestingly, mid-elevation populations show the fastest growth rates, since mid-elevation conditions apparently provide the lizards with the “best of both worlds.”

Canyon Lizard, male, Presidio County, Texas. 14 9

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Breeding occurs primarily from May through August. Males frequently employ push-up displays that include extending their small dewlaps as well as dorsolaterally flattening their bodies to fully expose their belly patches. These displays serve to attract females and to warn other males away from their territories. Females lay 1–2 clutches of 4 eggs (on average) a year. Hatchlings are about 50 mm (2 inches) in total length. Most males reach reproductive maturity in their second summer, but some females may not reach reproductive size until their third summer. COMMENTS AND CONSERVATION Th is species is often quite abundant in appropriate habitats and may be found commonly on road cuts at lower elevations throughout its range. Despite its local abundance, it is on the TPWD’s Black List and so may not be collected for commercial purposes. REPRODUCTION

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Mesquite Lizard

Mesquite Lizard

Sceloporus grammicus Wiegmann, 1828

SIZE Snout-vent length may be up to 73 mm (2.9 inches), with a total length of up to 175 mm (6.9 inches). Males are larger than females. DESCRIPTION Th is is a small spiny lizard. When active, males appear especially dark colored, almost black. Upon capture, the dark coloration fades to reveal the underlying pattern of wavy

Mesquite Lizard, male, Hidalgo County, Texas.

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Mesquite Lizard, venter, male, Nuevo Leon, Mexico.

Mesquite Lizard, female, Hidalgo County, Texas.

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dark crossbars on a brownish or dark gray ground color. Females are usually light gray with widely spaced thin crescents in 2 rows along their back. The curved part of the crescent points toward the head. Both sexes have a series of bars on their front legs. Males in Texas have yellow, orange, or white throats and paired patches on their bellies that are pale blue, bordered with black in the center. Belly patches sometimes merge together near the anterior end of the patches. The scales on the nape of

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the neck are distinctly and abruptly larger than the scales on the sides of the neck, a trait that (in hand) can be used to distinguish this species from other co-occurring spiny lizards. SIMILAR SPECIES In hand, all other members of the genus Sceloporus that occur with the Mesquite Lizard have similarly sized scales on the sides and nape of the neck. The Rose-bellied Lizard (Sceloporus variabilis) has a pair of pale dorsolateral lines extending the length of the body, and males have a rosy-colored belly patch. Members of the Eastern Fence Lizard complex (Sceloporus undulatus) have larger and fewer dorsal scales and do not have dark bars on their front legs. Texas Spiny Lizards (Sceloporus olivaceus) are much larger, and have much larger dorsal scales. Ornate Tree Lizards (Urosaurus ornatus) have mostly smaller dorsal scales, with an enlarged row of scales down the middle of their back. DISTRIBUTION Mesquite Lizards reach the northeastern edge of their distribution in the thickets of the Rio Grande Valley. They are known from Cameron, Hidalgo, Jim Hogg, Starr, and Zapata Counties. An introduced population is known from the campus of Texas A&M University–Kingsville in Kleberg County. They are found throughout much of Mexico, especially in the major mountain ranges and extending south to Guerrero. NATURAL HISTORY As their common name suggests, Mesquite Lizards are frequently found in mesquite thickets along the Rio

Mesquite Lizard, male, Nuevo León, Mexico.

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Grande and its associated resacas and ditches. They are primarily arboreal and shy. Uncommon in Texas, they occur sympatrically with the similarly sized Rose-bellied Lizards, which are much more abundant. Like others of their genus, they are sitand-wait ambushers that eat mostly small insects and spiders. REPRODUCTION Little is known about their reproduction in Texas, but like similar lizards in South Texas, they breed in April and May. Females give birth to live young in June and July. They likely reach sexual maturity in their first spring. COMMENTS AND CONSERVATION Not much is known about the populations of the Mesquite Lizard in Texas, where they are at the extreme edge of their distribution. Furthermore, the lowland riparian habitats used by Texas populations are anomalous when compared to those used by the species throughout the bulk of its distribution—primarily montane pine-oak forests in the highlands of Mexico. Although uncommon, Texas populations seem to be stable and are afforded some protection by being on the TPWD’s Black List. The greatest threat to this species in Texas is the elimination of riparian groves along the Rio Grande.

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Dunes Sagebrush Lizard

Dunes Sagebrush Lizard

Sceloporus arenicolus Degenhardt and Jones, 1972

SIZE Snout-vent length may be up to 70 mm (2.75 inches), with a total length of up to 152 mm (6 inches). Males are larger than females. DESCRIPTION Th is is a small nondescript lizard. Its dorsal color matches that of the sand on which it lives, which varies from a light tan to reddish tan. It has dorsolateral grayish stripes that extend from just behind the head to the pelvic region. Males have paired blue patches on their bellies but do not have throat patches. Females have an immaculate white to yellowish venter. During the breeding season, females develop patches of orange along the sides of their heads, bodies, and tails. They have 41–52 scale rows around the midbody, granu-

Dunes Sagebrush Lizard, male, Andrews County, Texas.

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Dunes Sagebrush Lizard, female, Andrews County, Texas.

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lar scales on the back of their thighs, and more than 9 scale rows separating the femoral pores. SIMILAR SPECIES Populations of the Eastern Fence Lizard (Sceloporus undulatus complex) found in habitats similar to those used by this species are very difficult to distinguish from the Dunes Sagebrush Lizard unless one has the lizard in hand. Members of the Sceloporus undulatus complex can be identified by having fewer than 7 scale rows between the femoral pores on the innermost part of the leg. Also, Eastern Fence Lizards have pointed scales on the back of the thighs. DISTRIBUTION Th is species has one of the smallest distributions of any lizard in North America. It is restricted to the Mescalero and Monahans Sandhills regions of southeastern New Mexico and western Texas. In Texas, it is known only from Gaines, Andrews, Winker, Ward, and Crane Counties. Extensive, rangewide surveys have been conducted over the last 10 years, and no individuals have been reported from Crane County during those surveys. REPRODUCTION Breeding occurs from May through July. Clutches of 3–6 eggs are laid in underground refugia near the interface between dry and moist sand, approximately 18 cm (7.1 in.) beneath the sand surface. Females may lay 1 or 2 clutches of eggs annually. Hatchlings measure about 44 mm (1.7 inches) in total length and emerge in late July and August. They grow rapidly,

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with males and most females reaching sexual maturity by the following summer. NATURAL HISTORY The Dunes Sagebrush Lizard is a habitat specialist. It is restricted to sand dunes that are stabilized by Havard shin oak (Quercus havardii) and have open depressions called blowouts. The lizards specifically use the interface between the oak and the open sand. They are ambush predators that feed on small insects and spiders. They are generally active from late March to October. Most active as the temperatures are warming in the morning, they have a smaller activity peak in the late afternoon after temperatures begin to cool. Males are territorial, and most have small bite marks indicating that territories are maintained by fighting. Females also commonly have bite marks, which could indicate aggressive courtship behavior or territoriality between females. COMMENTS AND CONSERVATION These lizards have only recently been listed as endangered in Texas. A conservation plan is now in place for them. Populations have been shown to be susceptible to fragmentation of their habitat. Fragmentation usually occurs through the construction of caliche roads and well pads for oil and gas drilling. Population declines have been attributed as well to the application of the herbicide tebuthiuron, a broadspectrum herbicide used to kill Havard shin oaks. The removal of the oak can destabilize the dunes.

Dunes Sagebrush Lizard, hatchling, Andrews County, Texas. Photo by Terry L. Hibbitts.

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Eastern Fence Lizard complex

Sceloporus undulatus complex (Bosc and Daudin, 1801)

SIZE Snout-vent length may be up to 75 mm (3 inches), with a total length of up to 180 mm (7 inches). Males and females are similar in size. DESCRIPTION Members of the Eastern Fence Lizard complex display a wide range of colors and patterns across their broad range. Individuals in the eastern portion of the state, as well as in wooded regions in Central and South Texas, display patterns consisting primarily of irregular wavy dorsal crossbars and faintly indicated dark lateral stripes extending from forelimb to hind limb. Males in these populations are typically more obscurely marked than females, particularly in older individuals. Populations on the prairies and southwestern deserts may be marked with light dorsolateral stripes above the dark lateral ones, with the dark crossbars being faint or confined to the dor-

Eastern Fence Lizard, male, Jasper County, Texas.

Eastern Fence Lizard, male, Jasper County, Texas.

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Eastern Fence Lizard, female, Jasper County, Texas.

Eastern Fence Lizard, male, Wilson County, Texas.

Eastern Fence Lizard, male, Edwards County, Texas.

sum between the light stripes. Some populations, particularly those on the Monahans Sandhills, may be faintly marked and appear nearly patternless. Where prairies or deserts meet woodlands, individuals may show patterns intermediate between those described above. Males have 2 black-bordered blue ventral patches, typically separated by light ventral coloration. The blue gular patches are also black bordered and widely separated. 159

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Some individuals may show red coloration under their chins and on the lower portion of their jaws. Juveniles are patterned like adults, but are more faintly marked. SIMILAR SPECIES Although adult Texas Spiny Lizards (Sceloporus olivaceus) reach considerably larger sizes, juveniles of that species represent the greatest identification challenge in distinguishing them from Eastern Fence Lizards. The 2 species are often very similar in pattern, having similar patterns of faint, light dorsolateral lines combined with irregular wavy dark bars across the backs. But Texas Spiny Lizards of all ages have larger, more prominent dorsal scales that number 33 or fewer (counted from back of the head to the base of the tail), while the members of the Eastern Fence Lizard complex have 35 or more. Eastern Fence Lizard populations in the Monahans Sandhills region that co-occur alongside the Dunes Sagebrush Lizard (Sceloporus arenicolus) may be confusingly similar to the untrained observer. Dunes Sagebrush Lizards have more than 9 scales between the inner edges of the femoral pore series. Furthermore, Dunes Sagebrush Lizards lack pointed scales on the rear margins of the thighs, which are present in Eastern Fence Lizards. DISTRIBUTION The Eastern Fence Lizard complex occurs statewide. Beyond Texas, members of this species complex range from southern New York through Pennsylvania down the Ohio River Valley, across Missouri onto the Great Plains north to South Dakota and southeastern Wyoming and west to Utah and Arizona. In the South, it ranges from the northern half of the Florida peninsula west across the Gulf Coast to Louisiana and Texas, being missing only from the Mississippi River Delta. It occurs throughout New Mexico and the northern two-thirds of Arizona. In Mexico, it ranges through extreme northwestern Tamaulipas, northern Nuevo Leon, all of Coahuila, the eastern two-thirds of Chihuahua, the eastern half of Durango, and northern Zacatecas, barely reaching San Luis Potosí. NATURAL HISTORY The Eastern Fence Lizard is primarily surfaceactive in Texas from March through October. Individuals may occasionally be observed throughout the year, emerging to bask during periods of warmer weather even during midwinter. The species is an opportunistic insectivore and primarily employs a sit-and-wait strategy, occupying elevated perches from which it can survey its surroundings. Documented prey items in16 0

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Eastern Fence Lizard, male, Fisher County, Texas.

Eastern Fence Lizard, venter, male, Fisher County, Texas.

Eastern Fence Lizard, male, Chaves County, New Mexico.

clude centipedes, spiders, grasshoppers, termites, beetles, fl ies, and ants. Since the species occurs almost statewide, it also occupies a wide range of habitats, from the Piney Woods in East Texas through the High Plains of the Panhandle and live oak mottes of the South Texas coastal plains through the deserts of the Trans-Pecos. 161

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Eastern Fence Lizard, male, Otero County, New Mexico.

Eastern Fence Lizard, female, Val Verde County, Texas.

Reproduction begins in April or May and extends throughout the active season. Females may lay 1–3 clutches of 5– 6 eggs (on average) a year. The eggs are typically laid in a shallow burrow dug by the female for the purpose of egg laying. The hatchlings are 50 mm (2 inches) in total length. They begin to appear during midsummer and may continue to emerge from eggs until October. Males are territorial and advertise territo-

REPRODUCTION

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rial possession through push-up displays in which they exhibit their blue ventral and gular patches to prospective competitors as well as to prospective mates. COMMENTS AND CONSERVATION Recent research has made it clear that the widespread group of lizards formerly regarded as a single, wide-ranging species under the name Sceloporus undulatus represents a species complex consisting of 3 or 4 distinct species within the United States and possibly more in Mexico. Unfortunately, very little has been done to accurately delineate species boundaries or morphological distinctions between the newly recognized species. Until these matters are addressed, we feel it best to continue to regard these lizards as members of the Sceloporus undulatus complex rather than to recognize new species that cannot be differentiated by morphology or geography. Texas populations apparently belong to 1 or 2 distinct species: the Prairie Lizard (Sceloporus consobrinus) occupies most of Texas exclusive of the Trans-Pecos, while the Southwestern Fence Lizard (Sceloporus cowlesi) occupies the Trans-Pecos. Although the mapped ranges of these 2 named species approach each other in a broad band near the Pecos River, the precise nature of how the ranges of these 2 species meet or overlap is not known. Even within the purported ranges of these 2 species, a tremendous amount of morphological variation is present, pos-

Eastern Fence Lizard, hatchling, Brazos County, Texas. 16 3

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sibly reflecting adaptations to local environmental conditions. The high degree of intraspecies variation has made it complicated to identify characteristics that may be used to distinguish these 2 species. At the time of this writing, no characteristics have yet been described that would allow the 2 species to be distinguished from each other where their ranges come into contact. The members of the Eastern Fence Lizard complex are on the TPWD’s White List (as Sceloporus undulatus) and may be collected for commercial purposes. Although these lizards may make suitable captives for experienced keepers who are able to provide ample food supplies, vitamin supplementation, and ultraviolet light, most of these lizards that enter the commercial trade undoubtedly do so as “feeder lizards”—a food source for lizard-eating snakes.

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Texas Spiny Lizard

Texas Spiny Lizard

Sceloporus olivaceus Smith, 1934

SIZE Snout-vent length may be up to 121 mm (4.75 inches), with a total length of up to 279 mm (11 inches). Females are larger than males. DESCRIPTION The Texas Spiny Lizard is a large tree-dwelling lizard whose coloration closely matches the trees upon which it resides. Its body is covered with particularly large, keeled, and pointed scales, numbering 33 or fewer when counted from the back of the head to the base of the tail. Females and juveniles are grayish brown and distinctly crossbanded with wavy black transverse lines across the back and on the forearms. The center of the back is darker than the sides, and the light areas on

Texas Spiny Lizard, male, Kinney County, Texas.

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Texas Spiny Lizard, venter, male, Kinney County, Texas.

Texas Spiny Lizard, female, Val Verde County, Texas.

the sides of the back may align into faint dorsolateral stripes. An irregular dark lateral stripe may be present on the flanks. In some individuals, there is a yellowish or olive wash on the lower flanks behind the forearm. Rusty markings may be present at the nape of the neck. Males are browner, less distinctly crossbanded, and more distinctly striped than females and juveniles; on males, dorsal crossbars are only faintly indicated, and 166

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the light dorsolateral and dark lateral stripes are well marked. The blue belly and throat patches typical of other Sceloporus males are small and faintly marked in this species. Hatchlings are more distinctly crossbanded than adults. SIMILAR SPECIES The geographic range of the Desert Spiny Lizard (Sceloporus magister) overlaps very slightly with that of the Texas Spiny Lizard. Adult Desert Spiny Lizards lack light dorsolateral stripes and wavy crossbars on the back, are a richer brownish color, and have a distinctive black wedge on the sides of their throats. Male Desert Spiny Lizards have extensive blue ventral patches quite unlike the vestigial ventral patches on male Texas Spiny Lizards. Crevice Spiny Lizards (Sceloporus poinsetti) and Blue Spiny Lizards (Sceloporus cyanogenys) have distinctive nuchal collars. Although adult Texas Spiny Lizards are much larger than Eastern Fence Lizards (Sceloporus undulatus complex), Mesquite Lizards (Sceloporus grammicus), and Rosebellied Lizards (Sceloporus variabilis), juveniles of Texas Spiny Lizards may be confused with members of these species. Texas Spiny Lizards can be readily differentiated from these other species in hand by counting the number of dorsal scales between the nape of the neck and base of the tail—in Texas Spiny Lizards, these number 33 or fewer, while in the smaller species they number 35 or more. Further, a juvenile Texas Spiny Lizard typically appears much “ganglier” or more “immature” than juveniles of similar species—similar to the appearance of a young teenage human or a puppy three-quarters grown. DISTRIBUTION The Texas Spiny Lizard occupies most of the central swath of the state, from the Lower Rio Grande Valley to the Red River. It ranges west to Brewster and Lubbock Counties and east to Gregg and Harris Counties. In Mexico, it ranges south into northeastern Coahuila, the northern two-thirds of Nuevo Leon, and most of Tamaulipas. NATURAL HISTORY The Texas Spiny Lizard is a distinctly arboreal species that spends most of its life in trees. For such a large lizard, it can be rather inconspicuous. Shy and wary, it typically retreats to the opposite side of a tree trunk in the presence of a potential predator (or human observer). In areas of high population densities, almost every large tree may be occupied by an adult Texas Spiny Lizard. It prefers larger tree species such as live oaks, post oaks, pecans, hackberries, and elms, but may 167

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Texas Spiny Lizard, female, Bexar County, Texas.

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be found on brushy trees such as mesquite and can be seen on man-made structures such as barns and fence posts, especially when brush provides cover at the base of these objects. Males are territorial, typically defending a single tree from encroachment by other males. They may be surface-active beginning in early March through the onset of colder weather in late October or November. During the winter, individuals may occasionally be seen basking on warm days, and they may be regularly found under cover objects such as boards or sheet metal. In the southwestern portion of its range, where large trees are mostly absent, Texas Spiny Lizards may occupy boulders, canyon walls, or concrete road culverts. Food is primarily insects, including cicadas, crickets, grasshoppers, ants, fl ies, butterflies, and caterpillars. REPRODUCTION The Texas Spiny Lizard is a prolific species that is reproductively active throughout the warm months of the year. Females may lay up to 4 clutches annually, and the size of these clutches can be truly impressive, numbering as many as 19–

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Texas Spiny Lizard, hatchling, Kinney County, Texas.

30  eggs each. These eggs are typically laid in shallow burrows constructed by females for the purpose of oviposition. Eggs incubate for 45–60 days, depending on incubation temperatures. Hatchlings are small, about 65 mm (2.5 inches) in total length. Males may reach reproductive size in their second summer, while females typically take 2 years to reach sexual maturity. COMMENTS AND CONSERVATION It is likely that the Texas Spiny Lizard has increased in range and abundance in Texas as a result of human-caused habitat alteration, since this species favors brushy and wooded country over grasslands. With the conversion of South Texas grasslands into thorn-scrub habitats, brushy encroachment on the Blackland Prairies, the invasion of mesquite into the Rolling Plains, and increases in brushy habitats on the Edwards Plateau, this species has proliferated. It remains common in urban and suburban settings where ample trees remain. Although abundant, this species is protected from commercial collection and is on the TPWD’s Black List.

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Desert Spiny Lizard

Sceloporus magister Hallowell, 1854

SIZE Snout-vent length may be up to 140 mm (5.5 inches), with a total length of up to 330 mm (13 inches). Males are larger than females. DESCRIPTION The Desert Spiny Lizard is powerfully built, with a large head and a “bulldog” shape. It is a large bronze-brown lizard with a double row of dark spots down the center of the back. In males, the spots may be purplish or (more commonly) only faintly indicated. In females and juveniles, the paired dorsal spots are black and more distinctly marked. The flanks are darker than the back and marked with scattered yellow scales. A black wedge on the sides of the neck extends from the throat

Desert Spiny Lizard, male, Brewster County, Texas. 170

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Desert Spiny Lizard

Desert Spiny Lizard, female, Graham County, Arizona.

up to about the level of the eye. In males, the throat is a bright greenish blue with darker streaks; the paired belly patches typical of the genus merge along the midline. The patches are a bright greenish blue with dark streaks and faintly indicated black borders. Females and juveniles are faintly marked on the belly with scattered lighter spots. SIMILAR SPECIES In Texas, this species can only easily be confused with other large spiny lizards. Its range barely overlaps with that of the Texas Spiny Lizard (Sceloporus olivaceus), which is much more distinctly crossbanded and lacks the lateral black nuchal wedge present in the Desert Spiny Lizard. Male Texas Spiny Lizards have much smaller and fainter blue ventral patches than Desert Spiny Lizards. The Crevice Spiny Lizard (Sceloporus poinsetti) has a complete nuchal collar, a banded tail, is a dorsoventrally flattened crevice dweller, and occurs almost exclusively on rocks rather than in thickets or brush piles. DISTRIBUTION In Texas, this species occurs in Ector, Pecos, and Brewster Counties westward through the Trans-Pecos. It is absent from middle and higher elevations in the Trans-Pecos mountains. It ranges west into southern and northwestern New Mexico, much of Arizona, southwestern Colorado, southern Utah, much of Nevada, and parts of California, both in the desert eastern portions as well as the San Joaquin Valley. In Mex171

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Phrynosomatidae

Desert Spiny Lizard, juvenile, Doña Ana County, New Mexico.

ico, it occurs south throughout the Baja California Peninsula, throughout most of Sonora into Sinaloa, and south from New Mexico and Texas into Chihuahua, Coahuila, and Durango. NATURAL HISTORY In Texas, populations of these lizards are primarily associated with drainages, washes, and watercourses. The species is primarily terrestrial but does ascend shrubs, trees, yuccas, and rocks to bask. It is typically associated with dense brush and cacti and may be partial to brush and rock piles containing pack rat (Neotoma sp.) nests. The species is primarily an inhabitant of lower Chihuahuan Desert habitats, mainly along drainages and washes, but does range into desert grasslands. It feeds primarily upon insects, including beetles, ants, grasshoppers, and true bugs. We once collected a road-killed adult specimen that had recently preyed upon a large tarantula hawk wasp (Pepsis sp.), a species noted for its painful sting. In addition, hatchlings and adults of other lizards may occasionally be taken as prey. REPRODUCTION Mating and egg laying occur throughout the late spring and early summer. Females may lay several clutches of eggs a year, 2–19 eggs per clutch. Eggs incubate in about 60 days, and hatchlings measure approximately 80 mm (3.1 inches) in total length. They grow rapidly and reach sexual maturity in about 21–23 months—typically in the second summer after hatching, 172

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Desert Spiny Lizard

although some early-summer hatchlings may reach sexual maturity toward the end of their first full summer. COMMENTS AND CONSERVATION The Desert Spiny Lizard is not often encountered in most of its Texas range, and is most common in the immediate vicinity of the Rio Grande, where it inhabits brush piles and mesquite thickets in the floodplain. Some authorities recognize Texas populations as a distinct species, the Twin-spotted Spiny Lizard (Sceloporus bimaculosus), based primarily on genetic analyses comparing Arizona populations with those in Texas and New Mexico. But the area between the ranges of these 2 populations was not adequately sampled, raising questions about the validity of these conclusions. Populations of these lizards in southeastern Arizona are very similar to those occurring eastward in New Mexico and Texas, and we feel that the elevation of these populations to species status is unwarranted at this time. The Desert Spiny Lizard is protected from commercial collection and is on the TPWD’s Black List.

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Phrynosomatidae

Blue Spiny Lizard

Sceloporus cyanogenys Cope, 1885

SIZE Snout-vent length may be up to 148 mm (5.8 inches), with a total length of up to 362 mm (14.25 inches). Males are slightly larger than females. DESCRIPTION Th is is Texas’s largest spiny lizard. Although some individuals—particularly adult males—may be a bright greenish blue, in other individuals the greenish-blue coloration is much more subdued. Coloration is influenced by temperature and activity level: a brightly colored individual may change to a duller color after capture as the lizard cools. The most distinctive feature of the Blue Spiny Lizard’s pattern is its broad black nuchal collar, which usually occupies about 4 scale rows and is

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Blue Spiny Lizard, male, Jim Hogg County, Texas.

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Blue Spiny Lizard

Blue Spiny Lizard, venter, male, Jim Hogg County, Texas.

Blue Spiny Lizard, female, Starr County, Texas.

often distinctly bordered in white, both anteriorly and posteriorly. Both of these light borders are typically interrupted middorsally, and a blue spot may be present in the black collar on the sides of the neck. Paired white spots may be present on the top and back of the head, as well as less distinctly down the middle of the back. Indistinct or irregular dark spots may be present on the back in some individuals, particularly females. The dark nuchal collar extends ventrally as a thin line marking the

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division between the throat and the chest. In males, the entire throat is blue, and some of this coloration may extend onto the lower lips. The paired belly patches of the male are well separated and are also blue, without black borders. The ventral surfaces of females and juveniles lack the bluish color. The tail is indistinctly banded or not banded, and is typically bluish, even in females. Neonates are patterned like adults, but lack most of the bluish coloration. SIMILAR SPECIES The closely related Crevice Spiny Lizard (Sceloporus poinsetti) is the species most similar to the Blue Spiny Lizard. Although the 2 species closely approach each other in Kinney County, they are not known to overlap. As its name implies, the Crevice Spiny Lizard is a more dorsoventrally flattened crevice dweller, while the Blue Spiny Lizard has a rounder body. The scales of the Crevice Spiny Lizard are larger, and the body and tail more prominently ringed. The Texas Spiny Lizard (Sceloporus olivaceus) lacks the distinctive nuchal collar. All other cooccurring spiny lizards are much smaller and also lack the nuchal collar. DISTRIBUTION In Texas, the Blue Spiny Lizard occurs southwest of a line from Kinney County in the north, southeast to McMullen and Jim Wells Counties, and south to Hidalgo County. It is increasingly more common as one approaches the Rio Grande Valley. In Mexico, it ranges south through Coahuila and northern Nuevo Leon into central Tamaulipas. NATURAL HISTORY The Blue Spiny Lizard is terrestrial or semiterrestrial and prefers rather open terrain where refuges are abundant. It shows a particular affi nity for arroyos and dry watercourses, where it occupies eroded earthen banks with crevices or animal burrows. The preference for arroyos and washes makes the lizards particularly common in concrete road culverts, where several individuals may occupy seams where 2 concrete sections join. They may be found also in the vicinity of natural rock outcrops (which are infrequent in South Texas), as well as on the riprap of the dams of large reservoirs. They are commonly encountered also on abandoned buildings and brick walls, particularly those offering ample retreats. Rarely, they may be found ascending trees. Blue Spiny Lizards frequently go undetected where they are common; they are among the wariest of all spiny lizards and in many cases will retreat to cover at the first distant appearance of a potential predator or human ob-

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Blue Spiny Lizard

Blue Spiny Lizard, male, Hidalgo County, Texas.

server. Only in places with frequent human traffic do these lizards become calm enough to allow easy, though distant, viewing. Blue Spiny Lizards are sit-and-wait predators that feed on a wide variety of predominantly insect prey. REPRODUCTION Like its close relative, the Crevice Spiny Lizard (Sceloporus poinsetti), but unlike most of Texas’s other spiny lizards, the Blue Spiny Lizard is a live bearer that apparently breeds in the fall. Clutches of 5–20 live young are born in late spring; larger females produce correspondingly larger clutches. The young are about 70 mm (2.75 inches) in total length and grow rapidly. Males may reach sexual maturity in their second summer, and most females likely reach sexual maturity in their third. COMMENTS AND CONSERVATION The Blue Spiny Lizard is a locally common species that is distributed sparingly across South Texas. It seems to be primarily associated with dirt embankments, arroyos, and rock outcrops, but also uses trees, human habitations, concrete culverts, and drainage features. It is protected from commercial exploitation and is on the TPWD’s Black List. There is some taxonomic confusion regarding the identity of this species. Some authorities consider it to be conspecific with a Mexican species, Sceloporus serrifer. Although there is a morphological similarity between these 2 species, considerable differences in their DNA sequences have been detected.

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Crevice Spiny Lizard

Sceloporus poinsetti Baird and Girard, 1852

SIZE Snout-vent length may be up to 130 mm (5.1 inches), with a total length of up to 292 mm (11.5 inches). Males are larger than females. DESCRIPTION The Crevice Spiny Lizard is a robust, dorsoventrally flattened crevice-dwelling lizard. It has a body covered with noticeably large, keeled scales, giving it a somewhat “shaggy” appearance. The body is patterned with indistinct rings, and the tail is boldly and distinctly ringed with black and white. A single, broad, bold black collar encircles the neck, typically bordered in white. A small, bright blue spot is typically present

Crevice Spiny Lizard, male, Brewster County, Texas. 178

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Crevice Spiny Lizard

Crevice Spiny Lizard, female, Terrell County, Texas.

within the dark collar on the sides of the neck. Texas populations typically lack white spotting on the head. The overall dorsal ground color ranges from grayish on limestone substrates to brownish on granitic and volcanic substrates. Limestonedwelling individuals may show a faint bluish wash, but this coloration is never as pronounced as that seen in the Blue Spiny Lizard (Sceloporus cyanogenys). Both sexes may have blue throats and belly patches, but these features are brighter and larger in males. Newborns and juveniles may be more distinctly ringed on their bodies than adults. The distinctively ringed tail pattern is typically absent on individuals that have regenerated their tails. SIMILAR SPECIES The closely related Blue Spiny Lizard (Sceloporus cyanogenys) is the species most similar to the Crevice Spiny Lizard. Although the distributions of these 2 species closely approach in Kinney County, they are not known to overlap. The Blue Spiny Lizard has smaller body scales than the Crevice Spiny Lizard, and the tail is typically unringed. Furthermore, the Blue Spiny Lizard has a rounder, less dorsoventrally flattened body than the crevice-dwelling Crevice Spiny Lizard. Blue Spiny Lizards typically have white spots on the top of the head, a feature lacking in most Texas populations of the Crevice Spiny Lizard. The Texas Spiny Lizard (Sceloporus olivaceus) lacks the distinc179

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Phrynosomatidae

tive nuchal collar. The Desert Spiny Lizard (Sceloporus magister) is a brown, unringed species that is not dorsoventrally flattened and has a broad black wedge on the sides of its neck, as well as scattered yellowish spots on its flanks and faint, dark, paired spots along its spine. All other co-occurring spiny lizards are much smaller and also lack the broad nuchal collar. The Eastern Collared Lizard (Crotaphytus collaris) may appear somewhat similar to the Crevice Spiny Lizard when viewed from a distance, but it has 2 nuchal collars and a body covered in small granular scales rather than enlarged keeled scales. DISTRIBUTION The Crevice Spiny Lizard ranges from Bexar, Hays, and Mills Counties along the eastern edge of the Edwards Plateau west through the Trans-Pecos. From there it ranges north into central New Mexico and west to a few miles east of the Arizona state line. In Mexico, it ranges south along the crest of the Sierra Madre Occidental in Chihuahua and Sonora to Sinaloa and Durango, east through northern Zacatecas, and throughout Coahuila into northern San Luis Potosí and eastern Nuevo Leon. NATURAL HISTORY As its name implies, the Crevice Spiny Lizard is invariably associated with crevice-rich rocky outcrops, typically in open or semiopen country. It ranges from the tops of mountain ranges in Texas down to the rims of canyons in the Balcones Escarpment. In wooded country, it frequents exposed areas and is rarely encountered in deeply shaded situations. It is often common along rocky road cuts. The Crevice Spiny Lizard is active from March through October or early November, depending on temperatures. It is a sit-and-wait predator, feeding primarily on insects and other arthropods; ants, beetles, grasshoppers, spiders, and centipedes are documented in its diet. The Crevice Spiny Lizard is a wary, shy lizard that quickly retreats into crevices at first sight of a potential predator or human observer. It uses the noticeably large, keeled scales that cover its body to wedge itself into its crevice retreats, making extraction of these lizards from such places extremely difficult. REPRODUCTION Like its close relative the Blue Spiny Lizard, but unlike most of Texas’s other spiny lizards, the Crevice Spiny Lizard is a live bearer that breeds in the fall. After mating and the fertilization of eggs, embryonic development slows during winter brumation before accelerating in the spring. Litters of 6– 180

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Crevice Spiny Lizard

Crevice Spiny Lizard, juvenile, Jeff Davis County, Texas.

23 are born in late May or June, and neonates are about 70 mm (2.75 inches) in total length. Crevice Spiny Lizards grow fast, reaching sexual maturity in about 12 months for males and 15– 17 months for females. COMMENTS AND CONSERVATION The Crevice Spiny Lizard is a locally common or abundant species in its Texas range. It is most common in the mountains and canyons of the Trans-Pecos and only locally common in densely wooded areas along the Balcones Escarpment. It is also common in the semiopen country and granitic outcrops of the Llano Uplift. It is on the TPWD’s White List and may therefore be collected for commercial purposes. This is a large, robust lizard that can make a suitable captive, although wild adults are often so shy that they may spend much of their time hiding, even when presented with food items. They require enclosures with ample space and shelter, access to ultraviolet light, a heat gradient, and an ample, diverse, and vitaminsupplemented food supply.

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Polychrotidae

FAMILY POLYCHROTIDAE

The Polychrotidae, whose members are commonly referred to as “anoles,” consists of 392 terrestrial, semiaquatic, and arboreal species ranging throughout the New World tropics, with an important branch in the Caribbean islands. The 1 species native to the United States occurs throughout much of the southeastern United States, reaching Texas. Another 9 species have been introduced into the United States, 8 of them restricted to subtropical areas in Florida and 1 having been introduced more widely, including into Texas. Collectively, the anoles are capable of rapid color changes, from dark to light and, in some species, from brown to green. Males of most species have an extendible dewlap, or throat fan, which is usually brightly colored and used in territorial and courtship displays. Where 1 or more similar species coexist, they may competitively exclude one another—a phenomenon that has been extensively studied in the Caribbean.

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Green Anole

Green Anole

Anolis carolinensis (Voight, 1832)

SIZE Snout-vent length may be up to 75 mm (3 inches), with a total length of up to 203 mm (8 inches). Males are larger than females. DESCRIPTION Th is is a distinctively long-headed lizard with a pointed snout, slender round body, and long tail. The body is covered with numerous small granular scales. Among Texas lizards, this species is capable of the most dramatic color changes, able to shift from brown to grayish to bright green in response to changes in temperature, activity, mood, or substrate. In all cases, the belly is largely white. Males have a well-developed

Green Anole, male, Chambers County, Texas. 18 3

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Polychrotidae

Green Anole, male, Hidalgo County, Texas.

extendible throat fan. In Texas populations, the throat fan is bright pink; in females, it is largely rudimentary. Females further differ from males by having a white vertebral stripe. When stressed, as when being handled or during territorial displays, a black mask may appear in the postorbital region. During intense territorial conflicts, males may erect a short crest on the neck and upper trunk. SIMILAR SPECIES No other species in Texas is capable of such extensive color changes. The introduced Brown Anole (Anolis sagrei) is superficially similar to brown-colored Green Anoles, but has a more complex pattern of faint stripes and alternating light and dark crossbars on the body. DISTRIBUTION In Texas, this species ranges throughout most of the eastern two-thirds of the state. It may be found all along the coast from the Lower Rio Grande Valley to the Sabine River, and extends up major river systems (including the Nueces, Frio, and Colorado) into the Hill Country. Edwards, Real, and Tom Green Counties mark the westward extent of this species’ distribution. An isolated record for Brewster County at Rio Grande Village in Big Bend National Park almost certainly represents a waif that was dispersed into the region with human assistance, likely riding on a recreational vehicle from southeastern Texas. Outside Texas, this species occurs in Mexico primarily along 18 4

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Green Anole

the Rio Grande in Tamaulipas. To the east, it occurs throughout the southeastern United States, from southeastern Oklahoma, southern Arkansas, southern Tennessee, and southern North Carolina southward into the Florida Keys. NATURAL HISTORY Th is is a largely arboreal species, using tall grasses, vines, shrubs, and trees. It reaches its highest population densities in the Piney Woods of East Texas. In the drier, western portions of its distribution, it occupies riparian corridors and is rarely found far from the rivers that the species follows into these otherwise-inhospitable regions. Where the species faces competition with the introduced Brown Anole, it may be excluded from the lower parts of shrubs and vines that are occupied by its more terrestrial and aggressive relative. The Green Anole can be found active throughout the year except during the coldest parts of the winter. Like other lizards its size, it feeds on a wide variety of small arthropods.

Green Anole, female, Vernon Parish, Louisiana. 185

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Polychrotidae

Green Anole, hatchling, Edwards County, Texas.

Breeding occurs in the spring and summer. Females lay a single egg every 14–17 days. Incubation takes 30– 60 days, depending upon temperature. Hatchlings are approximately 60 mm (2.5 inches) in total length. They grow fast and reach sexual maturity by the following spring. COMMENTS AND CONSERVATION Th is species is commonly referred to as the “American chameleon” by laypersons because of its ability to change colors rapidly. But true chameleons are capable of a much wider range of color changes than the brown-to-green color changes seen in the Green Anole. Th is species is commonly seen for sale in pet stores; most such specimens are imported from out of state (particularly Florida). Since this species is a staple of the pet-store trade, it is on the TPWD’s White List and may be collected for sale in Texas. Adults can make suitable captives if their keepers are knowledgeable and provide them with an ample food supply, vitamin supplementation, and ultraviolet light. They should not be regarded as a species suitable for beginners, and most of the ones sold in pet stores undoubtedly meet an early death. The Green Anole can be quite abundant in Texas, and populations persist even in the largest cities if there is appropriate vegetation to support them and their food supplies. REPRODUCTION

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Brown Anole

Brown Anole

Anolis sagrei Duméril and Bibron, 1837 Introduced species

SIZE Snout-vent length may be up to 64 mm (2.5 inches), with a total length of up to 213 mm (8.4 inches). Males are larger than females. DESCRIPTION As its name implies, this species of anole is largely brown or brownish at all times. Although capable of color changes from a pale grayish brown to a dark chocolate brown, it is never green. Brown Anoles typically possess a light line down the back, bordered by a pattern of alternating dark and

Brown Anole, male, Hidalgo County, Texas.

Brown Anole, male, Collier County, Florida. 187

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Polychrotidae

Brown Anole, female, Collier County, Florida.

light bars restricted to the spinal region; the flanks are largely unmarked. The Brown Anole has a pointed snout, a slim, round body covered in small granular scales, and a long tail. The throat is marked by a light stripe along its midline, which in males marks the position of the dewlap or throat fan (in females, the throat fan is vestigial, but its position is still marked by a light midline stripe). The throat fan is usually a bright red orange and may be marked with chocolate and yellow. The border of the throat fan is also yellowish. When excited, males are capable of extending a crest along their spines from the nape of the neck onto their tails. SIMILAR SPECIES The Green Anole (Anolis carolinensis) may at times be brownish, but has a longer snout and lacks the patterns of dark and light color along its back. The throat fan of male Green Anoles is pink bordered in white rather than red orange bordered in yellow. Although they may be found in bushes, the Brown Anole is distinctly more terrestrial than the Green Anole. DISTRIBUTION Th is species has been introduced into the Lower Rio Grande Valley, Corpus Christi, San Antonio, and Houston area. It may be extending its range, and individuals have been observed at nurseries in several East Texas towns. Outside 18 8

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Brown Anole

Texas, it occurs widely in Florida and is native to Cuba and the West Indies. NATURAL HISTORY Th is is a largely terrestrial species that was introduced into Texas via the horticulture trade. Unlike the native Green Anole, it is not freeze tolerant, and large numbers may die off during hard winter freezes. Consequently, the species is most common in Texas in the Lower Rio Grande valley, where such freezes are infrequent. It may be active throughout the year, becoming inactive only during colder weather in midwinter. REPRODUCTION Mating and courtship occur in spring and summer. Females lay a single egg every 14–17 days, which incubates and hatches in approximately 30 days. Hatchlings are approximately 60 mm (2.5 inches) in total length. They grow fast and reach sexual maturity by the following spring. COMMENTS AND CONSERVATION The collection of this potentially invasive nonnative species is not regulated by the TPWD regulations, and so it may be collected in any quantity. A valid hunting license is nonetheless required to collect this or any other species from the wild. Intentional introduction of this species into the wild is strongly discouraged, since it has been demonstrated to adversely affect populations of the native Green Anole through vigorous competition.

Brown Anole, juvenile, Hidalgo County, Texas.

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ORDER SQUAMATA Suborder Scleroglossa Scleroglossa includes those lizards that rely primarily upon their sense of smell to locate food, including North American species in the families Eublepharidae (geckos), Scincidae (skinks), Teiidae (whiptails), and Anguidae (glass lizards and alligator lizards). In addition, this group includes all living snakes and amphisbaenians.

19 0

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Gekkota

INFRAORDER GEKKOTA

The infraorder Gekkota includes 1,437 species in 7 families, 3 of which occur natively in the United States, with a fourth family represented by numerous introduced species. In the United States, the most widespread family is Eublepharidae, which includes the banded geckos—these are widely distributed across the desert Southwest. The other 2 native families have very limited distributions: the Phyllodactylidae are represented by 1 species native to Southern California, and the Sphaerodactylidae are represented by 1 native species in extreme southern Florida. The family Gekkonidae is widely distributed throughout the tropics, and is represented in the United States by 11 introduced species.

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Eublepharidae

FAMILY EUBLEPHARIDAE

These beautifully delicate lizards are sometimes referred to as the “eyelid geckos,” since all members have moveable eyelids. Many of the species in this family have noticeably thin, delicate skin and fragile tails, which may be readily shed to avoid predation. Most species in the family are marked by noticeably banded patterns, particularly as neonates and juveniles. Unlike members of the family Gekkonidae, they are primarily ground dwellers and do not have enlarged toe pads; they are therefore not capable of clinging to smooth surfaces and walls. There are 30 species distributed across tropical and semitropical climates in the world; 4 species are found in the U.S. desert Southwest, including 2 in Texas.

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Texas Banded Gecko

Texas Banded Gecko

Coleonyx brevis Stejneger, 1893

SIZE Snout-vent length may be up to 63 mm (2.4 inches), with a total length of up to 124 mm (4.9 inches). Males and females are approximately the same size. DESCRIPTION The Texas Banded Gecko is a small nocturnal lizard with a thin, delicate skin covered in small granular scales. The skin is soft and may appear velvety. The head is proportionally large, and the light-colored eyelids are noticeably distinct against the primarily dark-patterned head. The limbs are short and comparatively weak. The tail is usually thick and marked by a basal constriction along which it often autotomizes. The thick tail serves as a fat storage organ and varies in size with food availability. When food is plentiful, it may ap-

Texas Banded Gecko, female, Brewster County, Texas.

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Eublepharidae

Texas Banded Gecko, male, Val Verde County, Texas.

19 4

pear quite fat, but during times of drought or limited food supply, it may become quite slender. The body is patterned with 5 or 6 dark brown crossbands between the nape of the neck and hips, each of them wider than the lighter, yellowish interspaces. As the animal matures, the crossbars become increasingly fragmented; much of each crossbar becomes lighter, and numerous dark spots remain. A further 7–11 dark crossbars are on the tail, and they usually remain more distinctly marked than those on the body. In a regenerated tail, the regenerated portion is lighter than the original tail, lacks crossbars, and is marked with scattered dark spots. Hatchlings and juveniles are more uniformly marked, with solid dark crossbars on a yellowish ground color. Males may be readily distinguished from females by the presence of enlarged spurs at the base of the tail. SIMILAR SPECIES In Texas, only the larger Reticulated Gecko (Coleonyx reticulatus) is likely to be confused with the Texas Banded Gecko. The Reticulated Gecko is larger as an adult, has enlarged tubercles scattered among the granular scales on its skin, has a ground color more pinkish or tannish than yellowish, and has wider interspaces between the dark bands on the body. The introduced Mediterranean Gecko (Hemidactylus turcicus) cooccurs with the Texas Banded Gecko, but has distinct toe pads, lacks moveable eyelids, lacks a distinctively banded pattern on the body, and has a distinctly warty appearance to its skin.

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Texas Banded Gecko

Texas Banded Gecko, detail of head, Coahuila, Mexico.

The Texas Banded Gecko occurs in southwestern Texas south and west of a line from Kleberg County on the South Texas coast, northwest to the southern edge of the Edwards Plateau in Bexar, Medina, and Edwards Counties, and northwest through Schleicher, Reagan, and Ector Counties. Outside Texas, it ranges from southern New Mexico into eastern Chihuahua, most of Coahuila, northern Nuevo Leon, and northwestern Tamaulipas. NATURAL HISTORY While this species may range into Tamaulipan Thornscrub and scrublands of live oak and cedar, it is most abundant in rocky or gravelly regions of the Chihuahuan Desert on flats and lower mountain slopes. It is absent from higher elevations in the mountains. The Texas Banded Gecko is a distinctly nocturnal species that retreats under rocks, fallen logs, yucca stalks, or prickly pear cactus (Opuntia sp.) pads during the day. It may use rocky crevices for retreats and, in the absence of rocks, may retreat into cracks in the soil. Although Texas Banded Geckos may be found under surface rocks and cover objects beginning in February or March, they are not surfaceactive at night until temperatures warm in April or May, and most surface activity ceases by late September or October. The lizards are most active on warm, humid nights, particularly 2– 3 nights after the infrequent summer rains. These lizards thermoregulate by pressing their bodies against warm substrates. DISTRIBUTION

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Eublepharidae

Texas Banded Gecko, juvenile, Val Verde County, Texas.

They typically walk slowly and deliberately with their tails elevated, sometimes conspicuously so. When faced with a threat of predation, they may wave their tails, drawing attention to this appendage, which can be readily autotomized and later regrown. Texas Banded Geckos feed primarily upon small insects and arachnids. REPRODUCTION Most breeding occurs from May through July. Females typically lay 2 clutches of 2 soft leathery eggs each summer. Hatchlings are about 44 mm (1.75 inches) in total length. Juveniles grow rapidly, and those hatched early in the season may reach sexual maturity by the following spring; those hatched later in the year may take 2 years to reach maturity. COMMENTS AND CONSERVATION The Texas Banded Gecko is on the TPWD’s White List and so may be collected for commercial purposes with the appropriate permits. While this species’ nocturnal nature eliminates the need for ultraviolet lighting, it does require vitamin D supplementation in its diet, and its preference for small food items complicates its captive maintenance. It is a common species, particularly in the Chihuahuan Desert region in the Trans-Pecos, and no notable population declines have been documented, although juniper encroachment along the Balcones Escarpment may be reducing the amount of suitable habitat in the eastern portions of its range. 19 6

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Reticulated Gecko

Reticulated Gecko

Coleonyx reticulatus Davis and Dixon, 1958

SIZE Snout-vent length may be up to 94 mm (3.75 inches), with a total length of up to 180 mm (7.25 inches). Males and females are of similar size. DESCRIPTION The Reticulated Gecko is a large gecko species, with a distinctly large head set off from a narrow neck and a long slender body and tail. It has a thin, delicate skin covered with velvety granular scales along with scattered rows of enlarged tubercles—a feature best viewed by using a hand lens. It has distinct, moveable eyelids and clawed toes. Its pattern consists largely of scattered brownish spots on a pinkish ground color;

Reticulated Gecko, female, Presidio County, Texas. 197

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Eublepharidae

Reticulated Gecko, detail of head, Presidio County, Texas.

the spots may form a reticulate pattern in some specimens. The tail is spotted or indistinctly banded with 8–11 bands. Hatchlings have a pattern of 5 or 6 brown body bands and a dark cap set off against a pinkish ground color, along with a distinctly banded tail. As the lizard grows, these bands and the cap rapidly fade and are replaced by the scattered dark spots present in adults. Populations inhabiting limestone canyons in the Black Gap Wildlife Management Area tend to be less densely spotted than populations from the igneous boulder fields of the mountains of the Big Bend Ranch State Park. Males may be readily distinguished from females by the presence of enlarged cloacal spurs under the skin. SIMILAR SPECIES Th is species is substantially larger than the related Texas Banded Gecko (Coleonyx brevis), with hatchling Reticulated Geckos nearly as large as adult Texas Banded Geckos. The former can further be distinguished by having a proportionally larger head, a more slender build and tail, dark bands narrower than their interspaces, a pinkish rather than yellowish ground color, and enlarged tubercles scattered among the granular skin cells. DISTRIBUTION In Texas, this species has been documented from southern Presidio and Brewster Counties. It is restricted to rugged desert mountains and canyons from east of Redford in Big 198

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Reticulated Gecko

Bend Ranch State Park east through Lajitas and Terlingua to the Christmas Mountains, throughout lower elevations of Big Bend National Park north to Persimmon Gap and throughout the Black Gap Wildlife Management Area. Much of this area is extremely remote and forbidding country. The Reticulated Gecko likely occurs north of Black Gap along the Rio Grande and may occur in the Solitario region of Big Bend Ranch State Park. In Mexico, it is known only from 1 population in northeastern Durango and another near Cuatrocienegas, Coahuila. But since substantial suitable habitat exists between the Mexican and Texas populations, it likely is more widely distributed in northern Mexico. NATURAL HISTORY The Reticulated Gecko is an inhabitant of boulder fields, cliffs, and rocky canyons in the lower Big Bend Region of the Trans-Pecos. Nocturnally surface-active from April through September, it is most commonly observed on nights immediately following summer rains. Unlike its smaller cousin the Texas Banded Gecko, it is rarely found under surface objects and presumably uses rock crevices as daytime retreats. It feeds primarily on insects and arachnids and takes considerably larger prey than the Texas Banded Gecko. REPRODUCTION As with the Texas Banded Gecko, most reproduction takes place from May through July. Females lay 2 clutches

Reticulated Gecko, female, Brewster County, Texas. 19 9

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Eublepharidae

Reticulated Gecko, female, Brewster County, Texas.

Reticulated Gecko, juvenile, Presidio County, Texas.

of 2 soft, leathery eggs each season. Hatchlings are large, with a total length of 80 mm (3.2 inches). Although the growth rate and age at sexual maturity of the Reticulated Gecko likely mirrors those of the Texas Banded Gecko, these facets of its biology have not yet been studied. COMMENTS AND CONSERVATION The Reticulated Gecko is considered a threatened species by the TPWD. At this time, approximately 20 0

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Reticulated Gecko

85 percent of its known distribution is in protected state and federal lands in Big Bend National Park, Big Bend Ranch State Park, and the Black Gap Wildlife Management Area. Research into its distribution and abundance suggests that it is much more common than was thought when the species was listed for protection, and its status as a threatened species may need to be reevaluated. This is a very charismatic species, and there is a great deal of interest in it by herpetocultural hobbyists, breeders, and commercial reptile dealers. This interest would need to be taken into consideration before changing its protected status. The species may be a candidate for the Black List, which disallows commercial trade in listed species.

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Gekkonidae

FAMILY GEKKONIDAE

The family Gekkonidae includes 917 species worldwide, 11 of which have been introduced into the United States. Of these, only 1 species has become widely established in Texas; 3 others are represented by small colonies that do not appear to be spreading. The gekkonids are primarily nocturnal, with large eyes and vertical pupils but without moveable eyelids. They are notable climbers; many species have intricately scaled toe pads that enable them to climb surfaces as smooth as panes of glass. While the members of most species are small in size, individuals in the largest species reach total lengths in excess of 360 mm (14 inches). Gekkonids, unlike most lizards, are able to vocalize. Most species produce a short series of clicks that are used to signal territoriality and likely to attract mates.

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Rough-tailed Gecko

Rough-tailed Gecko

Cyrtopodion scabrum (Hayden, 1827) Introduced species

SIZE Snout-vent length may be up to 51 mm (2 inches), with a total length of up to 117 mm (4.6 inches). Males are larger than females. DESCRIPTION The Rough-tailed Gecko is aptly named, having a tail covered with enlarged, distinctly keeled scales. It has enlarged claws on bent toes and lacks toe pads. Like other typical geckos, it lacks eyelids and has vertically elliptical pupils. Its ground color is a pale, sandy tan, which is covered with scattered, dark brown spots. The spots appear to coalesce on the tail and form indistinct bands near the tail tip. Its skin is cov-

Rough-tailed Gecko, adult, Galveston County, Texas. 203

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Gekkonidae

ered with small granular scales interspersed with noticeably enlarged tubercles. SIMILAR SPECIES The Mediterranean Gecko (Hemidactylus turcicus) has toe pads and a paler pattern and lacks the prominently keeled caudal scales. The Indo-Pacific Gecko (Hemidactylus garnoti) and Common House Gecko (Hemidactylus frenatus) are larger and much paler as adults, with a far less distinct pattern when active, and have vaguely flattened tails. Indo-Pacific Geckos have a yellowish to orange venter and a lateral fringe of scales on the tail, while Common House Geckos have several rows of fringing scales on the tails. Like the Mediterranean Gecko, these 2 species have distinct toe pads, which are lacking in the Rough-tailed Gecko. DISTRIBUTION In the United States, this species is restricted to the immediate vicinity of the Port of Galveston. It has been present in this area since 1983, does not appear to have spread beyond the initial colony, and can still be commonly found at the port. It is native to the Middle East, from Egypt east to India. NATURAL HISTORY Th is species is active on warm nights beginning in March through November. In Texas, it occurs primarily on the ground and on buildings in warehouse complexes associated with the Port of Galveston. In its native range, it occupies gravelly and rocky washes, slopes, and canyons. REPRODUCTION Mating may occur throughout the active season, and females lay several clutches of 2 eggs at intervals during the season. The eggs are laid in spaces in the walls of buildings and hatch in 45–55 days. Hatchlings are about 34 mm (1.25 inches) in total length. They grow rapidly and may reach sexual maturity in a single season. COMMENTS AND CONSERVATION As an introduced species, the Rough-tailed Gecko is not regulated by the TPWD, and it may be collected in any quantity by someone with a valid Texas hunting license. In captive trials, this species has been shown to aggressively displace both Mediterranean Geckos and the native Texas Banded Gecko (Coleonyx brevis). On Galveston Island, it appears to have largely replaced the Mediterranean Gecko in the immediate vicinity of the port. Because of its potential to compete with the native Texas Banded Gecko, further introduction of this species beyond Galveston Island is strongly discouraged. 20 4

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Common House Gecko

Common House Gecko

Hemidactylus frenatus Duméril and Bibron, 1836 Introduced species

SIZE Snout-vent length may be up to 60 mm (2 inches), with a total length of up to 127 mm (5 inches). Males and females are similarly sized. DESCRIPTION Th is is a small, rather smooth-skinned gecko, with distinct toe pads and large eyes that have elliptical pupils but lack moveable eyelids. The skin is covered in small granular scales that are interspersed with 6 longitudinal rows of slightly enlarged, keeled scales on the tail. Its ventral surface is whitish. The dorsal pattern varies considerably between periods of

Common House Gecko, juvenile, Querétaro, Mexico.

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Gekkonidae

Common House Gecko, adult, Tamaulipas, Mexico. Photo by Tim Burkhardt.

nocturnal activity and diurnal inactivity. At night, the dorsal ground color is tan or pinkish with a pattern of faint wavy crossbands on the body. During the day, this color darkens considerably and may appear to be dark grayish, and the crossbars become much more distinct. Scattered light flecks may be also present, by day or night. SIMILAR SPECIES The Common House Gecko is frequently confused with the Indo-Pacific Gecko (Hemidactylus garnoti), from which it can be distinguished by its yellow to orange ventral surfaces and its fringe of enlarged caudal scales. The Mediterranean Gecko (Hemidactylus turcicus) and the Rough-tailed Gecko (Cyrtopodion scabrum) are covered with enlarged skin tubercles and have dorsal patterns consisting of scattered dark spots. No other Texas lizards lack moveable eyelids. DISTRIBUTION Currently, this species occurs in Texas only in Dallas and Tarrant Counties on the grounds of the Dallas Zoo and the Fort Worth Zoo; a single specimen has also been recorded in Galveston. In the United States, it has become established at sites in the Florida peninsula and the Florida Keys. It is thought to be native to tropical Asia but may be found throughout the tropics and is well established in tropical regions of Mexico. NATURAL HISTORY In tropical regions and southern Florida, this species is active year-round. Cold weather during the winter in 20 6

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Common House Gecko

north-central Texas restricts the activity of this population to March through October or November. U.S. populations are typically encountered on the walls of human habitations, both indoors and out. They feed on small insects and arachnids, both by actively foraging along walls or by ambushing insects that may be attracted to lights. The Common House Gecko is known to vocalize to advertise the possession of territory to other conspecifics. REPRODUCTION Mating and egg laying may occur throughout the active season, with females annually laying several clutches of 2 eggs each. Eggs may be laid as individual clutches or communally by several females. They are deposited in the interspaces of walls, in crevices, or under debris on the ground. The eggs incubate in about 50 days, and hatchlings are about 60 mm (2 inches) in total length. They grow rapidly and may reach sexual maturity in a single season. COMMENTS AND CONSERVATION As an introduced species, the Common House Gecko is not regulated by the TPWD, and it may be collected in any quantity by someone with a valid Texas hunting license. There are only 2 small, highly localized populations in Texas, which originated from the escape of lizards brought to the zoos as feeder animals for lizard-eating snakes. Further introduction of this exotic species is discouraged. Th is species should be watched for at ports along the Texas coast and in the Lower Rio Grande Valley.

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Gekkonidae

Indo-Pacific House Gecko

Hemidactylus garnoti Duméril and Bibron, 1836 Introduced species; unisexual species

SIZE Snout-vent length may be up to 64 mm (2.5 inches), with a total length of up to 133 mm (5.25 inches). DESCRIPTION The Indo-Pacific House Gecko lacks moveable eyelids and has vertically elliptical pupils. It has distinct toe pads, which enable it to cling to vertical surfaces, including panes of glass. Its thin, delicate skin is covered in tiny granular scales that lack enlarged tubercles. The tail is flattened, with a row of enlarged fringing scales along its length. The ventral surfaces are yellowish to orange, and the underside of the tail is darker than the belly. Dorsal ground color varies dramatically between day and night. When the lizard is active, at night, it is rather pale and largely monochromatic, appearing light tan or pinkish overall, and the large, dark eyes standing out dramatically from the lighter body. When resting during the day, the lizards darken considerably and may appear to be dark grayish mottled with darker blotches and streaks, along with scattered light spots. This coloration camouflages the lizard during periods of inactivity. SIMILAR SPECIES Compared to the more widespread Mediterranean Gecko (Hemidactylus turcicus), the Indo-Pacific House Gecko is larger, has smoother skin and a fringe of scales on its flattened tail, and has a yellowish to orange venter, quite unlike the tubercle-covered, round-tailed, and white-bellied Mediterranean Gecko. It can be distinguished from the Common House Gecko (Hemidactylus frenatus) by its yellowish or orange venter. Furthermore, the Common House Gecko has 6 rows of enlarged 20 8

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Indo-Pacifi c House Gecko

scales on its tail rather than a single fringing row. The Roughtailed Gecko (Cyrtopodion scabrum) lacks toe pads and has noticeably enlarged tubercles on its skin and enlarged keeled scales on its tail. All other Texas lizards have moveable eyelids. DISTRIBUTION Currently, this species occurs in Texas only in Dallas and Tarrant Counties on the grounds of the Dallas Zoo and the Fort Worth Zoo. In the United States, it occurs in New Orleans, southern Georgia, and parts of the Florida peninsula, where it is declining in numbers because of competition from another, larger introduced species, the Tropical House Gecko (Hemidactylus mabouia). As its common name implies, the Indo-Pacific House Gecko is native to India, Southeast Asia, and the islands of the South Pacific. NATURAL HISTORY In the United States, this species is primarily associated with human habitations and trash dumps. In its native range, it may be found using trees for feeding and refuge. It is nocturnal and feeds primarily on insects and arachnids either by actively foraging along walls or by sitting in wait near lights. In warm regions, it may be active year-round, but in Texas, where its activity is limited by cold weather, it can be found from March through September or October. As a species, it is not very freeze tolerant, and it remains to be seen whether the populations in north-central Texas will persist.

Indo-Pacific House Gecko, adult, Sarasota County, Florida. Photo by Terry L. Hibbitts. 20 9

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Gekkonidae

REPRODUCTION The Indo-Pacific House Gecko is an all-female species—males are unknown. It reproduces via the development of unfertilized eggs in a process known as parthenogenesis. Courtship activities have been observed in this species, but the extent to which these behaviors are necessary for egg development are not well known. Females lay multiple clutches of 2 eggs each throughout the active season. Eggs are laid in spaces within the walls of buildings or under leaf litter and take about 50 days to hatch. Hatchlings are 55 mm (2 inches) in total length and may reach sexual maturity in a single season. COMMENTS AND CONSERVATION As an introduced species, the IndoPacific Gecko is not regulated by the TPWD, and it may be collected in any quantity by someone with a valid Texas hunting license. There are only 2 small, highly localized populations existing in Texas, which originated from the escape of lizards brought to the zoos as feeder animals for lizard-eating snakes. Since this is a parthenogenetic, unisexual species, a single escaped female could found a new population of this potentially invasive species; further introduction of this exotic species is discouraged. This species should be watched for at ports along the Texas coast and in the Lower Rio Grande Valley.

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Mediterranean Gecko

Mediterranean Gecko

Hemidactylus turcicus (Linnaeus, 1758) Introduced species

SIZE Snout-vent length may be up to 60 mm (2 inches), with a total length of up to 127 mm (5 inches). Males and females are similarly sized. DESCRIPTION The Mediterranean Gecko has large lidless eyes with vertically elliptical pupils, expanded toe pads, and a body covered with small granular scales liberally interspersed with enlarged tubercles. Its basic ground color is tan or pinkish with scattered brown spots. The spots may be more intensely marked during the day, and the ground color may darken to a brownish tan. The ventral surface is whitish. The brown dorsal spots may

Mediterranean Gecko, adult, Harris County, Texas. 211

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Gekkonidae

Mediterranean Gecko, hatchling, Kinney County, Texas.

coalesce on the tail to form prominent bands posteriorly. The head is flattened and distinct from the neck. SIMILAR SPECIES Unlike the Common House Gecko (Hemidactylus frenatus) and the Indo-Pacific House Gecko (Hemidactylus garnoti), the Mediterranean Gecko has noticeably enlarged tubercles on its skin. The presence of enlarged toe pads and the lack of enlarged keeled scales on the tail further distinguish this species from the Rough-tailed Gecko (Cyrtopodion scabrum). All other Texas lizards have moveable eyelids. DISTRIBUTION Th is species has been documented from most major cities in the southern two-thirds of the state, and it likely occurs in most or all communities in this region. Cold winter temperatures probably limit its distribution, and it is not known from the Texas Panhandle. It can be found primarily in major cities across the southern tier of states, from California to South Carolina. As its common name implies, it is native to the Mediterranean region. NATURAL HISTORY In the United States, this species is primarily associated with human habitations and structures, as well as trash dumps, where the lizard or its eggs may have been transported along with human refuse, particularly building materials. It is only infrequently encountered away from such places, but can be seen on rocky cliffs created by highway road cuts in the west212

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Mediterranean Gecko

ern part of the Balcones Escarpment and Edwards Plateau. In its native range, it occurs primarily in rocky canyon country. It feeds mostly on small insects, which it may stalk by actively foraging along walls, or it may wait for such insects to be attracted to lights. It is active year-round in extreme southern Texas, but its activity is restricted by cold weather in northern regions. It is usually encountered beginning in March through October or November. REPRODUCTION Courtship and breeding typically occur throughout the animal’s active season. Females lay several clutches of 2 eggs annually. Clutches may be laid individually or communally. The eggs are hard-shelled and adhere to the surface upon which they are laid. Eggs may be laid in wall interspaces, behind books on bookshelves, in crevices, or under flower-bed debris. Eggs incubate for about 50 days. Hatchlings are about 60 mm (2 inches) in total length. COMMENTS AND CONSERVATION As an introduced species, the Mediterranean Gecko is not regulated by the TPWD, and it may be collected in any quantity by someone with a valid Texas hunting license. In captive trials, this species has been shown to retreat from aggressive displays by the Texas Banded Gecko (Coleonyx brevis) and the Rough-tailed Gecko (Cyrtopodion scabrum). In Florida, this species has been replaced in many areas by several larger species in the genus Hemidactylus, including the Common House Gecko (Hemidactylus frenatus), the Indo-Pacific House Gecko (Hemidactylus garnoti), and the Tropical House Gecko (Hemidactylus mabouia). Although the deliberate introduction of this invasive exotic species is discouraged, it is clear that the species is now a permanent part of Texas’s lizard fauna.

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Scincomorpha

INFRAORDER SCINCOMORPHA

The infraorder Scincomorpha includes approximately 2,363 species of small to medium-large lizards in 6 families, 3 of which are native to the United States—the Scincidae, Teiidae, and the Xantusiidae. The Scincidae include the familiar backyard skinks, which in North America reach their greatest species diversity in the southeastern Coastal Plains. The Teiidae include North American whiptails and race runners, which (in contrast to the Scincidae) reach their greatest species diversity in the desert Southwest. The Xantusiidae is a comparatively small family of tropical and desert-adapted species collectively referred to as “night lizards” (although not all species are nocturnal). In the United States, this family is known primarily from species occupying the Sonoran and Mojave Deserts, and is not represented by species in Texas.

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Scincidae

FAMILY SCINCIDAE

Skinks are most readily recognized by their covering of shiny, overlapping, cycloid (circular-edged) scales, each of which contains a bony osteoderm (literally, “skin bone”). North American skinks are secretive, and species may be fossorial (burrowers), semifossorial, inhabitants of forest leaf litter, or semiarboreal; some tropical species may also be aquatic. Within the family, the length of a given species’ legs is typically strongly correlated to its lifestyle. Most fossorial species are limbless (primarily seen in African and Australian species) or nearly so (many species worldwide, including the Florida Sand Skink, Plestiodon reynoldsi). At the other extreme, semiarboreal species such as the Broad-headed Skink (Plestiodon laticeps) have strong legs with long toes. Most species exhibit dramatic changes in coloration as they mature, with the hatchlings and juveniles of most species having the brightest markings. During breeding season, the males of most species develop bright orange markings on their lips, cheeks, or throats, and in some cases this coloration may extend to their entire heads. After egg laying, female skinks typically guard their nests, coiling protectively around their eggs. This behavior helps to avoid both predation and desiccation of the clutch. Globally, the Scincidae is represented by 1,553 species, 14 of which occur natively in the United States, including 8 in Texas. Another 6 species have been introduced into the US (primarily southern Florida) from elsewhere.

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Scincidae

Coal Skink

Plestiodon anthracinus (Baird, 1850)

SIZE Snout-vent length may be up to 70 mm (2.75 inches), with a total length of up to 178 mm (7 inches). Males and females reach similar sizes. DESCRIPTION The Coal Skink is a primarily brown lizard with wide, dark brown or black lateral stripes bordered by 2 light lines. Counting the light lines, this is a four-lined skink. In this species, the dark lateral lines extend onto the snout forward of the eyes, a feature distinguishing it from the other 2 species of four-lined skinks in Texas. Further, the dark lateral fields between the light lines are 2.5–4 scales wide. The tail is robust and

Coal Skink, male, Natchitoches Parish, Louisiana. 216

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Coal Skink

Coal Skink, female, Pushmataha County, Oklahoma. Photo by Marla P. Hibbitts.

thick and serves as a fat-storage organ. Reproductively active males develop an orange wash on their lips and chins. Hatchlings are black, with blue tails and reddish spots on top of the head. Most hatchlings lack the light lines present in adults, but some may be faintly marked. SIMILAR SPECIES Ground Skinks (Scincella lateralis) are smaller and more slender, lack light-colored stripes, and have transparent “windows” on their lower eyelids. Prairie Skinks (Plestiodon septentrionalis) have dark lateral stripes that are not wider than 2 scale rows, and the dark lateral lines do not extend forward of the eyes. While immature Five-lined Skinks (Plestiodon fasciatus) are readily distinguished by the presence of a middorsal light line, that species shows a dramatic color change from striped juveniles to dully patterned adults. While male Five-lined Skinks rapidly lose most traces of pattern, females typically retain some striping, and in some cases the middorsal stripe may be completely obscured. In these cases, the Five-lined Skink is typically larger, has stronger limbs, and a thinner tail. Making an identification based on these subjective features is possible only if an individual has experience with both species. When in doubt, check the postmental scale beneath the chin: Coal Skinks have 1 postmental scale, while Five-lined Skinks have 2. The Four-lined Skink (Plestiodon tetragrammus) does 217

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Scincidae

Coal Skink, male, Jasper County, Texas.

not overlap geographically with the Coal Skink. In the Fourlined Skink, the light lateral lines stop before the base of the tail (in most Texas populations, usually just behind the forelimbs), while in the Coal Skink, the light lateral lines extend onto the tail. The black hatchlings of Coal Skinks are superficially similar to hatchling Great Plains Skinks (Plestiodon obsoletus) but are much smaller, and Great Plains Skinks have oblique lateral scale rows. The ranges of the 2 species do not overlap in Texas. DISTRIBUTION Texas populations of the Coal Skink occupy the eastern fourth of the state with the exception of the immediate coastal plain and Big Th icket, extending west to Henderson and Anderson Counties. Outside Texas, this species’ range is highly discontinuous, with a large range extending north and east across Louisiana, Oklahoma, Arkansas, southeastern Kansas, and Missouri. East of the Mississippi River, the range is highly fragmented, with widely scattered populations from Mississippi and Florida north to New York. NATURAL HISTORY The Coal Skink is widely distributed across the eastern fourth of Texas, primarily in the Piney Woods region and the extreme eastern edge of the Post Oak Savannah. It is most often encountered in moist habitats such as streamsides, springs, hillside seepage bogs, and sphagnum-lined ponds. It is a secretive species that is rarely observed active on the sur218

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Coal Skink

face; it forages by searching beneath grasses, leaf litter, logs, or other cover objects. It feeds primarily on small insects, arachnids, and other arthropods. Its activity period ranges from early March until November, and it is likely inactive during midsummer heat and drought. REPRODUCTION The courtship and reproduction of Texas populations are poorly known. In Louisiana, we have found males displaying nuptial colors in March, and a female guarding a clutch of eggs was found in southeastern Oklahoma in early May. Females lay a single clutch of 4–10 eggs, which they presumably guard throughout the incubation period. Hatchling coal skinks are approximately 50 mm (2 inches) in total length, and presumably reach sexual maturity in 1 year. COMMENTS AND CONSERVATION Th is secretive species is rarely observed in Texas, and the status of Texas populations is unclear and in need of investigation. It seems to be most common in open, sandy forests deep in the Piney Woods region. It is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Scincidae

Prairie Skink

Plestiodon septentrionalis Baird, 1859 “1858”

SIZE Snout-vent length may be up to 90 mm (3.5 inches), with a total length of up to 224 mm (8.75 inches). Males and females are similarly sized. DESCRIPTION The Prairie Skink is primarily brown, brownish gray, or olive gray in color, with 2 light lateral lines on each flank bordering a broader dark line that is less than 2 scale rows wide. In this species, both the light and dark lines extend onto the tail, but not anterior to the eyes onto the snout. A faint middorsal light line may be present in some specimens, but the back in most individuals is monochromatic and patternless. Th is is

Prairie Skink, male, Wise County, Texas. 220

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Prairie Skink

Prairie Skink, female, Wise County, Texas. Photo by Terry L. Hibbitts.

a distinctly short-legged, long-tailed species, and the tail may be quite thick in a well-fed and healthy individual. Reproductively active males may display bright orange coloration on their lips. Hatchlings resemble adults, but with brighter patterns and a blue tail. SIMILAR SPECIES Texas’s other four-lined skinks overlap in distribution with the Prairie Skink. Four-lined Skinks (Plestiodon tetragrammus) have light lateral lines that end anterior of the hind limbs, and in most cases well before the hind limbs. Coal Skinks (Plestiodon anthracinus) have wider dark lateral lines covering 2.5–4 scale rows, as opposed to no more than 2 in the Prairie Skink. Furthermore, the light lateral lines extend anterior of the eyes and onto the snout in the Coal Skink. Coal Skinks further have a single postmental scale under their chins, whereas Prairie Skinks have 2 postmental scales. Ground Skinks (Scincella lateralis) are much smaller and more slender, lack light lateral stripes, and have transparent “windows” on the lower eyelids. DISTRIBUTION In Texas, this species occurs east of a line from Wichita Falls and San Saba south to Atascosa County. Populations are absent from extreme southeastern Texas in the Big Thicket. It ranges north through the eastern Great Plains to Minnesota and Saskatchewan. 221

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Scincidae

As its name implies, this species occurs primarily on the Rolling Plains. It formerly occupied much of the Blackland Prairie before it was converted to agriculture. It ranges east onto the Post Oak Savannah and into grassy areas in the Piney Woods, where it has declined greatly in recent years as the land has increasingly been converted to closed-canopy thickets and pine plantations. The species is active from late March through November, and may undergo periods of dormancy during midsummer when conditions become hot and dry. It feeds primarily on small insects and arachnids. REPRODUCTION Courtship and breeding occur in spring, usually in April. Females lay 2–18 eggs in the late spring. The female deposits these eggs in a burrow, typically beneath a large rock or other cover object in a place that retains moisture throughout the incubation period. Eggs hatch in 45–65 days. Hatchlings are about 50 mm (2 inches) in total length. COMMENTS AND CONSERVATION The Prairie Skink is on TPWD’s Black List and so may not be collected for commercial purposes. Populations in the eastern portion of its range have experienced declines as its grassy habitat has been converted to closedcanopy woodlands. It remains common on the Rolling Plains of north-central Texas. NATURAL HISTORY

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Four-lined Skink

Four-lined Skink

Plestiodon tetragrammus Baird, 1859 “1858”

SIZE Snout-vent length may be up to 75 mm (3 inches), with a total length of up to 200 mm (7.9 inches). Males and females are similarly sized. DESCRIPTION The Four-lined Skink has 2 light lateral stripes bordering a dark field that do not extend beyond the hind legs. In most Texas populations north of the Lower Rio Grande Valley, the light lines barely extend beyond the front legs. Along the Rio Grande in extreme south Texas, the light lines may reach the hind legs. The body may bear a faint Y-shaped marking extending from the snout onto the forehead. Its ground color ranges from brown to gray; the largest specimens generally exhibit the

Four-lined Skink, male, Val Verde County, Texas.

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Scincidae

Four-lined Skink, female, Crockett County, Texas.

lightest coloration. Reproductively active males show orange coloration on their lips. Hatchlings and juveniles are more vividly marked than adults; they have darker ground colors, lighter stripes, and a bright blue tail, which fades rapidly as the lizard grows. The light stripes on the head may be orange, particularly in the youngest specimens. Proportionally, this is a long-bodied, long-tailed skink with relatively short legs. The tail is thick and serves as a fat-storage organ. SIMILAR SPECIES The Prairie Skink (Plestiodon septentrionalis), which occurs with this species primarily on the Rolling Plains, has lateral stripes that extend onto the tail, as does the Coal Skink (Plestiodon anthracinus), which does not co-occur with the Four-lined Skink. Many-lined Skinks (Plestiodon multivirgatus) either have numerous alternating light and dark lines or lack lines altogether. The Great Plains Skink (Plestiodon obsoletus) is far larger, has an irregular pattern of dark-bordered dorsal scales that form irregular stripes, and has oblique scale rows on its flanks. The Ground Skink (Scincella lateralis) is smaller, more slender, lacks light lines bordering its dark lateral stripe, and has a transparent “window” in its lower eyelid. DISTRIBUTION The Four-lined Skink occurs primarily west of the Balcones Escarpment, ranging from the vicinity of Corpus Christi north along the escarpment to Wise County and reach224

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Four-lined Skink

Four-lined Skink, male, Cameron County, Texas.

ing the northern extent of its distribution in Baylor County. Its range follows the western edge of the Rolling Plains south to San Angelo and west into the Trans-Pecos, reaching the western extent of its range in Hudspeth County. In Mexico, it ranges through Coahuila, Nuevo Leon, Tamaulipas, and San Luis Potosí to northern Veracruz. NATURAL HISTORY In the Lower Rio Grande Valley, this species may be active year-round, becoming inactive only during infrequent cold spells. Throughout most of the state, the species is active beginning in early spring through late fall in October or November. During the hottest and driest parts of the summer, it may undergo periods of inactivity or retreat underground. It inhabits the Tamaulipan Thornscrub, oak and juniper canyons and plateaus on the Edwards Plateau, oases and uplands in the Chihuahuan Desert, and grasslands on the Rolling Plains. It is a secretive species that restricts most of its activity to dense vegetation, leaf litter, or rock rubble. When it must cross an open space, it does so quickly in a “mad dash,” reaching cover as quickly as possible. It may occasionally ascend trees to bask. It feeds primarily upon small insects and other terrestrial arthropods. REPRODUCTION Courtship and breeding occur primarily in the spring. Females lay a single clutch of 3–12 eggs once a year, 225

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Scincidae

typically in a depression under rocks or in their shelter. Like most skinks, females have been observed attending their eggs throughout incubation. Hatchlings emerge in July or August and are about 50 mm (2 inches) in total length. They grow quickly and may reach adult size by the following spring. During the breeding season, males frequently show signs of combat, with evidence of bite marks and missing scales on their heads and bodies. COMMENTS AND CONSERVATION Th is is the most common species of skink throughout much of central and southwestern Texas. It is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Five-lined Skink

Five-lined Skink

Plestiodon fasciatus (Linnaeus, 1758)

SIZE Snout-vent length may be up to 86 mm (3.4 inches), with a total length of up to 215 mm (8.5 inches). Males and females are similar in size. DESCRIPTION The Five-lined Skink is a medium-sized skink with a stout body, strong legs, and a long, slender tail. Hatchlings are black overall with 5 light lines—2 lateral lines on each side of the body and a single middorsal stripe—extending from the snout down the body and onto the tail. These stripes are white or yellow on the head and body and then blend in with the brilliant blue coloration on the tail. As this species matures, it undergoes

Five-lined Skink, male, Jasper County, Texas. 227

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Scincidae

Five-lined Skink, female, Franklin County, Texas.

a dramatic ontogenetic color change: the black ground color lightens to brown and the light stripes darken to gray or tan. The brilliant blue tail fades to gray; in the largest individuals, it may be brown like the rest of the body. Most females remain distinctly striped throughout life; the back is brown and lighter than the darker lateral field. Unlike the striped females, the oldest mature males may be uniformly brown, with only the barest vestiges of the stripes remaining. Males develop bright orange on their jaws, faces, and heads during breeding season, and the jaws may be somewhat expanded laterally. Th is orange coloration fades by early summer to a dull orangish brown. SIMILAR SPECIES Th is species is confusingly similar to the closely related but larger Broad-headed Skink (Plestiodon laticeps). Adults of both species are similarly colored: males have brown bodies and orange or orangish heads; females are usually brownish overall with darker lateral fields and 5 faded stripes. But a mature Broad-headed Skink is much larger. In general, a juvenile-colored skink that is within the size range of an adult Five-lined Skink is likely to be a Broad-headed Skink. Typically, the stripes on Broad-headed Skinks are narrower than on Fivelined Skinks, and this feature can become a fairly reliable indicator as one gains experience in observing a large number of specimens. But certain identification of hatchlings, juveniles, 228

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Five-lined Skink

and smaller females of these 2 species should be determined by scale characteristics. Broad-headed Skinks lack enlarged postlabial scales, having 1 large labial scale broadly in contact with the ear opening. Five-lined Skinks show 2 small postlabial scales in the same area. Furthermore, most Broad-headed Skinks have 5 supralabials anterior to the eye, while most Five-lined Skinks have 4 anterior supralabials. Make sure to examine the supralabials on both sides of the head if possible, since the number of supralabials may vary from one side of the head to the other. Some female Five-lined Skinks may lack a light middorsal stripe at maturity, and thus can be confused with Coal Skinks (Plestiodon anthracinus) or Prairie Skinks (Plestiodon septentrionalis). But the Five-lined Skink is distinctly longer limbed than either and has a thinner tail. Further, the Coal Skink has a single postmental scale under the chin, while the Five-lined Skink has 2 postmental scales. DISTRIBUTION Th is species ranges across the eastern third of Texas, east of a line from Wise and Somervell Counties in the north to Refugio County in the south. Beyond Texas, it ranges north to southeastern Nebraska, east to the Great Lakes region in Wisconsin, Michigan, and southern Ontario, across Pennsylvania, and with limited distribution in eastern New York and parts of Vermont and Connecticut. It occurs throughout the southeastern United States, but is absent from most of peninsular Florida. An isolated population occurs in Minnesota. NATURAL HISTORY The Five-lined Skink primarily occurs in forested areas of Texas and is most common in riparian lowlands. On the western edge of its Texas distribution, it may follow river corridors into grassland habitats. Th is is a primarily arboreal species, but nonetheless spends a great deal of time near the ground. It is especially common around downed trees and brush piles in forests. It is commonly seen basking on tree trunks. It may ascend high into trees in search of prey, particularly to dead and decaying snags that harbor large populations of insects. Insects and other terrestrial arthropods make up the bulk of this species’ diet. The Five-lined Skink is primarily active beginning in early spring, from March through November. During the hottest parts of the summer, its activity may be restricted to the early-morning hours. This species is more visible than most skinks, and can commonly be observed basking and 229

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Scincidae

Five-lined Skink, juvenile, Polk County, Texas.

foraging in exposed sites. Quite wary, it will make a quick dash for nearby cover when approached. REPRODUCTION Courtship and mating occur in the spring, typically in April or May. Males are quite aggressive to other males during this time, and many individuals will show bite marks and scarring on their heads and bodies. Females lay eggs in a depression excavated under logs, rocks, or other surface cover and may nest inside fallen or standing dead trees. Clutches contain 3–12 or more eggs, and the female attends the nest throughout the incubation period, which lasts 55–65 days. Hatchlings are about 60 mm (2.25 inches) in total length and reach adult size in approximately 1 year. COMMENTS AND CONSERVATION Th is species is common to abundant throughout most of East Texas. It is on the TPWD’s White List and so can be collected for commercial purposes with the appropriate permits. It is fairly suitable for captivity, but as a basking species does require ultraviolet light. Care should be taken that its caging conditions do not become too dry.

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Broad-headed Skink

Broad-headed Skink

Plestiodon laticeps (Schneider, 1801)

SIZE Snout-vent length may be up to 143 mm (5.6 inches), with a total length of up to 324 mm (12.75 inches). Males and females are approximately the same size. DESCRIPTION Th is is Texas’s second-largest skink, surpassed in size only by the Great Plains Skink (Plestiodon obsoletus). Adult males, with their solid brown bodies and broadly enlarged heads—brilliant orange during the breeding season—are unmistakable. Juveniles begin life as black lizards with 5 white or yellow dorsal stripes extending from the snout onto the tail. There are 2 lateral stripes on each side of the body, and 1 verte-

Broad-headed Skink, male, Liberty County, Texas. 231

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Scincidae

Broad-headed Skink, female, Liberty County, Florida.

bral stripe down the middle of the back. The tail is bright blue. As the animal matures, the stripes begin to fade, the ground color lightens to brown, and the tail color shifts from blue to gray. Adult females retain the lateral stripes, and the dark field between them is typically darker than the back. The light vertebral stripe may be only faintly indicated on the broad brown back. Adult males may retain a hint of striping, but most are a solid, dull brown on their bodies, limbs, and tail. Their heads become quite enlarged, with the jaws and temporal region expanded. During breeding season, the entire head may be bright orange. In adults of both sexes, the body is stout, the limbs are proportionally long for a skink, and the tail is long and slender. Adult males usually have regenerated tails as a result of territorial combat with other males. SIMILAR SPECIES The closely related but substantially smaller Fivelined Skinks (Plestiodon fasciatus) are extremely similar in all aspects of color and pattern, particularly as juveniles. In general, a Broad-headed Skink retains its juvenile coloration well into the adult size range (or larger) of the Five-lined Skink, and very large juveniles can often be safely assumed to be Broadheaded Skinks. The stripes on Broad-headed Skinks are narrower, but this characteristic is subjective, and many specimens need to be examined before the use of this characteristic can be 232

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Broad-headed Skink

considered reliable. Examination of the scales on the head provides the most consistent determination of species in this complex. Broad-headed Skinks usually have 5 supralabials in front of the eye (be sure to check both sides, since there may rarely be 4 on one side) and lack enlarged postlabial scales. DISTRIBUTION In Texas, this species occurs east of a line from Cooke County on the Red River south through Bosque and Williamson Counties to Victoria County on the Texas Coast. Outside Texas, it ranges across the southeastern United States from southeastern Oklahoma and extreme southeastern Kansas across most of Missouri through the southern parts of Illinois, Indiana, and Ohio to western West Virginia. It occurs south through most of Kentucky and Tennessee, but is absent from the higher portions of Appalachia. Its distribution resumes in North Carolina, eastern Virginia, and Maryland; it reaches the northernmost extent of its range in extreme southeastern Pennsylvania. It occurs throughout the southeastern Coastal Plain, but is absent from the southern half of the Florida Peninsula. NATURAL HISTORY The Broad-headed Skink is Texas’s most arboreal skink, and is most commonly encountered in close association with standing hollow trees, both live and dead. It may be encountered in forested regions throughout eastern Texas, but is most abundant in bottomland hardwood forests associated with major rivers. It is most typically sighted basking or foraging along tree trunks or branches, often well out of reach, many feet above the ground. When found basking or foraging on the ground, it typically flees to a nearby tree, which often has holes in its buttressed trunk leading to its hollow core. Occasionally a specimen may be seen retreating into a mammal burrow, such as those dug by armadillos. Although it feeds primarily on terrestrial arthropods—most commonly, insects—it is capable of consuming smaller lizards, nestling mice, and possibly nestling songbirds. REPRODUCTION Courtship and mating occur primarily in April and May, and eggs are laid from May to June. During the breeding season, encounters between adult males often result in territorial disputes, which may involve savage biting of the heads, flanks, legs, and tails of the combatants. During this season, males typically exhibit evidence of these encounters as bite marks, missing scales, broken tails, and missing toes and feet. 23 3

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Scincidae

Females typically lay 5–15 eggs and attend them throughout the incubation period, which lasts 55–65 days. Eggs are laid in a cavity excavated beneath a cover object such as a fallen log, board, or piece of corrugated sheet metal. Given this species’ arboreal nature, it is also likely that some clutches are laid within cavities inside of standing trees, both live and dead. Hatchlings are about 80 mm (3 inches) in total length and typically reach adult size in about a year. COMMENTS AND CONSERVATION Th is species is on the TPWD’s Black List and so cannot legally be collected for commercial purposes. But the difficulty in distinguishing juveniles of this species from the Five-lined Skink (which is on the White List) undoubtedly results in at least some juvenile Broad-headed Skinks entering the reptile marketplace. Although this species is quite common in East Texas, it has likely suffered significant population declines as its preferred river-bottom habitats have been inundated by the creation of reservoirs and impoundments along most Texas rivers. Because of its large size and varied diet, it can make a suitable captive, but since it is a confirmed basker, it will do best when housed with ultraviolet lighting and given food supplemented with vitamin D.

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Many-lined Skink

Many-lined Skink

Plestiodon multivirgatus Hallowell, 1857

SIZE Snout-vent length may be up to 76 mm (3 inches), with a total length of up to 194 mm (7.6 inches). Females on average are slightly larger than males. DESCRIPTION The Many-lined Skink is a short-legged, long-tailed skink that in Texas occurs in 2 distinct color or pattern morphs. In all specimens, ground coloration ranges from light gray to tan. Belying the common name, some individuals are a completely patternless gray or tan. In other individuals, up to 20 alternating light and dark stripes run from the head onto the tail (or up to 10 dark stripes on an otherwise light ground color). These stripes may become broken or irregular on the tail. Dur-

Many-lined Skink, male, Crockett County, Texas.

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Scincidae

Many-lined Skink, female, Crockett County, Texas.

ing the spring breeding season, males develop orange coloration on the lips and may have slightly enlarged jaws. The tail in this species is thick and serves for nutrient storage. Hatchlings are black with a bright blue tail and may show faint striping at the time of emergence from the egg. This coloration fades rapidly as the skink matures, with adult coloration acquired within a few months (although the tail may remain bluish after the adult coloration is reached). SIMILAR SPECIES No other species is particularly similar to the unique Many-lined Skink. Patternless Many-lined Skinks could be confused with adult Four-lined Skinks (Plestiodon tetragrammus), but that species always has 4 light lines at least on the head and neck. Ground Skinks (Scincella lateralis) have dark lateral stripes and are much more slender. Striped-phase Many-lined Skinks are superficially similar to adult Great Plains Skinks (Plestiodon obsoletus), but that species is much larger, and Great Plains Skinks comparable in size to adult Many-lined Skinks would still show either the black hatchling coloration or transitional orange juvenile colors. DISTRIBUTION In Texas, the Many-lined Skink ranges from Donley County in the Texas Panhandle south to Crockett, Schleicher, Irion, and Reagan Counties southwest of San Angelo. Isolated records exist in the Trans-Pecos in Pecos, Brewster, Presidio, 236

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Many-lined Skink

Many-lined Skink, patternless male, Lincoln County, New Mexico.

Culberson, and Hudspeth Counties. Outside Texas, it ranges west through New Mexico into Arizona to the Grand Canyon, and north into southeastern Utah and southwestern Colorado. East of the Rocky Mountains, it occurs in northeastern Colorado, southeastern Wyoming, most of Nebraska, and southern South Dakota. NATURAL HISTORY In Texas, this species occurs primarily in 2 general habitats: on short-grass prairies from the southern Panhandle to the vicinity of San Angelo, and on limestone mountain slopes in the Trans-Pecos. In general, its active period ranges from late February through October or November, with peak activity closely correlated to available surface moisture. On the prairies, it is most commonly encountered under surface objects such as flat limestone slabs from late March through May. In the Guadalupe Mountains and Glass Mountains of the Trans-Pecos, it is more commonly encountered on the surface in late summer following monsoonal rains. Plant associations include buffalo grass, gamma grasses, Texas beargrass, mesquite, and juniper on the grasslands, and piñon, juniper, oak, and ponderosa pine in the mountains. It is known to feed on a wide variety of terrestrial arthropods, chiefly insects. REPRODUCTION Courtship and mating occur in the spring; males have been encountered displaying the orange nuptial color237

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Scincidae

Many-lined Skink, hatchling, Torrance County, New Mexico.

ation on the lips throughout the month of April. Females lay clutches of 3–9 eggs from late May to June, typically in a depression excavated underneath a cover object such as a large rock. They attend the eggs throughout the incubation period of approximately 2 months. Hatchlings are about 64 mm (2.5 inches) in total length. They grow rapidly and reach adult size in about a year. COMMENTS AND CONSERVATION The Many-lined Skink is the most poorly known skink in Texas in regard to the extent of its distribution, behavior, and natural history. It is known from widely separated populations in West Texas that inhabit short-grass prairies and montane areas in the ranges of the Trans-Pecos. Texas populations are likely relictual—the fragmented remnants of a once-widespread distribution. It is on the TPWD’s Black List and so may not be collected for commercial purposes. Patternless morphs are more common in the TransPecos mountains; striped morphs predominate on the shortgrass prairies west of San Angelo and on the High Plains near Lubbock.

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Great Plains Skink

Great Plains Skink

Plestiodon obsoletus Baird and Girard, 1852

SIZE Snout-vent length may be up to 143 mm (5.6 inches), with a total length of up to 349 mm (13.75 inches). Males and females are approximately equal in size. DESCRIPTION Th is is Texas’s largest skink. It is unique among Texas skinks in that it has oblique rather than horizontal lateral scale rows. In adults, the dorsum is grayish, tan, or faintly olive, with irregular and vaguely indicated stripes resulting from the edges of each dorsal scale being marked with black (this is usually most strongly indicated on the sides of each scale). The scales on the face are likewise outlined in black, creating a net-

Great Plains Skink, male, Throckmorton County, Texas. 23 9

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Scincidae

Great Plains Skink, female, Edwards County, Texas.

work of dark lines. The scales on the ventral surfaces are lighter in color, and the light ventral coloration develops into the dorsal pattern about halfway up the flanks. The flanks are usually lightly marked with a scattering of orange or salmon-colored spots. In some specimens, the tail may bear a rich yellowish or straw color. The body is thick and stout, and the legs are short. In those few individuals encountered with an unregenerated tail, the tail is about 1.5 times as long as the body, and may be quite thick, particularly when food and water are plentiful. Males and females can be distinguished by the shape and size of the head: in females, the head is not distinct from the neck and appears rather small and pointed; in males, the jaws and temporal regions widen significantly at maturity, making the head noticeably distinct from the neck. Hatchlings are colored completely differently from adults. Hatchlings have jet-black bodies and dark blue tails; they were originally described as belonging to a different species. There are bright white spots on the labials, snout, and scales above the eyes. As the young lizard grows, the scales begin to lighten from the centers in an irregular pattern, with the centers of scales first turning orange, resulting in a dark lizard with an irregular pattern of orangish stripes. As it continues to grow, the orange color predominates, and the young lizard comes to resemble a miniature adult with orange 24 0

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Great Plains Skink

rather than tan or gray scales. Eventually, the orange coloration fades across most of the body, leaving the adult coloration of tan or gray with scattered orange flecks on the flanks. SIMILAR SPECIES No other Texas skink closely resembles the Great Plains Skink at any stage of its life. Adults may be vaguely similar to the Many-lined Skink (Plestiodon multivirgatus), but are far larger. In fact, a Great Plains Skink in the size range of an adult Many-lined Skink would still show the black juvenile coloration or the earliest stages of the transitional subadult coloration. Furthermore, Many-lined Skinks have horizontal rather than oblique lateral scale rows. DISTRIBUTION In Texas, the Great Plains Skink occurs west of a line from Grayson County in the north, south through Milam County to San Patricio County in the south. In Mexico, it occurs in northern Tamaulipas, throughout Nuevo Leon and Coahuila, and in northern Zacatecas, northeastern Durango, eastern Chihuahua, and extreme northeastern Sonora. In the United States, it ranges from Texas west through southern and eastern New Mexico and into the highlands of central Arizona; north across the Great Plains states from the front range of the Rocky Mountains in Colorado to southern Nebraska, throughout Kansas and most of Oklahoma, east to the western edges of Arkansas, Missouri, and extreme southwestern Iowa. NATURAL HISTORY As its name indicates, the Great Plains Skink is most abundant on the plains and is particularly common where rock outcrops have been eroded out of hillsides, with the resulting rock slabs resting on otherwise loose, sandy, or loamy soils. In Texas, it is most common in the Rolling Plains region and along the Caprock canyons in the Texas Panhandle. It may be found throughout the Hill Country, Trans-Pecos, and Ta maulipan Thornscrub regions, although in much lower population densities than in the Rolling Plains. It is capable of excavating its own burrows beneath surface rocks where the soil is loose enough to allow burrowing. In rockier regions, it may inhabit natural rock crevices. Since its range is across the breadth of Texas’s latitudinal range, its seasonal activity period varies greatly from north to south. In extreme southern Texas, it may be active beginning in early February and ending in December—and in fact may occasionally be seen on warm days throughout the winter. In the far northern regions of the Texas 241

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Scincidae

Great Plains Skink, hatchling, Jeff Davis County, Texas.

Panhandle, its activity period may not begin until around the first week of April, and winter weather may curtail its activity by the end of October. Although capable of burrowing, it is primarily active in sheltered areas aboveground and under cover, using rodent runs beneath grass on the prairies or within taluscovered slopes in rockier areas. In the Chihuahuan Desert, it may be active at night, particularly during midsummer. REPRODUCTION Courtship and breeding occur primarily in the spring, usually in April or May, with eggs laid approximately 1  month after copulation. Females lay clutches of 7–24 eggs, which hatch in approximately 60 days. Hatchlings typically appear in late July or early August. Although adult size may be reached in its second summer, this species takes 3 years to reach sexual maturity. Males develop wide jaws and enlarged heads and may engage in rather violent territorial combat when they encounter one another. COMMENTS AND CONSERVATION Th is largest of Texas skinks can be quite abundant, particularly in the Rolling Plains region. But its abundance is not evenly distributed across its wide range— in some areas, it is only infrequently encountered. It has undoubtedly suffered declines in some areas from the conversion of rangeland into farmland. It is on the TPWD’s White List and is therefore eligible for commercial collection. It is among the 24 2

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Great Plains Skink

Great Plains Skink, juvenile, Dimmitt County, Texas.

most suitable of Texas lizards for the home terrarium, since it basks infrequently in the wild and does not require ultraviolet light; however, it does benefit from vitamin supplementation. The species undergoes the most dramatic ontogenetic color change of any Texas lizard species, from black hatchlings to pale gray adults. Adults and hatchlings were originally described as separate species because of this dramatic difference in color and pattern.

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Scincidae

Ground Skink

Scincella lateralis (Say, in James, 1823)

SIZE Snout-vent length may be up to 57 mm (2.25 inches), with a total length of up to 146 mm (5.75 inches). Males and females are similarly sized. DESCRIPTION The Ground Skink is a tiny, slender species with a long tail and very short legs. It has a dark brown to nearly black lateral stripe running from the snout through each eye, down the flanks, and onto the tail. Above this lateral stripe, the ground color ranges from a pale golden brown to a dark chocolate brown not much lighter than the side stripes. Below the lateral stripes, its color is paler, usually some shade of gray. In some individuals, the underside of the abdomen is suff used with yellow. Among Texas skinks, this species is unique in having a transparent “window” on the lower eyelid, through which it can presumably see when the eyes are closed. Sexual dimorphism is not known in this species, and hatchlings are colored identically to adults. SIMILAR SPECIES In Texas, all other similarly colored skinks are larger, have a pattern including light lateral lines, and lack the transparent “window” on the lower eyelids. DISTRIBUTION Th is species occurs in Texas east of a line from Wichita Falls in the north, south through San Angelo to the Pecos River in Pecos and Terrell Counties. On the western edge of its range, the distribution is quite fragmented. Although it has been recorded in most counties south of the Balcones Escarpment, it is not commonly encountered in that region. It occurs throughout the southeastern United States, from Texas north to

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Ground Skink

Kansas and east to Maryland and south to the southern tip of Florida and the Florida Keys. An isolated population occurs in Coahuila, Mexico. NATURAL HISTORY The Ground Skink is a diurnal lizard that rarely strays from the security of forest leaf litter, where it searches for and feeds upon diminutive arthropod prey—primarily insects. It occurs mainly in forested areas, but may follow riparian corridors along major rivers into more xeric regions. At the western edge of its range, it occurs in sheltered canyons where relictual pockets of oaks provide habitat remnants in an otherwiseinhospitable region. Throughout most of Texas, this species is surface-dwelling throughout the year, retreating for shelter only during severely cold weather. REPRODUCTION Courtship and reproduction occur from January through August. Females lay clutches of 1–7 eggs and may lay multiple clutches a year. Females may nest communally in depressions within or under logs or other cover objects. Unlike Texas skinks in the genus Plestiodon, female Ground Skinks are not known to attend their clutches. Hatchlings are about 44 mm (1.75 inches) in total length and may reach sexual maturity in about a year.

Ground Skink, adult, San Augustine County, Texas.

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Scincidae

COMMENTS AND CONSERVATION The Ground Skink is one of the most abundant lizards in East Texas, and is on the TPWD’s White List. The bulk of the commercial trade in this species supplies the demand for “feeder lizards” for juvenile snakes. Its diminutive size makes it unsuitable for captivity for all but the most advanced keepers.

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Teiidae

FAMILY TEIIDAE

The family Teiidae includes 140 species of primarily active, diurnal predators ranging in size from tiny species such as the Little Striped Whiptail (Aspidoscelis inornata) of the southwestern United States to relative giants such as South America’s Red and Black Tegus (Tupinambis sp.). All are active foragers that locate prey with forked tongues, and some are amongst the swiftest and wariest lizard species. There are 22 species in the United States, primarily in the desert Southwest, 11 of them (in the genus Aspidoscelis) in Texas. All Texas species have granular dorsal scales, enlarged rectangular ventral scales, and enlarged scales on the tails. All whiptail species are active, nervous species that make poor captives because they require ample heat, ultraviolet light, and a large and varied food supply. We have observed that most adult whiptails have a shorter activity season than that of most Texas lizards. Teiids emerge in the spring to forage, replenish winter fat losses, and begin the reproductive season. Breeding continues through the end of July in most species, and then most adults take refuge until the next breeding season, even though ambient temperatures are adequate for activity. This behavior is thought to reduce the risk of predation on breeding adults and also to reduce competition with their conspecific juveniles. Texas whiptails are represented both by sexually reproducing species and by all-female species that reproduce through parthenogenesis. Although it is unclear precisely how that ability arose in whiptails, it is clear that all the parthenogenetic species arose through the hybridization of 1 or more sexual species. In parthenogenetic species, all offspring are genetically identical clones of their parent. Populations of these all-female species therefore consist of lineages of clones, some of which may have arisen from separate hybridization events. Although these species are all-female, courtship and copulatory behaviors appear to be important, perhaps necessary, for the development of eggs, and these species engage in these behaviors quite similar to those seen in sexually reproducing species. In parthenogenetic species, females undergo fluctuating hormonal cycles in which individuals with high estrogen levels behave like females, and those with low estrogen levels behave like males. Male-acting individuals engage in pseudocopulation. They as247

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sume a stereotypical copulatory position (much like that seen in sexually reproducing whiptails), biting female-acting individuals just in front of the hips and wrapping their bodies about them in a loop, bringing their cloacas into close proximity. Th is pseudocopulation stimulates egg development in female-acting individuals. After eggs have been laid, estrogen levels plummet and the individual assumes a male-like role in the population. Individuals alternate between male-like and female-like roles throughout the reproductive season (there are usually not more than 2 role reversals and therefore 2 clutches of eggs per season).

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Texas Spotted Whiptail

Texas Spotted Whiptail

Aspidoscelis gularis (Baird and Girard, 1852)

SIZE Snout-vent length may be up to 105 mm (4.1 inches), with a total length of up to 280 mm (11 inches). Males are larger than females. DESCRIPTION Th is is a medium to large, striped and spotted whiptail species with 7 or 8 light dorsal stripes and with light spots present in the dark fields between the stripes. In most specimens, the dorsal stripes have a distinctly greenish cast; the tail is reddish in all but the oldest adults. Mature males have pink or orangish throats coupled with a blue or blue-black venter; the bellies and throats of females are unmarked. Juveniles have

Texas Spotted Whiptail, Val Verde County, Texas. 24 9

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Teiidae

Texas Spotted Whiptail, venter, male, Val Verde County, Texas.

Texas Spotted Whiptail, female, Dimmitt County, Texas.

more distinctly marked stripes, mostly lack the light spots in the dark fields between the stripes, and have distinctly reddish tails and rumps. As with all whiptails, the body is covered with small granular scales, and the venter with large rectangular scutes. SIMILAR SPECIES Six-lined Racerunners (Aspidoscelis sexlineata) are generally smaller and lack spots in their dark fields. Males have a uniformly blue venter and throat rather than the pink 250

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Texas Spotted Whiptail

throat and blue-black venter seen in the Texas Spotted Whiptail. The Laredo Striped Whiptail (Aspidoscelis laredoensis) is an allfemale species that is either unspotted or only faintly spotted on the lower sides; its tail is greenish rather than reddish, and the hind limbs are marked by noticeably reticulated patterns. The Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis), an allfemale species, is drabber, without the greenish coloration present in the Texas Spotted Whiptail. It has a pattern of light spots overlapping the light dorsal stripes, and the spots on the rump are yellowish. The venter is pale and always lacks the blue coloration of the Texas Spotted Whiptail. The Little Striped Whiptail (Aspidoscelis inornata) is considerably smaller as an adult, lacks greenish coloration and light spots in the dark fields between the stripes, and has a bright blue throat, venter, and—frequently—tail. The Marbled Whiptail (Aspidoscelis marmorata), Rusty-rumped Whiptail (Aspidoscelis septemvittata), and Common Checkered Whiptail (Aspidoscelis tesselata) are marked by varying degrees of marbled and reticulated patterns, and lack the greenish color on the dorsum. DISTRIBUTION The Texas Spotted Whiptail occurs throughout most of Central Texas. Its range does not extend into the western portions of the Trans Pecos, the High Plains in the Texas Panhandle, or the Piney Woods of deep East Texas. It ranges into southern Oklahoma just north of the Red River and into extreme southeastern New Mexico from Carlsbad eastward. In Mexico, it occurs in Coahuila, Tamaulipas, Nuevo Leon, Zacatecas, extreme eastern Durango, San Luis Potosí, Queretaro, Guanajuato, and eastern Jalisco. NATURAL HISTORY Like most whiptails, the Texas Spotted Whiptail is an insectivore, feeding on termites, grasshoppers, crickets, beetles, caterpillars, and spiders. It searches for these insects by probing with its snout through leaf and grass litter, with frequent tongue flicking, which enables it to detect potential prey by scent. The lizards may be observed turning such leaf litter with their forelimbs. Their primary activity periods occur when temperatures are 35°C–40°C (95°F–104°F). In midsummer, when midday temperatures exceed this range, they may retreat to subterranean burrows or seek areas of deep shade in which to forage. They occupy open and semiopen habitats from the Rolling Plains, Blackland Prairies, Post Oak Savannah, Cross Timbers, 251

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Texas Spotted Whiptail, male, Uvalde County, Texas.

Texas Spotted Whiptail, hatchling, Fisher County, Texas.

Edwards Plateau, and Tamaulipan Thornscrub. They may be found also on the eastern edges of the Chihuahuan Desert. They may be particularly common in riparian zones along major rivers, probably because of ample food supplies in those areas. REPRODUCTION Females may become sexually receptive beginning in April; most courtship and reproduction occurs in the late spring (May–June). A single clutch of 1–8 eggs is laid in July, typ252

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Texas Spotted Whiptail

ically in a chamber within the female’s burrow. Eggs have been discovered in abandoned rodent burrows as well as in road embankments. The red-tailed hatchlings emerge in late summer, measuring 25–40 mm (1.0–1.5 inches) in snout-vent length. They grow rapidly and reach sexual maturity in a single season. COMMENTS AND CONSERVATION The Texas Spotted Whiptail is one of the most abundant lizards in Central and South Texas. Through hybridization, it is a parental contributor to the parthenogenetic Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis) and the Laredo Striped Whiptail (Aspidoscelis laredoensis). It is on the TPWD’s White List and so may be collected for commercial purposes. Most specimens entering the commercial trade are undoubtedly sold as food for lizard-eating snakes.

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Rusty-rumped Whiptail

Aspidoscelis septemvittata (Cope, 1892)

SIZE Snout-vent length may be up to 115 mm (4.5 inches), with a total length of up to 320 mm (12.5 inches). Males are larger than females. DESCRIPTION Th is species has 6 or 7 broad longitudinal white stripes on a dark ground color. Large white spots are found within the dark ground fields between the stripes, and these spots merge with the sides of the light stripes, particularly toward the rear of the abdomen, and may isolate portions of the dark fields into distinct dark squares or checkers. The white lines and spots are often large enough that some specimens may have the appearance of a whitish lizard with dark stripes or

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Rusty-rumped Whiptail, male, Brewster County, Texas.

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Rusty-rumped Whiptail

Rusty-rumped Whiptail, female, Brewster County, Texas.

spots. The hips and the base of the tail are distinctly rusty colored, and a bluish cast may be present on the forelimbs and the tip of the tail. The belly and throat are usually white or pale blue, and females may have a light orange color on their throats. Juveniles are similar to adults but are more distinctly striped, and the light spots in the dark fields are generally smaller. SIMILAR SPECIES The closely related Texas Spotted Whiptail (Aspidoscelis gularis) has greenish dorsal coloration, shows a less reticulated pattern (with light spots distinct from the light lines rather than in contact with them), and lacks the distinctive rusty rump and tail. The Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis), an all-female species, also has well-separated light lines and spots and is a much more drably colored species than the Rusty-rumped Whiptail, lacking the distinctive rusty rump. The 2 all-female species of checkered whiptails (Aspidoscelis dixoni and Aspidoscelis tesselata) have a more fragmented pattern resulting from the fusion of light lines with large light spots. The Marbled Whiptail (Aspidoscelis marmorata) has a rather uniform marbled dorsal pattern lacking distinct spots or stripes. The Little Striped Whiptail (Aspidoscelis inornata) lacks light spots in the dark fields altogether and is a much smaller species. DISTRIBUTION In Texas, the Rusty-rumped Whiptail occurs from the vicinity of Dryden in eastern Terrell County west through the southern portions of Pecos County, throughout most of

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Rusty-rumped Whiptail, male, Presidio County, Texas.

Brewster County south of the Glass Mountains, southern Presidio County, and portions of Hudspeth County along the Rio Grande. In Mexico, it ranges south through eastern Chihuahua and into central Coahuila. NATURAL HISTORY The Rusty-rumped Whiptail lives in open canyons and hillsides in the Chihuahuan Desert region of West Texas, often in close association with dense stands of “shin dagger,” or lechuguilla (Agave lechuguilla). Its primary activity periods occur when temperatures are 35°C–40°C (95°F–104°F), which, in the desert habitat typically happens in early to midmorning and again in late afternoon. During the heat of midday, they retreat into underground refugia, although where they occur along watercourses or at desert oases, they may retreat to areas of deep shade. These lizards are active foragers, pushing through and turning over gravel and detritus with their snouts and forelimbs in search of insect prey, which may be located either by sight or by use of their acute sense of smell. They have been observed to feed on termites, grasshoppers, crickets, beetles, caterpillars, and spiders. REPRODUCTION Much like its eastern relative, the Texas Spotted Whiptail (Aspidoscelis gularis), females of the Rusty-rumped Whiptail may become reproductively receptive by mid-April, but most courtship and reproduction occurs in May and June. 256

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Rusty-rumped Whiptail

Females deposit 1–5 eggs in July, presumably in a refuge burrow, but this has not been documented for this species. Hatchlings emerge in late summer and measure 25–40 mm (1.0–1.5 inches) in snout-vent length. They grow rapidly and reach sexual maturity in a single season. COMMENTS AND CONSERVATION The taxonomic history of this species remains confused in the literature. Recent publications regard it as a subspecies of the Texas Spotted Whiptail (Aspidoscelis gularis) or the Mexican Plateau Whiptail (Aspidoscelis scalaris). In Texas, the species occurs adjacent to (and maybe overlapping with) the Texas Spotted Whiptail on the Stockton Plateau and in the northern Trans-Pecos, apparently with only little evidence of hybridization or intergrades occurring. Th is arrangement also exists in central Coahuila, Mexico. It remains unclear whether this lizard and the Mexican Plateau Whiptail overlap or intergrade, and the relationship between the 2 forms remains poorly understood. Recognizing the Rusty-rumped Whiptail as a full species best reflects our understanding of the form’s evolutionary and biological identity. In Texas, the species may be locally abundant in canyons and on lower mountain slopes and hillsides, primarily in the southern Trans-Pecos. Genetically, it is a parental contributor to the parthenogenetic Gray Checkered Whiptail (Aspidoscelis dixoni) and Common Checkered Whiptail (Aspidoscelis tesselata). It is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Little Striped Whiptail

Aspidoscelis inornata (Baird, 1859 “1858”)

SIZE Snout-vent length may be up to 70 mm (2.75 inches), with a total length of up to 240 mm (9.4 inches). Males and females are similar in size. DESCRIPTION Th is is a small-bodied whiptail, with 7 (occasionally 6) light dorsal stripes on a dark brown or blackish ground color. The throat, belly, undersides of the legs, and tail are blue; coloration is more intense in males than females. The upper surfaces of the hind limbs may be unmarked and uniformly colored. The dark fields between the stripes are unspotted. Juveniles are miniature versions of adults, but are not as intensely marked with blue.

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Little Striped Whiptail, male, Hudspeth County, Texas.

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Little Striped Whiptail

Little Striped Whiptail, female, Presidio County, Texas.

Within its range, only the Desert Grassland Whiptail (Aspidoscelis uniparens) and Six-lined Racerunner (Aspidoscelis sexlineata) have unspotted dark fields at all ages. The all-female Desert Grassland Whiptail differs in that its ventral surface is typically unmarked and whitish, its tail is brown or greenish, and it has only 6 light dorsal stripes. Where the Little Striped Whiptail and Six-lined Racerunner occur together, adults of the latter have a greenish wash on the forebody and lack a blue tail. Juveniles of other species may appear to have unspotted dark fields at a distance, but close examination will reveal that their dark fields are faintly spotted. DISTRIBUTION In Texas, the Little Striped Whiptail occurs from Howard and Kinney Counties west through the Trans-Pecos. It also occurs throughout central New Mexico. Populations formerly assigned to this species from Arizona have been described as a distinct species. It occurs in Mexico in Chihuahua, Coahuila, Durango, Zacatecas, and San Luis Potosí. NATURAL HISTORY Th is species occurs in grassland and desert grassland areas and prefers open bare ground interspersed with shrubs and grasses. It rarely pauses in the open, darting from bush to bush, where it forages in typical whiptail fashion, probing surface detritus with its snout and digging through cover materials with its forelimbs. It feeds primarily on small insects, and termites may be a preferred prey when available. It is active SIMILAR SPECIES

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at body temperatures from 38°C–40°C (100°F–104°F) and may remain in the cover of shade or retreat underground when daytime highs exceed that range. REPRODUCTION Breeding and courtship occur primarily in May and June, and oviposition in June and July. Females lay 1 or 2  clutches of 1–3 eggs annually, presumably in chambers associated with burrows constructed as midday refuges. Hatchlings are miniature versions of adults, but with paler blue bellies. They measure about 28 mm (1.1 inches) in snout-vent length, and Texas populations typically reach sexual maturity in a year or less. COMMENTS AND CONSERVATION The Little Striped Whiptail is a relatively common to abundant species in the Trans-Pecos region. Through hybridization, it has donated its genome to produce the following parthenogenetic species: the Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis), the New Mexico Whiptail (Aspidoscelis neomexicana), and the Desert Grassland Whiptail (Aspidoscelis uniparens). Recent taxonomic changes have resulted in several populations of this species outside Texas being elevated to species status, although these changes are not yet widely accepted. Although common, this species is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Marbled Whiptail

Marbled Whiptail

Aspidoscelis marmorata (Baird and Girard, 1852)

SIZE Snout-vent length may be up to 107 mm (4.25 inches), with a total length of up to 305 mm (12 inches). Males are larger than females. DESCRIPTION The Marbled Whiptail has a pale gray or tan ground color with pale spaces surrounded by darker gray or brownish (rarely blackish) markings that tend to form reticulations on the sides and rear of the abdomen. Hints of striping may be present on the neck and upper back of some individuals. A great deal of variation is present in the size and degree of reticulation. Some individuals have reticulations so fi ne that they result in a vaguely “salt and pepper” appearance, while others have

Marbled Whiptail, Brewster County, Texas.

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Marbled Whiptail, Winkler County, Texas.

larger markings giving the appearance of as few as 15–20 lateral bars. Adult males have a dark throat and venter. Juveniles are distinctly striped on the forebody, with 6 light lines on a grayish brown ground color. The lines break up posteriorly near the hind limbs into dots, dashes, and reticulations. As the lizards mature, the degree of reticulation increases until the adult pattern is reached. Some populations, especially near the Monahans Sandhills of Crane and Ward Counties, are completely patternless. SIMILAR SPECIES The Marbled Whiptail is most similar to the all-female Gray Checkered Whiptail (Aspidoscelis dixoni) and Common Checkered Whiptail (Aspidoscelis tesselata). Both of those differ from the Marbled Whiptail in being all-female species and having more distinct dorsal checkering, particularly in the case of the Common Checkered Whiptail. The Rustyrumped Whiptail (Aspidoscelis septemvittata) is similar in color to the Marbled Whiptail, but more distinctly striped, often with a bluish tail and forelimbs. No other whiptail species is quite so large or so typically unstriped. DISTRIBUTION In Texas, this species occurs primarily in the deserts of the Trans-Pecos, with populations ranging northeastward into the Monahans Sandhills and the Permian Basin. An isolated record for this species exists from Webb County 262

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Marbled Whiptail

along the Rio Grande. It occurs in central and southern New Mexico, particularly along the Rio Grande and Pecos River drainages, and ranges south into the Mexican states of Chihuahua, Coahuila, and northwestern Nuevo Leon. NATURAL HISTORY The Marbled Whiptail prefers flat, open areas of desert pavement scattered with scrub bushes such as mesquite and creosote. It may be found along desert washes, on the gravelly alluvial slopes at the bases of mountains and foothills, and in brush-covered sand dune fields. The movements of this extremely wary species are rapid and jerky, and these lizards seem to be in a constant state of motion as they patrol their loosely held territories. Typically, they move rapidly and deliberately across open spaces and slow down upon reaching the shelter of shrubs, where they scrape and probe through surface detritus in search of insect prey, including beetles, grasshoppers, ants, insect larvae, butterflies, moths, and termites. When available, termites may make up most of this species’ diet. It may be active at high temperatures, maintaining its body temperature at around 40°C (104°F). At higher temperatures, the lizards fi rst retreat to the limited shade of desert shrubs and then into burrows, whether dug by the lizards themselves or abandoned by burrowing mammals such as ground squirrels and kangaroo rats.

Marbled Whiptail, Brewster County, Texas. Photo by Marla P. Hibbitts. 26 3

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Reproduction and courtship occur in the late spring and early summer, and egg laying may occur in late June or July. A single clutch of 1–5 eggs is laid in an underground burrow. The first hatchlings appear by the end of July and continue to hatch through August and early September. Hatchlings are about 44 mm (1.7 inches) in snout-vent length. They grow and mature rapidly and may reach sexual maturity in a single year. COMMENTS AND CONSERVATION The Marbled Whiptail is an abundant species that occurs in some of Texas’s most desolate habitats. Analyses have shown this species to be a genetic contributor to several all-female parthenogenetic species through hybridization, including the Gray Checkered Whiptail (Aspidoscelis dixoni), the Common Checkered Whiptail (Aspidoscelis tesselata), and the New Mexico Whiptail (Aspidoscelis neomexicana). In the older literature, this species was considered a subspecies of the Western Whiptail (Aspidoscelis tigris), which occurs from Arizona westward. The Marbled Whiptail is on the TPWD’s White List and so may be collected for commercial purposes. Most specimens entering the commercial trade are undoubtedly sold as food for lizard-eating snakes. REPRODUCTION

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Six-lined Racerunner

Six-lined Racerunner

Aspidoscelis sexlineata (Linnaeus, 1766)

SIZE Snout-vent length may be up to 86 mm (3.4 inches), with a total length of up to 267 mm (10.5 inches). Females are slightly larger than males. DESCRIPTION The Six-lined Racerunner has 6 or 7 (rarely 8) dorsal stripes. Eastern populations typically have 6 (rarely 7) stripes, and western ones have 7 (rarely 8). In western adults, the middorsal stripe(s) may be faded and indistinct. The throat and belly of males are light blue in all populations, and the females

Six-lined Racerunner, male, Lamar County, Texas. 265

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are usually white in these areas. The dorsal stripes may be white or pale yellow. In Texas populations outside the Piney Woods, a greenish wash is typically seen on the flanks and face of most adults; males are more intensely colored than females. In some specimens, the green coloration is so intense as to wash out the dorsal stripes, particularly anteriorly on the flanks. East Texas specimens often show some degree of green coloration as well, particularly in males, but the development of greenish color is not as extensive as it is in western populations. Some populations on sandy plains deep in South Texas have the yellowish coloration on the face. Hatchlings and juveniles have yellow or white stripes on a dark field and have blue-tipped tails. SIMILAR SPECIES The only other whiptail that occurs sympatrically with the Six-lined Racerunner and that lacks spots in the dark fields between the stripes is the Little Striped Whiptail (Aspidoscelis inornata). Where these 2 forms coexist, the Little Striped Whiptail is smaller, more boldly marked with blue on the throat, belly, and tail, and lacks the greenish wash present in western populations of the Six-lined Racerunner. All other cooccurring species have light spots in the dark fields between the stripes. DISTRIBUTION In Texas, this species has been documented to occur almost statewide except in the Trans-Pecos. But its abundance is quite variable, and it can be quite rare, particularly in areas of Central and South Texas on rocky or gravelly soils. Beyond Texas, it occurs in eastern New Mexico, eastern Colorado, and southeastern Wyoming east through southern South Dakota, most of Nebraska, the southern two-thirds of Missouri, parts of Illinois and Indiana, western Kentucky, most of Tennessee, and North Carolina north through Virginia to Maryland. It ranges throughout the Deep South into the Florida Keys, being absent only from the Everglades and the lower Mississippi River Delta. To the north, it follows the Mississippi River Valley into central Minnesota. Although this species occurs in coastal regions near Brownsville, it has not been recorded from Mexico. NATURAL HISTORY Th is species prefers open grassy areas interspersed with open soil. It reaches its highest population densities on sandy soils. It is not commonly encountered on the rocky, gravelly, or clay soils preferred by the Texas Spotted Whiptail (Aspidoscelis gularis). Activity begins in April and peaks in June 266

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Six-lined Racerunner

Six-lined Racerunner, male, Jasper County, Texas.

Six-lined Racerunner, venter, male, Jasper County, Texas.

and July. Adults may seem to disappear in late summer or early fall after the emergence of hatchlings. Hatchlings (and the occasional adult) can be observed until the onset of cold weather, usually in October or early November. The Six-lined Racerunner is active over a range of body temperatures, 36°C–42°C (97°F–108°F). During the spring, early summer, and fall, this species may be active all day. In midsummer, its daily activity 267

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cycle is distinctly bimodal, since it retreats to dense shade or underground burrows to avoid midday heat. Like all members of the genus, Six-lined Racerunners are active foragers and search through their environments in typical whiptail fashion by probing and scraping through surface detritus for their arthropod prey; spiders and grasshoppers seeming to be preferred dietary items. Termites, leafhoppers, beetles, ants, moths, and butterflies have also been documented in their diets. REPRODUCTION Reproductive activity occurs primarily in May and June. A female lays 1 or 2 clutches of 1–6 eggs throughout the summer, frequently in a burrow dug by the female into a sandy substrate. Eggs incubate in 46–63 days, depending upon incubation temperature. Hatchlings average about 30 mm (1.2 inches) in snout-vent length. They grow rapidly and reach sexual maturity in their second summer. COMMENTS AND CONSERVATION Th rough hybridization, the Sixlined Racerunner has made genetic contributions to the Laredo Striped Whiptail (Aspidoscelis laredoensis). This species is locally abundant, particularly in sandy areas and in open prairies. It is on the TPWD’s White List, which allows it to be collected for commercial purposes. Most specimens entering the commercial trade are undoubtedly sold as food for lizard-eating snakes.

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Gray Checkered Whiptail

Gray Checkered Whiptail

Aspidoscelis dixoni (Scudday, 1973) Unisexual species

SIZE Snout-vent length may be up to 108 mm (4.25 inches), with a total length of up to 318 mm (12.5 inches). DESCRIPTION Mature individuals are well marked with a fi ne checkering of dark squares and rectangles on a light ground color. Striping or vestiges of striping may be present on the nape and back. The ground coloration is typically gray or whitish on the anterior part of the body, shading to a rusty coloration at midbody and on the hips. The tail is essentially patternless and may be rusty at the base, but dulls toward the tip. Ventrally, the throat may be light tan, and the belly is whitish. Dorsally, hatch-

Gray Checkered Whiptail, Presidio County, Texas. 26 9

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lings have a pattern of 10–14 light lines on a dark field with spots. As the lizard ages, the spots fuse with the light lines, resulting in the subdivision of the dark ground into the small squares and rectangles that constitute the adults’ checkered patterns. SIMILAR SPECIES The Common Checkered Whiptail (Aspidoscelis tesselata) has larger, more distinct checkering and reaches a slightly larger size. The Marbled Whiptail (Aspidoscelis marmorata) may be even more finely marked with checkering than the Gray Checkered Whiptail, but has a ground color that is gray or tan, the dark markings being typically of a slightly darker shade of brown rather than distinctly black on a light ground color. The Rusty-rumped Whiptail (Aspidoscelis septemvittata) is more distinctly striped at all ages and may have blue coloration on the forelimbs and tail. The latter 2 species are sexual species and include males in their populations. All other whiptails that occur with the Gray Checkered Whiptail have a pattern of light lines on dark fields (with or without light spots in those fields). DISTRIBUTION In Texas, this species occurs in a very small area on the slopes of the Chinati Mountains in Presidio County. One other population is known from Antelope Pass in the Peloncillo Mountains of Hidalgo County, New Mexico. NATURAL HISTORY In Texas, this species occupies sparsely vegetated, gravelly slopes, washes, and canyons adjacent to and extending into the lower slopes of the Chinati Mountains. Soils in this area are of volcanic origin and consist of ash deposits, decomposed volcanic gravels, and rocks originating from rhyolites and basalts present in the Chinati Mountains. Vegetation includes creosote bushes, lechuguilla, cacti, ocotillos, acacias, mesquites, and grasses. This species is a more deliberate forager than most other whiptails, and may be more approachable. Like other whiptails, it forages actively, probing and scraping through gravel and detritus in search of insect prey. Termites appear to be a favored prey item, and ants, beetles, cockroaches, and flies, as well as arachnids such as spiders and solpugids, are also consumed. REPRODUCTION The Gray Checkered Whiptail is an all-female parthenogenetic species. The Texas population consists of 2 clonal lines (pattern classes A and B), each of which descends from a single ancestor. The members of each pattern class are essentially identical genetically to all other members of that pattern 270

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Gray Checkered Whiptail

class. Reproduction occurs from May through July; clutches contain 1–6 eggs. The details of this species’ reproductive behavior have not been documented in Texas, although it is assumed that individuals follow reproductive cycles similar to those seen in other parthenogenetic whiptails (see the discussion of parthenogenetic reproduction under the family account). Hatchlings emerge in August or September and average 34 mm (1.3 inches) in snout-vent length. They grow rapidly and may reproduce in their second summer. COMMENTS AND CONSERVATION Although this species is not officially listed as a threatened species in Texas, because of its extremely limited range in the state, it almost certainly should be so recognized. Declines have been documented for the population in southwestern New Mexico, where the species is considered endangered. Efforts should be taken to assess the status of this species in Texas to ensure its survival globally. The Gray Checkered Whiptail is a diploid, all-female parthenogenetic species that arose through hybridization between a male Rusty-rumped Whiptail (Aspidoscelis septemvittata) and a female Marbled Whiptail (Aspidoscelis marmorata). There are 3 pattern classes within this species, 2 of them in Texas and 1 in New Mexico. Each represents a separate clonal population and likely arose from separate hybridization events.

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Teiidae

Common Checkered Whiptail

Aspidoscelis tesselata (Say, in James, 1823) Unisexual species

SIZE Snout-vent length may be up to 106 mm (4.2 inches), with a total length of up to 394 mm (15.5 inches). DESCRIPTION The Common Checkered Whiptail is one of the largest and most distinctly marked members of the genus Aspidoscelis. The adult pattern is made up almost completely of bold, dark rectangles and checkers on a light ground color. Toward the hips, the ground color assumes a rusty cast, and this coloration extends onto the tail. Dark checkering is present also on at least the base of the tail. Only traces of light stripes are evident, primarily on the nape and upper back. Juveniles of this species are distinctly striped with 6–14 light lines, usually with obvious light spots occupying the dark fields between the stripes. The spots on the flanks usually fuse with the light lateral stripes at or just after hatching. As the lizard ages, the light spots increase in size, fusing with the dorsal stripes and causing the dark fields to break into the checkered pattern seen in adults. In smaller adults, traces of stripes may persist, particularly on the upper back and nape, while in older adults these traces may be lost entirely. SIMILAR SPECIES The Gray Checkered Whiptail (Aspidoscelis dixoni) is smaller overall and has smaller, less distinct checkering. The Marbled Whiptail (Aspidoscelis marmorata) may be even more finely marked with checkering than the Gray Checkered Whiptail, and has a ground color that is gray or tan with dark markings typically of a slightly darker shade of brown rather than distinctly black on a light ground color. The Rusty-rumped 272

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Common Checkered Whiptail

Common Checkered Whiptail, adult, Presidio County, Texas.

Whiptail (Aspidoscelis septemvittata) is more distinctly striped at all ages and may have blue coloration on the forelimbs and tail. The latter 2 species are sexual species and include males in their populations. All other whiptails that occur with the Common Checkered Whiptail have a pattern of light lines on dark fields (with or without light spots in those fields). DISTRIBUTION In Texas, this species occurs in 2 disjunct populations. The bulk of its range is in the Trans-Pecos and adjacent counties; a second population occurs in the Texas Panhandle. These 2 populations are not truly isolated, since the lizards occur throughout much of central New Mexico, thus connecting the Texas populations. Isolated populations are known from southeastern Colorado and western Oklahoma. In Mexico, it is known primarily from the canyons of the Rio Grande and a tributary, the Rio Conchos, in Chihuahua and Coahuila. NATURAL HISTORY The Common Checkered Whiptail occupies a wide range of habitats across its large range, primarily occupying sites with gravelly soils (although some sandy sites are occupied too). It can be found from piñon-juniper sites through grasslands and into creosote bush deserts. It may be particularly common along major rivers in riparian corridors, likely because of the increased availability of arthropod prey in those areas. As has been noted with several other all-female species, 273

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Teiidae

Common Checkered Whiptail, juvenile, Jeff Davis County, Texas.

it is more approachable than most other whiptail species, and its movements and foraging patterns are more deliberate. Foraging behavior is otherwise typical for a whiptail, involving searching through surface litter and detritus with the snout and forefeet until arthropod prey is located. As with many whiptail species, termites make up an important component of its diet. Other food items include beetles, ants, grasshoppers, caterpillars, and butterflies. It is active from April to October or November; younger individuals are active earlier and later in the year than adults. It may be active at body temperatures of up to 40°C (104°F). Activity may occur at midday in the spring and fall, but high temperatures during the summer frequently exceed this figure, so the lizards adopt a distinctly bimodal activity cycle, with activity occurring in the morning and the late afternoon. During the heat of midday, these lizards may retreat into dense shade or beneath the surface into burrows. REPRODUCTION Much of what is known about the reproductive biology of parthenogenetic whiptails was learned by studying populations of this species (along with the New Mexico Whiptail, Aspidoscelis neomexicana) in central New Mexico (see the discussion under the family account above for details of parthenogenetic reproduction). Several clonal lineages occur within this species, each the descendant of an original offspring that 274

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Common Checkered Whiptail

was produced by hybridization between 2 sexually reproducing species. Gravid females have been documented from May to July, and clutch sizes range from 1 to 8 eggs. Hatchlings emerge from late July through September and average 40 mm (1.6 inches) in snout-vent length. They grow rapidly and may reproduce in their second summer. COMMENTS AND CONSERVATION The Common Checkered Whiptail is a diploid, all-female, parthenogenetic species that arose through the hybridization of the Marbled Whiptail (Aspidoscelis marmorata) and the Rusty-rumped Whiptail (Aspidoscelis septemvittata). Several pattern classes of this species exist, each of which represent a different clonal lineage. Two of these have been elevated to full species status: the Gray Checkered Whiptail (Aspidoscelis dixoni) and the Colorado Checkered Whiptail (Aspidoscelis neotesselata), which is endemic to southeastern Colorado. The Common Checkered Whiptail is locally common in the Trans-Pecos and in the Texas Panhandle, but is typically outnumbered at any one location by whiptail species such as the Marbled Whiptail. The Common Checkered Whiptail is on the TPWD’s White List and so can be collected for commercial purposes. Like other whiptail species, it makes for a difficult captive, and so it is likely that most individuals entering the commercial trade are sold as food for lizard-eating snakes.

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Teiidae

Chihuahuan Spotted Whiptail

Aspidoscelis exsanguis (Lowe, 1956) Unisexual species

SIZE Snout-vent length may be up to 98 mm (3.9 inches), with a total length of up to 314 mm (12.4 inches). DESCRIPTION The Chihuahuan Spotted Whiptail has a combination of 6 light dorsal stripes and distinct spotting that is present in both the dark fields between the stripes as well as overlaying the stripes themselves. Juveniles and young adults are more distinctly striped than adults, with spots that are relatively faintly indicated. As the animal ages, the dark fields between the stripes lighten and the dorsal stripes fade in intensity as the spotting becomes more pronounced. The spots on the anterior portion of the body are typically white or cream, and those above the hips may be a rather bright yellowish color. Older adults may appear to be largely brownish with faint stripes and distinct spots. The throat and belly are pale gray or whitish. In juveniles, the tail may be bluish or green, while in most adults the tail is gray or grayish brown. SIMILAR SPECIES In Texas, the species most similar to the Chihuahuan Spotted Whiptail is the Texas Spotted Whiptail (Aspidoscelis gularis) and the New Mexico Whiptail (Aspidoscelis neomexicana). The Texas Spotted Whiptail is a sexual species; males can be readily distinguished by their pink to orange throats and blue-black chests and bellies. Female Texas Spotted Whiptails are more similar to Chihuahuan Spotted Whiptails, but typically have much more distinct stripes—usually 7 or 8 rather than 6, often with a greenish cast. The spots between the stripes are confined to the dark fields and are most evident 276

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Chihuahuan Spotted Whiptail

Chihuahuan Spotted Whiptail, Jeff Davis County, Texas.

on the lateral surfaces of the body. Furthermore, Texas Spotted Whiptails typically have reddish tails at all ages, particularly as juveniles, whereas Chihuahuan Spotted Whiptails have tails that are greenish olive or plain grayish brown. The New Mexico Whiptail shows much fainter spots in the dark fields, and the spots are confined to the dark fields. The New Mexico Whiptail also has a distinctly wavy middorsal stripe that is lacking in the Chihuahuan Spotted Whiptail. An occasional adult Chihuahuan Spotted Whiptail may not have distinct spots, and in that case it should be distinguished from the New Mexico Whiptail by careful examination of the supraorbital semicircles, which penetrate far forward between the supraorbital scales and the remaining head scales in that species. DISTRIBUTION In Texas, the Chihuahuan Spotted Whiptail occurs in all counties west of the Pecos River except Val Verde County. It ranges north through most of central and northern New Mexico and west into extreme eastern Arizona. In Mexico, it primarily occurs in Chihuahua, though there are records from extreme northeastern Sonora along the Mexican border with New Mexico and Arizona. NATURAL HISTORY Although the range of this species closely corresponds to the Chihuahuan Desert ecoregion, within this region it is most abundant in mid-elevation oak-juniper-piñon wood277

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Teiidae

Chihuahuan Spotted Whiptail, Brewster County, Texas.

lands in the mountains. It occurs also in desert grasslands as well as in rocky canyons and arroyos down into typical Chihuahuan Desert areas containing lechuguilla, ocotillo, and prickly pear cactus. It may be commonly encountered in dense brush in riparian corridors that meander through these regions. Th is species maintains its body temperature near 38°C (100°F), primarily through behavioral means. It seeks areas of shade when it becomes too hot, or sunny spots when it becomes too cool. At higher elevations, it may be active throughout the day, even during midsummer. At lower elevations, it frequently displays a bimodal activity pattern, retreating into underground shelters when midday temperatures become too extreme. It is surfaceactive from late April or May through October or November, depending on temperature and elevation. It is an active forager, nosing, scraping, and pawing through surface debris in search of insect and arthropod prey. Grasshoppers, termites, insect larvae, beetles, spiders, and scorpions have all been documented as prey items for this species. Chihuahuan Spotted Whiptails move with a jerky fashion typical of members of this genus, but like other parthenogenetic species often allow much closer approach than do their sexually reproducing relatives. REPRODUCTION As with other all-female, parthenogenetic species, the Chihuahuan Spotted Whiptail may engage in courtship and 278

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Chihuahuan Spotted Whiptail

pseudocopulation (see the discussion of these reproductive activities under the family account). Egg development begins in May, and most oviposition happens in June through August. From 1 to 6 eggs are laid underground, presumably in a burrow constructed by the female, and hatchlings emerge in 45–60 days, depending upon incubation temperatures. Hatchlings are about 36 mm (1.4 inches) in snout-vent length. They grow rapidly and may reproduce in their second summer. COMMENTS AND CONSERVATION The Chihuahuan Spotted Whiptail is a triploid (having 3 copies of each chromosome instead of the more typical 2), all-female, parthenogenetic species. It apparently arose through the hybridization of a male Texas Spotted Whiptail (Aspidoscelis gularis) with a presumably extinct diploid all-female lineage that arose through the hybridization of the Canyon Spotted Whiptail (Aspidoscelis burti) and the Little Striped Whiptail (Aspidoscelis inornata). Each species contributed a copy of its chromosome complement to the Chihuahuan Spotted Whiptail. Several pattern classes occur within this species; they vary somewhat in the intensity of the striping and degree of spotting. Each pattern class represents a separate clonal lineage that may have arisen from independent hybridization events. Furthermore, it has been suggested that the extinct parthenogenetic ancestor resulting from the hybridization of the Canyon Spotted and Little Striped Whiptails may be a common ancestor of both this species and the Desert Grassland Whiptail (Aspidoscelis uniparens). Although often quite abundant in its Trans-Pecos range, the Chihuahuan Spotted Whiptail is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Teiidae

New Mexico Whiptail

Aspidoscelis neomexicana (Lowe and Zweifel, 1952) Unisexual species

SIZE Snout-vent length may be up to 86 mm (3.4 inches), with a total length of up to 302 mm (11.9 inches). DESCRIPTION The New Mexico Whiptail is a striped and spotted species with 7 distinct dorsal stripes. Unique among Texas whiptail species, the middorsal stripe is distinctly wavy rather than straight. The spotting present in the dark fields between the stripes is most prominent in the lateral fields. The New Mexico Whiptail is also unique in that the supraorbital semicircles extend far forward between the supraorbital scales and

New Mexico Whiptail, San Miguel County, New Mexico. 280

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New Mexico Whiptail

New Mexico Whiptail, San Miguel County, New Mexico.

the remaining head scales, which doesn’t occur in other whiptail species. Juveniles are more distinctly striped than adults and mostly lack the spotting in the dark fields. The tail is distinctly greenish in juveniles and gray green in adults. SIMILAR SPECIES The New Mexico Whiptail is most similar to the Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis), which differs by having less distinct stripes, much more pronounced dorsal spotting, straight rather than wavy middorsal stripes, and supraorbital semicircles that do not extend forward between the supraorbital scales and the other head scales. The cooccurring Desert Grassland Whiptail (Aspidoscelis uniparens) is smaller, lacks spotting in the dark fields between the stripes, and has 6 dorsal stripes rather than 7. The Little-striped Whiptail (Aspidoscelis inornata), a sexual species, is smaller still, lacks spotting in the dark fields, and has blue on the throat, belly, and tail in both sexes (although it is more pronounced in males). DISTRIBUTION In Texas, this species occurs in extreme western Texas, primarily along the Rio Grande in El Paso, Hudspeth, Culberson, and Presidio Counties. It ranges north along the Rio Grande into northern New Mexico and west from El Paso almost to the Arizona state line. Several disjunct populations scattered from northeastern Arizona to northeastern New Mexico are likely due to introductions. In Mexico, this species is 281

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Teiidae

New Mexico Whiptail, El Paso County, Texas.

known only from the immediate vicinity of the Rio Grande Valley adjacent to Texas. NATURAL HISTORY The New Mexico Whiptail is active from April through October. It is an active forager and searches through surface detritus by nosing, poking, and scraping through such material with its nose and forelimbs. It preys primarily on a wide range of insects, including adults and larvae of butterflies, moths, beetles, grasshoppers, crickets, ants, and termites. At some times of the year, termites may be particularly important in the diet. It prefers sandy soils, particularly those in close association with the Rio Grande floodplain, where it digs burrows as much as 300 mm (11.8 inches) deep. The lizards retreat to these burrows to avoid the midday summer heat, and may plug the entrance to their burrows with dirt. They may overwinter in their burrows as well as lay eggs in them. They prefer to be active when ground temperatures are 26°C–30°C (79°F– 86°F). They retreat underground when surface temperatures exceed 50°C (122°F). In Texas, this species is found primarily along the Rio Grande corridor, where it occurs in both natural and disturbed agricultural areas. Natural vegetative associations include grasses, mesquites, creosote, and saltbrush. REPRODUCTION Th is is an all-female, parthenogenetic species that reproduces asexually. Like most other parthenogenetic species, 282

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New Mexico Whiptail

it engages in pseudocopulation and courtship behavior to stimulate egg production (see the discussion under the family account for details of this process). Females lay clutches of 2 eggs from June through August, up to 2 clutches a season. Eggs are laid in burrows, typically constructed by the egg-laying females themselves. Hatchlings emerge in 45–60 days, length of incubation varying with temperature. Hatchlings average 36 mm (1.4  inches) in snout-vent length. They grow rapidly and may reach sexual maturity in their second summer. COMMENTS AND CONSERVATION The New Mexico Whiptail is a diploid, parthenogenetic, all-female species that arose through the hybridization of a male Marbled Whiptail (Aspidoscelis marmorata) and a female Little Striped Whiptail (Aspidoscelis inornata). This species has a rather limited range in Texas, being restricted mostly to the immediate vicinity of the Rio Grande in extreme western Texas. It may be locally common, particularly in riparian situations. This species is on the TPWD’s Black List and so may not be collected for commercial purposes.

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Teiidae

Desert Grassland Whiptail

Aspidoscelis uniparens (Wright and Lowe, 1965) Unisexual species

SIZE Snout-vent length may be up to 74 mm (2.9 inches), with a total length of up to 238 mm (9.4 inches). DESCRIPTION The Desert Grassland Whiptail is a medium-sized whiptail with 6 light dorsal stripes and unspotted dark fields between the stripes. The dorsal stripes may be whitish or yellowish. Some individuals may show a trace of a seventh light stripe on the nape. Ventral surfaces are typically an unmarked whitish color—in some specimens, a faint bluish tint may be present, but never so prominently as is seen in the Little Striped Whiptail (Aspidoscelis inornata). The base of the tail is gray or brown, gradually turning greenish toward the tip. It has an enlarged patch of scales on its forelimbs as well as an enlarged row of scales just anterior to the gular fold on the throat. The young are more distinctly marked than adults, with brighter stripes and darker fields between them, but are otherwise similarly patterned. SIMILAR SPECIES The Desert Grassland Whiptail is most similar in overall appearance to the Little Striped Whiptail (Aspidoscelis inornata). The Little Striped Whiptail is a sexual species that includes males in its population, has 7 light dorsal stripes rather than 6, lacks enlarged scales on its forelimbs and at its gular fold, and has a bluish rather than a greenish tail. Most specimens also exhibit a bluish tint on the throat and belly— a coloration that is particularly intense in males. The Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis) and New Mexico Whiptail (Aspidoscelis neomexicana) have light spots in the 28 4

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Desert Grassland Whiptail

Desert Grassland Whiptail, Cochise County, Arizona.

dark fields between their stripes, reach larger adult sizes, and lack the enlarged forelimb and gular-fold scales. DISTRIBUTION In Texas, the Desert Grassland Whiptail is restricted to El Paso County. It ranges north into central New Mexico along the Rio Grande and west into western Arizona along the lower slopes of the Mogollon Rim. In Mexico, it occurs south into central Chihuahua and west into extreme northern Sonora along the Arizona border. NATURAL HISTORY As its name implies, this species prefers grassy habitats in arid and semiarid areas. It may be found in association with mesquites and yuccas but is not common in areas where brush encroachment has eliminated natural grass cover. It may also range into oak-juniper-piñon woodlands on the lower slopes of mountains, ascend into otherwise mountainous areas along grassy river valleys, or descend into true desert areas along the riparian corridors associated with major rivers. It may be active from March until late October. In the spring and fall, this species may be active all day. In the heat of summer, activity is restricted to morning and late afternoon; the animals retreat into their burrows to avoid the midday heat. The diet of this species has not been well studied, but termites may make up a significant portion of it. The lizard forages in typical whiptail fashion, probing and scraping at surface detritus in search of ar285

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Teiidae

Desert Grassland Whiptail, Cochise County, Arizona.

thropod prey. Although it is less wary and less difficult to approach than most sexually reproducing species, it is warier than most other unisexual species. REPRODUCTION The Desert Grassland Whiptail is a typical parthenogenetic whiptail species in which all members of the population are females that produce viable eggs without fertilization by sperm. Like other parthenogenetic species, females engage in pseudocopulatory and courtship behaviors, presumably to stimulate egg production (see the discussion under the family account). Females lay clutches of 1–4 eggs, usually in late spring or early summer, in underground burrows. The eggs incubate for 45–60 days, depending upon temperature. Hatchlings emerge in late summer or early fall and average 36 mm (1.8 inches) in snout-vent length. They grow rapidly and reproduce in their second summer. COMMENTS AND CONSERVATION The Desert Grassland Whiptail is a triploid, all-female, parthenogenetic species that arose from a two-stage hybridization process. The initial hybridization event involved the Canyon Spotted Whiptail (Aspidoscelis burti) and the Little Striped Whiptail (Aspidoscelis inornata), which produced a presumably extinct parthenogenetic species. That form then hybridized with a male Little Striped Whiptail, resulting in the populations known today as the Desert Grassland Whip286

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Desert Grassland Whiptail

tail. Being a triploid species, it has 3 copies of each of its chromosomes, 1 copy from the Canyon Spotted Whiptail and 2 copies from the Little Striped Whiptail. Considerable variation among populations of the Desert Grassland Whiptail suggests that it may have originated from more than a single hybridization event. Furthermore, it has been suggested that the extinct parthenogenetic ancestor resulting from the hybridization of the Canyon Spotted Whiptail and Little Striped Whiptail may be a common ancestor also to the Chihuahuan Spotted Whiptail (Aspidoscelis exsanguis). The Desert Grassland Whiptail has a very limited distribution in Texas and is rarely encountered. It is on the TPWD’s Black List and so cannot be collected for commercial purposes.

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Teiidae

Laredo Striped Whiptail

Aspidoscelis laredoensis (McKinney, Kay, and Anderson, 1973) Unisexual species

SIZE Snout-vent length may be up to 90 mm (3.5 inches), with a total length of up to 289 mm (11.4 inches). DESCRIPTION The Laredo Striped Whiptail has 7 distinct light yellow to greenish-yellow dorsal stripes. The middorsal stripe is noticeably narrower than the remaining stripes. The fields between the stripes are dark brown, and the lateral fields may have faint light spots in some individuals. The tail is brown or gray and may have a greenish tint, particularly toward the tip. The dorsal surfaces of the hind limbs are noticeably patterned with a series of dark reticulations. Hatchlings and young individuals are more boldly marked than adults, with brighter stripes and darker fields between them. SIMILAR SPECIES The Laredo Striped Whiptail is most similar to the Texas Spotted Whiptail (Aspidoscelis gularis). Males of the latter species are easily distinguished by their pink or orange throats and blue-black chests and bellies; females have more pronounced spots in the dark fields and a much wider middorsal stripe, lack the prominently reticulated hind limbs, and often have reddish tails. The Six-lined Racerunner (Aspidoscelis sexlineata) is typically bright greenish anteriorly, and the Little Striped Whiptail (Aspidoscelis inornata) has a blue throat, belly, and tail. DISTRIBUTION Once thought to be restricted to the immediate vicinity of Laredo, this species is now known to occur from Del Rio to the mouth of the Rio Grande, southeast of Brownsville,

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Laredo Striped Whiptail

Laredo Striped Whiptail, Zapata County, Texas.

primarily within a few miles of the river itself (although records exist from Dimmitt and LaSalle Counties). In Mexico, it presumably occurs along the Rio Grande in the states of Coahuila, Nuevo Leon, and Tamaulipas. NATURAL HISTORY The Laredo Striped Whiptail primarily occupies open and semiopen brushland dominated by mesquites and acacias interspersed with open areas. Soils are sandy and gravelly. It may be found surface-active from March through November. Like other whiptails, it feeds primarily on insects and other small arthropods, for which it searches by actively probing, digging, and scraping through surface debris with its snout and forelimbs. REPRODUCTION The Laredo Striped Whiptail is an all-female parthenogenetic species that reproduces through the production of viable eggs without fertilization by sperm. Members of the species presumably engage in courtship and pseudocopulation like other parthenogenetic whiptails (see the discussion under the family account for details of this process). Oviposition occurs beginning in May, and some females may lay multiple clutches of 1–4 eggs in a single season. Eggs are laid in burrows constructed by the female and take 48–58 days to incubate (depending upon temperature). Hatchlings are about 35 mm (1.4 inches) 289

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Teiidae

in snout-vent length, grow rapidly, and reach sexual maturity in their second summer. Some evidence shows that most individuals don’t survive to see a third summer, resulting in a nearly annual life cycle for the species. COMMENTS AND CONSERVATION The Laredo Striped Whiptail is a diploid, all-female, parthenogenetic species that arose through the hybridization of a female Texas Spotted Whiptail (Aspidoscelis gularis) and a male Six-lined Racerunner (Aspidoscelis sexlineata). At least 2 pattern classes (designated A and B), which represent different clonal lineages, have arisen through different hybridization events. This species was first described to science in 1973. It may be locally common along the Rio Grande in southwestern Texas, but is usually outnumbered by the Texas Spotted Whiptail. It is on the TPWD’s Black List and therefore cannot be collected for commercial purposes.

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Diploglossa

INFRAORDER DIPLOGLOSSA

The infraorder Diploglossa includes 127 species in 3 families. The Anniellidae includes 2 species of small, fossorial, short-tailed, legless lizards that occur in California and Baja California. The Xenosauridae consists of 6 species of knob-scaled, crevicedwelling lizards that occur in Mexico and Central America. The remaining 119 species are grouped together into the family Anguidae, and include both tropical and temperate alligator lizards and glass lizards.

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Anguidae

FAMILY ANGUIDAE

The family Anguidae consists of 119 species of alligator lizards and glass lizards distributed across Europe, Asia, the Caribbean, and South, Central, and North America. They are characterized by a forked, snakelike tongue that is used as a chemosensory organ, hard rectangular body scales supported by osteoderms, and a distinct lateral fold interrupting the armored skin, allowing for expansion of the torso during breathing, when engorged with food, or when (in females) carrying eggs. In North America, anguids are divided into 2 groups, the alligator lizards and the glass lizards. The 2 genera of North American alligator lizards (Elgaria and Gerrhonotus) are short-limbed, slender animals with long tails and triangular, pointed, “alligator-like” snouts. The glass lizards (genus Ophisaurus) are legless and have exceptionally long tails. In most species of glass lizards, the tails are exceedingly fragile and may be autotomized when threatened by a predator, in some cases even without direct contact with the tail. Of the 5 U.S. species of alligator lizards, which have a primarily western distribution, 1 occurs in Texas. Of the 4 U.S. species of glass lizards, which have a primarily southeastern distribution, 1 reaches the western limits of its distribution in Texas.

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Texas Alligator Lizard

Texas Alligator Lizard

Gerrhonotus infernalis Baird, 1859 “1858”

SIZE Snout-vent length may be up to 203 mm (8 inches), with a total length of up to 508 mm (20 inches). Males are larger than females. DESCRIPTION Adults are large slender lizards with distinctly pointed, “alligator-like” heads. They have short limbs and extremely long, prehensile tails. Each body scale is rectangular and underlain with bone, giving the skin a rigid, armored texture. The sides of the body are marked by a lengthwise lateral fold that extends from the back of the head to the hind limbs. The scales inside the lateral fold are small and pebble like. The lateral

Texas Alligator Lizard, male, Val Verde County, Texas. 293

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Anguidae

Texas Alligator Lizard, head detail, male, Val Verde County, Texas.

Texas Alligator Lizard, female, Kerr County, Texas.

fold allows the otherwise armored body of these lizards to expand while breathing, when engorged with food, or when (if female) carrying eggs. Their ground color ranges from a tannish gray to a rich brown; 7–10 irregular light body bands consisting of whitish individual scales loosely outline darker brownish pigment. These bands continue onto the tail. Adults rarely have intact, unregenerated tails, and regenerated portions of tails are 29 4

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Texas Alligator Lizard

patternless. Males have distinctly longer, wider heads than females, and females have proportionally longer bodies. The pattern of hatchlings is quite different, with a dark brown ground color interspersed with light bands. As hatchlings mature, the dark pigment fades; by their first fall, juveniles are nearly patternless, with faint vestiges of the light adult bands present— typically without the dark scale borders present in adults. SIMILAR SPECIES No other lizard in Texas is remotely similar to the Texas Alligator Lizard. From a distance, they may be confused with a large skink such as the Great Plains Skink (Plestiodon obsoletus), but that species has smooth, cycloid scales and a pattern of dark streaks arranged in rows. DISTRIBUTION In Texas, this species ranges from the Chisos Mountains in Brewster County east through the Stockton Plateau (in Val Verde County) across the Balcones Escarpment to Bexar County and north to Williamson and San Saba Counties. An isolated record is known from Fayette County along the Colorado River. In Mexico, it ranges south through the mountains of Coahuila, Nuevo Leon, Tamaulipas, and San Luis Potosí, with isolated records in the mountains of Durango and Chihuahua. NATURAL HISTORY The Texas Alligator Lizard may be found surface-active year-round, emerging from hibernacula to bask on sunny winter days. Its primary activity season is bimodal, with a spring activity period from March through May, and a fall activity period from late September through November. During the warmest summer months, it typically retreats to avoid heat and drought, but if temperatures remain moderate and rainfall is ample, it may be active throughout the summer. At higher elevations, as in the Chisos Mountains of the TransPecos, its peak activity may coincide with monsoonal summer rainfall. Although primarily diurnal, it may occasionally be encountered nocturnally, especially during the early summer. It prefers shady, wooded canyons with rocky exposures in which to hibernate. During the winter, it can be found basking on exposed rock ledges; during the warmer months it is most frequently encountered in shady areas. It has distinct arboreal tendencies, and its strongly prehensile tail can be used to grasp branches as it climbs about through bushes and trees. Where it ranges into open areas of the Chihuahuan Desert, it is invariably associated with sheltered canyons, where it adopts a dis295

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Texas Alligator Lizard, male, Real County, Texas.

tinctly crepuscular habit, foraging along shaded rock ledges. These lizards are insectivores that search for prey by slowly and deliberately moving through their habitat, occasionally flicking their forked tongues to detect chemical cues left behind by their prey. Once a prey item is detected, the lizards slowly and deliberately approach to within striking distance, at which point they lunge to grasp the prey. Prey items include spiders, scorpions, grasshoppers, crickets, beetles, and other invertebrates. In captivity they have been known to feed upon small vertebrates, including other lizards. Texas Alligator Lizards are most common in wooded canyons, both on the Balcones Escarpment and in the Chisos Mountains. They occur in low population densities in desert canyons on the Stockton Plateau. REPRODUCTION Breeding occurs in the fall, typically in October and into November. Foraging females apparently leave pheromone trails that males detect by smell and then follow. Upon encountering a female, a male may court her for hours before copulation. If 2 males encounter each other, they may engage in combat. During the breeding season, males seen searching for females outnumber observed females by about 4 to 1. Egg development is delayed during hibernation, and eggs are laid between February and June, depending more upon seasonal factors than upon the timing of reproduction. High-elevation 29 6

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Texas Alligator Lizard

populations lay clutches later in the season than those at lower elevations. Clutches contain 5–31 eggs, with larger females having larger clutches. Females attend and presumably guard their clutches throughout the incubation period, which may last 32– 62 days (depending upon temperature). Typically, only a single clutch of eggs is laid annually; a second clutch may be laid in years when food supplies are exceptionally plentiful. Hatchlings

Texas Alligator Lizard, hatchling, Edwards County, Texas.

Texas Alligator Lizard, juvenile, Real County, Texas. 297

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Anguidae

average 95 mm (3.75 inches) in total length. They grow rapidly, and by fall may measure as much as 200 mm (8 inches) in total length. Sexual maturity is likely not reached until the lizards are 2 years old. COMMENTS AND CONSERVATION The Texas Alligator Lizard is one of the most sought-after species of lizard in the state by amateur herpetologists, owing to its fascinating appearance and its reclusive habits. Populations in some areas are threatened by urban sprawl, but it may persist in larger parks and green spaces if these areas retain access to rocky canyons and outcrops. It is on the TPWD’s White List and so may be collected for commercial purposes. The captive care of this species is rather straightforward. They require large cages that include shelter and branches into which they may climb. Vitamin supplementation, particularly with calcium and D3, is necessary to ensure skeletal health. Ultraviolet lighting is desirable but not required. Hatchlings and juveniles are extremely susceptible to skeletal disorders resulting from a lack of calcium, D3, and UV lighting, and it is believed that the care requirements of hatchlings and juveniles are more complex. Several breeders who have bred this species in years past have abandoned their efforts because of difficulty in surmounting these obstacles. Furthermore, the lizards are rather shy and reclusive and do not do well when housed with more aggressive species. In the older literature, this species was considered to be conspecific with the Mexican species Gerrhonotus liocephalus. Some authorities consider populations of this species that occur in Durango and Chihuahua to represent a third species, Gerrhonotus taylori.

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Slender Glass Lizard

Slender Glass Lizard

Ophisaurus attenuatus Cope, 1880

SIZE Snout-vent length may be up to 289 mm (11.4 inches), with a total length of up to 1,067 mm (42 inches). Males and females are similarly sized. DESCRIPTION The Slender Glass Lizard has stiff, platelike body scales, each of which is supported by a bony dermal plate called an osteoderm. This makes the body rigid and stiff. This armoring is relieved by a lateral fold running from the back of the head to the end of the body, which allows the body to expand while breathing, when engorged with food, or when (if female) gravid with eggs. The snout is rather pointed, and the head is not distinct from the body. The tail is long, more than twice the

Slender Glass Lizard, male, Jasper County, Texas.

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Slender Glass Lizard, female, Jasper County, Texas.

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length of the body when unregenerated. The tail is easily broken, having notably fragile fracture planes in each of the caudal vertebrae. The body’s ground color is a rich bronze marked with a series of stripes, including a broad, dark middorsal stripe; equally broad, paired dorsolateral stripes; and 4 or 5 thinner lateral stripes both above and below the lateral fold. These stripes extend from the back of the head to near the tip of an unregenerated tail. The regenerated portion of a tail is largely unmarked. In older individuals, particularly older males, the head, neck, and forebody may become increasingly marked with transverse dark-bordered white flecks and bars. SIMILAR SPECIES No other Texas lizard is remotely similar to the Slender Glass Lizard, although 3 other confusingly similar species occur on the southeastern coastal plains east of the Mississippi River. Slender Glass Lizards are most often confused with snakes, but unlike snakes, they have moveable eyelids, external ear openings, lateral body folds, and bodies less than half the length of their tails. Most snake species have broad, strap-like ventral scales rather than numerous platelike body scales on their undersides. Snakes have much suppler and more flexible bodies than the stiffly armored Slender Glass Lizards do. DISTRIBUTION The Slender Glass Lizard ranges throughout most of the eastern half of Texas—primarily east of a line from Hutchinson and Collingsworth Counties in the Texas Pan-

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Slender Glass Lizard

Slender Glass Lizard, old male, Morris County, Texas.

handle south through Eastland and Brown Counties in the Rolling Plains to Kerr and Bexar Counties in the Edwards Plateau to Jim Wells and Hidalgo Counties along the Texas Coastal Plain. Beyond Texas, it ranges north through Oklahoma and Kansas to southeastern Nebraska, southern Iowa, and Wisconsin, and east in prairie remnants in Illinois and Indiana. It ranges throughout most of Tennessee, central Kentucky, and along the coastal plains of North Carolina and Virginia, south to Florida and west to Mississippi and Louisiana. It is absent from the floodplain of the Mississippi River. Although its range closely approaches the Rio Grande in South Texas, it has not been documented in Mexico, though it could be expected to occur there along the Gulf Coast. NATURAL HISTORY Although capable of burrowing to seek refuge beneath cover objects, the Slender Glass Lizard is a “grass swimming” lizard rather than a burrower; the loss of limbs represents an adaptation for rapid movement through areas of dense grass. Consequently, the lizards are most abundant in natural grassy areas ranging from the understory of longleaf pine forests in Deep East Texas to the Coastal Prairies of the Texas Coast and the Rolling Plains of north-central Texas. Although primarily an insectivore, feeding on a variety of insects and similar arthropods, it also feeds on vertebrate prey, including small mammals, other lizards, and small snakes. The Slender Glass Lizard

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3 02

is primarily diurnal, but may occasionally be encountered at or shortly after dusk as it crosses lightly travelled roads. When grasped, this species may thrash about vigorously, and the tail may break even when the body is fully supported and the tail does not come into contact with any object. A broken tail continues to writhe about and may continue to break into smaller pieces as it comes into contact with surface objects such as sticks or bushes. Each broken tail part continues to wriggle long after it has been separated from the lizard’s body, presumably serving as a distraction to potential predators. REPRODUCTION Courtship and mating occur in the spring; 5– 20 eggs are laid in May or June. Eggs are typically laid in a depression beneath a cover object such as a board, rock, or log on the ground surface. Eggs may be laid also in the abandoned tunnels of small mammals. Females attend their nests throughout the incubation period and can raise egg temperatures by as much as 1.5°C above the ambient temperature. Unlike its close relative the Texas Alligator Lizard (Gerrhonotus infernalis), it does not bite in defense of its nest. Eggs hatch after an incubation period of 48–65 days. Hatchlings measure about 130 mm (5 inches) in total length. COMMENTS AND CONSERVATION The Slender Glass Lizard is a somewhat secretive and rarely encountered species that is most common in sandy prairie regions, both on the open plains and in wooded savannahs. Although it is believed to remain fairly abundant, much of its native range has been converted to agriculture or silviculture, likely reducing its populations severely. Furthermore, fire suppression in East Texas forests has resulted in a shift from open understories beneath pine and hardwood canopies to brush and leaf-litter-encroached thickets, which do not support healthy populations of this species. A distributional hiatus in this species’ range at the Mississippi River corresponds to the 2 currently named subspecies: the Western Slender Glass Lizard (Ophisaurus attenuatus attenuatus) occurs west of this gap, and the Eastern Slender Glass Lizard (Ophisaurus attenuatus longicaudus) occurs east of this break. Some have speculated that these 2 forms may represent distinct species. The Slender Glass Lizard is on the TPWD’s Black List and so may not be collected for commercial purposes. Glass lizards may make suitable captives for experienced keepers, but they are extremely sensitive to dehydration and dietary and vitamin deficiencies.

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APPENDIX A Species with Texas Records of Questionable Origin Gila Monster

Heloderma suspectum Cope, 1869 One old record for El Paso exists for this species. Rather than representing an actual locality for this species, it is believed that El Paso was a shipping point recorded for a specimen originating elsewhere in the Southwest. The nearest confirmed populations of this species occur in southwestern New Mexico in Grant and Hidalgo Counties; a small population is thought to occur in Luna County at Rattlesnake Mountain west of Deming; there also exists an extant record of a specimen collected at Kilbourne Hole in Doña Ana County, New Mexico, approximately 30 miles west of the Texas state line. That record is believed to represent a deliberately translocated or released captive individual. The bulk of this species’ range occurs in Arizona, extreme southwestern Utah, extreme southern Nevada, southeastern California, and south into the Mexican state of Sonora. The Gila Monster is the largest lizard native to the United States, 303

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Appendix A

Gila Monster, adult, Cochise County, Arizona.

reaching 360 mm (14 inches) in snout-vent length, and 570 mm (22 inches) in total length. Unlike most native lizards, its body is very stout, with powerful legs and a thick, fat-storing tail. It is also 1 of only 2 truly venomous lizards in the world, and the only venomous species to occur in the United States. Its body is covered with numerous bead-like or pebble-like scales. The blunt snout and feet are black, the body predominantly pinkish or orange with 4–5 distinct saddle-like black crossbands on the body and 3 more on the tail. In populations closest to Texas, these crossbands become interconnected and obscured by dark reticulations in adults.

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APPENDIX B Nonestablished Exotic Species Green Iguana

Iguana iguana (Linnaeus, 1758) The Green Iguana is a staple of the reptile pet trade, and many thousands of juvenile and hatchling Green Iguanas are sold at pet stores each year. The majority of these animals fare poorly, largely from the inexperience of their keepers. Individuals turn up on reptile rescue calls each year, most of which represent either deliberate releases or escapees. Although the lizard has been anecdotally reported as occurring in the Lower Rio Grande Valley of Texas, these reports are not supported by specimens or photos of wild individuals, and no reproducing populations are believed to have become established in Texas. Although this species has become established in subtropical regions of southern Florida, generally speaking, these tropical lizards cannot survive most Texas winters. Green Iguanas occur naturally in tropical regions of Mexico as well as throughout much of Central and South America. Although adults may reach 1,830 mm (72 inches) in total length, most individuals encountered are

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Appendix B

Green Iguana, juvenile, Amazonas, Brazil.

far smaller. Juveniles of most populations are richly colored in green with faintly indicated crossbars on the body. Adults are paler, and may be marked with orange, particularly on the head and neck of reproductive males. A raised crest of dorsal spines runs from the nape of the neck to the tip of the tail. A dewlap is present under the throat. The head is blunt, the legs are powerful, and the tail is long. Inland Bearded Dragon

Pogona vitticeps (Ahl, 1926)

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The Inland Bearded Dragon is another staple of the reptile pet trade, and large numbers of individuals are bred annually by herpetoculturalists across the United States. They occur in a bewildering variety of “designer” color morphs that are products of selective breeding for different colors and patterns. Because they are so commonly kept as pets, individuals occasionally escape and turn up on reptile rescue calls. The Inland Bearded Dragon is a large, somewhat spiny lizard with a wide head distinct from its neck, powerful limbs, and a short tail. Adults average about 200 mm (8 inches) in snout-vent length. The bodies of most individuals are tan or brown, but selectively bred individuals may show brighter colors, including yellow, orange, or red. Although the climatic conditions in its native Australian

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Appendix B

range are similar to some of the warmer and more arid regions of Texas, no populations are known to have become established. Tokay Gecko

Gekko gecko (Linnaeus, 1758) The Tokay Gecko is a large blue-gray gecko liberally marked with orange or reddish-brown spots. The body is covered with

Inland Bearded Dragon, male, captive specimen.

Tokay Gecko, Thailand. Photo by Kevin Messenger.

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Appendix B

distinct tubercles. The head is quite large and distinct from the neck; otherwise, it is proportionally very similar to the Mediterranean Gecko (Hemidactylus turcicus), only much larger, reaching 300 mm (12 inches) in total length. Th is species is occasionally seen in the pet trade, and it has anecdotally been reported from the Lower Rio Grande Valley in Cameron County. It is not known whether reproducing populations of this species have become established. Although it is unlikely that this tropical species can withstand Texas winters north of extreme South Texas, deliberate introductions of this species should not be attempted, since it is a voracious predator on other lizard species.

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APPENDIX C Lizard Informational Resources Texas is a great place to live for anyone interested in lizards. Readers who would like to get to know other people interested in lizards should contact some of the societies established just for that purpose. TEX AS SOCIETIES

Herpetological societies offer those interested in reptiles and amphibians a venue in which to interact with others who share their interests as well as to further their knowledge of these fascinating animals. Texas Herpetological Society East Texas Herpetological Society Austin Herpetological Society Brazos Valley Herpetological Society Dallas/Fort Worth Herpetological Society South Texas Herpetology Association West Texas Herpetological Society INTERNATIONAL U.S.-BASED SOCIETIES

Most international societies focus on conservation or on scientific research involving reptiles and amphibians, and thus are often considered professional organizations.

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Appendix C

Horned Lizard Conservation Society American Society of Ichthyologists and Herpetologists (ASIH), publisher of the journal Copeia Herpetologists’ League (HL), publisher of the journals Herpetologica and Herpetological Monographs Society for the Study of Amphibians and Reptiles (SSAR), publisher of the journals Herpetological Review, Journal of Herpetology, and Catalogue of American Amphibians and Reptiles Partners in Amphibian and Reptile Conservation (PARC) TEX AS MUSEUMS

The following research museums maintain collections of reptile and amphibian specimens that serve as a physical record of the history and distribution of reptile and amphibian species in the state. These specimens are often lent to researchers across the country for use in research projects. Biodiversity Research and Teaching Collections (BRTC) at Texas A&M University, long known as the Texas Cooperative Wildlife Collection (TCWC) Texas Natural Science Center (TNSC) at the University of Texas at Austin Amphibian and Reptile Diversity Research Center at the University of Texas at Arlington WEBSITES

Trying to distinguish Internet sites that provide accurate information from those that are suspect presents a daunting challenge. The following sites are associated with and maintained by professional herpetologists. The Reptile Database (www.reptile-database.org). Its work is supported by the European Molecular Biology Laboratory (EMBL), Heidelberg, Germany. Animal Diversity Web (http://animaldiversity.org). Its work is supported by the National Science Foundation. Herps of Texas (www.herpsoftexas.org). This work was originally supported by the Natural Science Center at the University of Texas at Austin. CITIZEN SCIENCE PROJECTS

In recent years, wildlife agencies across the country have established citizen science projects in order to take advantage of the vast resource 310

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Appendix C

represented by private citizens. The BRTC (TCWC), TNHC, and TPWD have started a Web-based vouchering system with photographs taken by the public. Observations can be uploaded to the Herps of Texas project (www.inaturalist.org/projects/herps-of-texas) and then used to help determine current distributions of Texas lizards.

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APPENDIX D Map of Texas Counties

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Appendix D

Figure 2. Texas Map with Counties. 314

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GLOSSARY ADPRESSED LIMBS Limbs of the animal pressed parallel to the sides of

the body. Forelimbs are laid backward along the body, and hind limbs are brought forward, with all limbs fully extended. The degree of overlap between limbs when adpressed may aid in identification. ALL ANTOIS A membrane in the amniotic egg that contains metabolic wastes produced by the developing embryo. AMNION A membrane in the amniotic egg that encloses and protects the developing embryo. AMNIOTIC EGG A shelled egg containing the following internal membranes surrounding the embryo: amnion, chorion, allantois, and yolk sac. AMPHISBAENIAN Burrowing squamates variously regarded as close lizard relatives or as highly specialized lizards. They typically have very short tails, either lack eyes or have small, nonfocusing eyes embedded within the skin, and have scales arranged as annuli encircling the body. ANTERIOR Pertaining to the head or forward part of the animal. ARBOREAL Living in trees. AUTOTOMY Self-amputation, as of the tail. BONY SPINE A row of bony masses covered with skin, immediately behind the head of some lizards. 317

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Glossary

BRUMATION A period of dormancy in ectotherms that is similar to hibernation, but involves different metabolic processes. True hibernation, seen in endotherms, involves a deliberate lowering of the body temperature through metabolic means. Brumation in ectotherms is a more passive process, involving a lowering of the body’s temperature as environmental temperatures decrease. CARRYING CAPACITY The number of organisms of a population, species, or community that can be supported by a particular area or ecosystem. CAUDAL Pertaining to the tail. CHELONIA The class that includes the turtles. CHORION A membrane in the amniotic egg that lies directly beneath the eggshell and allows for the exchange of respiratory gases between the embryo and the outside environment. CLIMATE CHANGE A global phenomenon resulting from the complex interactions of both natural and human-mediated processes, including pollution by greenhouse gases as well as habitat-altering processes such as deforestation, brush encroachment, and desertification. CLOACA (PLURAL: CLOACAE) In reptiles and amphibians, the common channel into which the digestive, urinary, and reproductive tracts discharge their contents. COMMUNIT Y All the species that occur in the same place at the same time. COMPETITIVE EXCLUSION A phenomenon that occurs when competing species cause other species not to fully occupy or exploit their natural habitat. CONSPECIFIC Of the same species. COPUL ATION In lizards, a sexual process in which the male of the species inserts a copulatory organ (the hemipenis) into the female’s cloaca in order to deliver sperm. CREPUSCUL AR Active during twilight, that is, at dawn and dusk. CREST An elevated section on the head or back. CROCODILIA The class that includes the crocodiles and alligators. DESERT GRASSL AND A semiarid land area covered in grasses that receives slightly more than 25 cm (10 in.) of rainfall annually. DESERTIFICATION Environmental changes resulting in the alteration of grasslands and desert-grasslands into more desert-like conditions, typically resulting from overgrazing, fire suppression, and groundwater depletion. DESICCATION The process of becoming extremely dry. DETRITUS Leaf litter and other dead organic matter intermixed with soil. DEWL AP A vertical, laterally compressed fold of extendable skin on the throat of some lizards. 318

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Glossary

DIGIT A toe or fi nger. DIL ATED Widened or expanded. DIPLOID Having the usual 2 sets of chromosomes. DIURNAL Active during daylight hours. DORSOL ATERAL Along the sides of the back. DORSOVENTRALLY FL ATTENED Flattened in such a way that the dor-

sal and ventral surfaces are wider than the lateral surfaces, that is, like a pancake. DORSUM The upper surface of an organism. ECOSYSTEM A community of living organisms in conjunction with the abiotic components of their environment. ECTOTHERM An organism dependent on an external heat source to warm its body. EGGS An animal reproductive body consisting of an ovum together with its nutritive and protective envelopes and having the capacity to develop into a new individual capable of independent existence. ENDANGERED SPECIES Legally, a species or population species that has been placed on a state or federal endangered species list; generally, a species or population that has declined to the point that it is in imminent danger of becoming extinct. ENDOTHERM An organism that warms its body through metabolic processes fueled by the food that it eats. EX TIRPATION The extinction of an animal from a specific portion of its range. FEMORAL PORE A relatively deep pit in the center or near the posterior edge of an enlarged scale or series of scales along the ventral surface of the thighs of some lizards. FORELIMB Front of the furthest tip of the toes (digits) to the elbow. FOSSORIAL Adapted to living underground. FRACTURE PL ANES Divisions in the caudal (tail) vertebrae of most lizards; fracture planes allow the tail to be readily shed when grasped by a predator. GENERALIST A species able to exploit a wide variety of foods or habitats. GRANUL AR SCALE In some lizards, a small, convex, nonoverlapping skin scale that gives the skin surface a pebbled appearance or, when very small and fi ne, a velvety appearance. GRAVID Describing the condition of reptiles and amphibians when carrying eggs internally. GROUND COLOR The main background color of an organism. GUL AR FOLD An external fold or flap of tissue that extends across the lower throat region of lizards. HABITAT An area in the environment capable of supporting all the needs of a particular organism or species. 319

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Glossary

HERPETOCULTURE The maintenance and captive propagation of reptiles, turtles, crocodilians, and amphibians. HYBRIDIZATION A process in which members of 2 species mate successfully and produce offspring; the offspring typically show at least some degree of reduced fertility, ranging from complete sterility (as with mules) to reduced fertility (as with hybrid snakes, which may produce 50 percent viable and 50 percent infertile eggs) to the production of fully fertile offspring, which nonetheless frequently exhibit characteristics that reduce their ability to survive in the environment. IGUANIANS Lizards that for the most part have fleshy, short, nonextendable tongues and primarily locate food by sight. INFRAL ABIAL SCALES A series of scales covering the lower lip. INTEGUMENT Skin. INTERGRADE In reference to biological forms, to blend into one another, presumably because of gene flow between taxa. INTERNASAL SCALE A scale that lies between the nasals on the heads of some lizards. INTERORBITAL SCALE A scale that lies between the orbits on the dorsal surface of the head. INTERPARIETAL SCALE A head scale of a lizard that lies between the parietal scales. JUVENILE A sexually immature individual. KEELED SCALES Scales on some lizards and snakes that have a ridge along the longitudinal midline. L ABIAL Pertaining to the lip. L ATERAL Toward the sides of the body. L ATERAL FOLD A fold of skin that runs from the side of the head to the hind limbs along the lateral surfaces of some lizards having bony, armored skins; it allows expansion of the body for breathing, feeding, and the carrying of eggs by gravid females. LIZARD A squamate organism having some combination of moveable eyelids, external ears, 4 limbs, clawed toes, scales, and a long tail. LOREAL SCALES Rectangular or squarish scales on the side of the head between the nasal and preocular scales of lizards. MEDIAN Midline of the body. MEL ANISTIC Referring to an exceptionally dark individual or structure that owes its coloration to the presence of large quantities of the pigment melanin. MENTAL SCALE A scale at the anterior edge of the lower jaw of lizards. MESIC Referring to a habitat type with a moderate supply of moisture. MICROHABITAT A smaller part of an organism’s overall habitat that has unique characteristics. MONOPHYLETIC A situation in which a named taxon includes all descendants of a single common ancestor. 320

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Glossary

MORPH One of a smaller number of variants in color or morphology that occur in a group. NARIS (PLURAL: NARES) A nostril or external opening to the nasal passages. NASAL SCALE In a lizard, a scale on the side of the head that includes the naris. NEONATE A hatchling or newborn animal. NOCTURNAL Active at night. NOMENCL ATURE A method of naming; in biology, the system of scientific names applied to taxa. NONGAME SPECIES All species of wildlife that are not hunted for sport as game animals. NUCHAL Pertaining to the back of the neck. OVERGRAZING The excessive pasturing of livestock on rangelands, resulting in loss of vegetative ground cover. OVIPAROUS Egg-laying. OVIPOSIT To lay eggs. OVOVIVIPAROUS Giving birth to live young that are enclosed within all the membranes of the amniotic egg except the shell. PARAPHYLETIC A situation in which a named taxon does not include all members of a single common ancestor. PARIETAL SCALES One or more scales that cover the occipital or rear portion of the head of lizards. PARTHENOGENESIS The production of offspring without fertilization of eggs by sperm. PEST SPECIES Any species deemed unwanted by humans. PHYLOGENETIC SYSTEMATICS The field of biology that uses the characteristics of organisms—including morphological, behavioral, or genetic features—to infer the relationships between populations within species of organisms, between different species of organisms, or between groups of organisms described by higher taxonomic categories such as families or orders. PINEAL EYE An outgrowth of the pineal gland present on the top of the head in lizards; it aids in thermoregulation. PL ACENTAL Describing live-bearing organisms (including some lizards and most mammals) in which the amniotic membranes are modified to produce an interface between the embryo and mother inside the uterus. POPUL ATION All members of a species living in the same place at the same time. POPUL ATION DENSITY Numbers of individuals in a population divided by unit area. POSTANTEBRANCHIAL SCALES Scales on the underside of the forelimb, usually toward the elbow. 321

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Glossary

POSTERIOR Pertaining to the back end or rear part of the animal. POSTFEMORAL POCKET A fold or pocket of skin behind the insertion

of the hind limb in some lizards. POSTL ABIAL SCALES A series of large or small scales lying posterior to

and in line with the labial scales. POSTMENTAL SCALES A series of paired or unpaired scales lying along the midventral line immediately posterior to the mental scale on the lower jaw. POSTNASAL SCALE A scale or series of scales lying behind the nasal scale and in front of the loreal scales. POSTOCUL AR SCALES A series of scales at the posterior edge of the orbit. PREFRONTAL SHIELDS A scale or series of scales immediately anterior to the frontal scale. PREOCUL AR SCALES A scale or series of scales at the anterior edge of the orbit. PSEUDOCOPUL ATION A behavior seen in parthenogenetic all-female lizards in which a “male-acting” female assumes a stereotypical copulatory position with an ovulating female to increase her fertility. REGENERATION The regrowth of a lost body part; in the case of lizards, the tail. REPTILES Formerly, a group of vertebrate organisms including turtles, crocodilians, lizards, snakes, amphisbaenians, and the tuatara; as currently understood, this group is restricted to the lizards, snakes, amphisbaenians, and the tuatara. RIPARIAN A zone along a river or stream where water from the stream is available as groundwater to vegetation, typically resulting in more luxurious vegetative growth than in surrounding areas. ROSTRAL SCALE The scale at the tip of the snout. SAL AMANDER A four-legged, tailed amphibian. Salamanders are frequently confused with lizards. SAVANNAH A land area where small trees are interspersed with grasses. SA XICOLOUS Rock-dwelling. SCIENTIFIC NAME The unique combination of names assigned to a particular species. It consists of the genus name and a specific epithet, and is used to identify that species to scientists and in scientific literature. SCLEROGLOSSA A group of animals, including lizards, that have extendable, forked tongues used to detect chemical signals from their environments. Th is group also includes amphisbaenians and snakes. SEMIFOSSORIAL Describing a way of life that primarily involves burrowing under leaf litter and other surface detritus rather than under the soil. 322

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SNAKES Squamate lizard relatives having forked tongues and lacking external limbs and moveable eyelids. SNOUT-VENT LENGTH The distance from the tip of the snout to the posterior margin of the cloaca. SPECIALIST A species adapted to exploit very specific foods or habitats. SQUAMATA The order of reptiles that includes the lizards, snakes, and amphisbaenians. SUPRAL ABIAL SCALES A series of scales that cover the upper lip. SUPRANASAL SCALES A scale or series of scales lying directly above the nasal scale and lateral to the internasal scale. SUPRAORBITAL SCALES A series of scales that lie on the dorsum of the orbit in lizards. SUSTAINABILITY The capacity of a population or system to remain healthy, diverse, and productive over time, especially in the face of use or harvest of some of its members. SYMPATRIC Describing 2 or more species or groups that have overlapping ranges and live in the same geographic region. TA XON (PLURAL: TA X A) The taxonomic name applied to a group of organisms. TA XONOMY The field of biology that categorizes all living things into groups and assigns names to those groups. TEMPORAL SCALES A scale or series of scales lying behind the postoculars, below the parietal, and above the supralabials. TERRITORY An area that is actively defended from competitors—usually members of the same species and sex. THERMOREGUL ATION The process by which an organism controls its body temperature. THORNSCRUB Brushy habitat characterized by thorny trees such as mesquite and acacia. THREATENED SPECIES Legally, a species that has been added to a state or federal threatened species list; generally, a species whose populations have declined to a point at which they are on the brink of becoming endangered. TOTAL LENGTH The distance from the tip of the snout to the tip of the tail. TRIPLOID Having 3 sets of chromosomes instead of the usual 2. TUATARA A primitive, lizard-like reptile that inhabits islands off the coast of New Zealand. TUBERCLE A small to large, rounded or triangular bump on the skin. Typically, an enlarged and raised scale in lizards. ULTRAVIOLET LIGHT Wavelengths of light invisible to humans that are shorter in length and higher in energy than the visible-light spectrum, but longer in length and lower in energy than X-rays. These wave-

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lengths of light are necessary for the synthesis of vitamin D by the skin cells of many animals, including lizards; however, overexposure to ultraviolet light can result in damage to skin cell DNA and to other nutrients (particularly folate, a B-complex vitamin). URBANIZATION The process of altering habitats from natural or agricultural conditions into cities. UREA A water-soluble form of nitrogenous waste. Toxic ammonia is produced by cells as a by-product of the metabolism of proteins in cells. In aquatic organisms such as fish, ammonia may be excreted out of the bloodstream as it is produced, while in terrestrial organisms it is converted into less toxic compounds such as urea, which is then disposed of as urine. URIC ACID An insoluble form of nitrogenous waste found primarily in terrestrial egg-laying organisms that is excreted as a whitish paste. Unlike urea (see above), the excretion of uric acid, although more metabolically expensive, wastes far less water and is commonly used by desert-adapted lizards. VENT In reptiles and amphibians, the common channel into which the digestive, urinary, and reproductive tracts discharge their contents; also referred to as the cloaca. VENTER Belly; the lower surface of an organism. VENTRAL SCALES A series of scales, often enlarged, on the belly of a lizard. VENTROL ATERAL Describing the sides of the belly or the lower surface of the body. VIVIPAROUS Live-bearing. WHORL A symmetrical series of scales around the tail segment of a lizard. XERIC Describes a condition that requires only a small amount of moisture. YOLK OR YOLK SAC Membrane in the amniotic egg that encloses a reservoir of nutrients for the developing embryo.

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BIBLIOGRAPHY Bartlett, R. D., and P. P. Bartlett. 1999. A field guide to Texas reptiles and amphibians. Houston: Gulf. ———. 2006. Guide and reference to the amphibians of eastern and central North America (north of Mexico). Gainesville: Univ. Press of Florida. Cogger, H. G. 1992. Reptiles and amphibians of Australia. 5th ed. Ithaca, N.Y.: Cornell Univ. Press. Conant, R., and J. T. Collins. 1998. A field guide to reptiles and amphibians: Eastern and central North America. Peterson Field Guides. Boston: Houghton Miffl in. Degenhardt, W. G., C. W. Painter, and A. H. Price. 1996. Amphibians and reptiles of New Mexico. Albuquerque: Univ. of New Mexico Press. Dixon, J. R. 2013. Amphibians and reptiles of Texas. 3rd ed. College Station: Texas A&M Univ. Press. Dixon, J. R., and J. A. Lemos-Espinal. 2010. Amphibians and reptiles of the state of Querétaro, Mexico. College Station: Texas A&M Univ. Press; Mexico City: UNAM-CONABIO. Garrett, J. M., and D. G. Barker. 1987. A field guide to reptiles and amphibians of Texas. Austin: Texas Monthly Press. 325

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Bibliography

Gehlbach, F. R. 1981. Mountain islands and desert seas: A natural history of the U.S.-Mexican borderlands. College Station: Texas A&M Univ. Press. Greene, H. W., J. J. S. Rodriguez, and B. J. Powell. 2006. Parental behavior in anguid Lizards. South American Journal of Herpetology 1:9–19. Jones, L. L. C., and R. E. Lovich, eds. 2009. Lizards of the American Southwest: A photographic field guide. Tucson: Rio Nuevo. Lemos-Espinal, J. A., and H. M. Smith. 2007. Amphibians and reptiles of the state of Coahuila, Mexico. Mexico City: UNAM-CONABIO. ———. 2007. Amphibians and reptiles of the state of Chihuahua, Mexico. Mexico City: UNAM-CONABIO. ———. 2009. Keys to the amphibians and reptiles of Sonora, Chihuahua and Coahuila, Mexico. Mexico City: UNAM-CONABIO. Pianka, E. R., and L. J. Vitt. 2003. Lizards: Windows to the evolution of diversity. Berkeley and Los Angeles: Univ. of California Press.

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INDEX OF COMMON NAMES Bold page numbers indicate a detailed discussion. Alligator Lizard Madrean, 22 Texas xi, 16, 20, 57, 60, 76, 293–298, 302 Anole Brown, 42, 43, 76, 184, 187–189 Green, 4, 13, 15, 23, 42, 43, 44, 76, 183–186, 188, 189

Earless Lizard Greater xi, 18, 38, 77, 104–107, 109, 114, 117, 130 Keeled, 77, 109, 116–119 Lesser, 38, 67, 77, 109, 112– 115 Spot-tailed, 23, 38, 77, 108–111, 117

Canyon Lizard, 12, 78, 138, 146–150 Collared Lizard Eastern, 20, 23, 57, 58, 60, 77, 87–90, 91, 93, 96, 97, 180 Reticulated, 78, 86, 88, 91–94

Fence Lizard Eastern, 42, 65, 66, 79, 143, 148, 153, 156, 158–164 Southwestern, 66, 163

Dragon Inland Bearded, 4, 58, 306–307 Komodo, 5

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Gecko Common House, 74, 204, 205–207, 208, 212, 213 Indo-Pacific, 9, 74, 204, 206, 208–210, 212, 213

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Gecko (continued) Mediterranean, 17, 23, 39, 74, 194, 204, 206, 208, 211–213 Reticulated, 5, 68, 76, 194, 197– 201 Rough-tailed, 74, 203–204, 206, 209, 212, 213 Texas Banded, 5, 60, 76, 193– 196, 199, 204, 213 Tokay, 307–308 Tropical House, 209, 213 Gila Monster, 303–304 Glass Lizard, Slender, 22, 35, 39, 60, 73, 299–302 Horned Lizard Greater Short- 77, 121, 125–128, 130, 131 Round-tailed, 19, 77, 121, 126, 129–132 Texas xi, 4, 20, 21, 23, 40, 44, 62, 120–124, 126, 128, 130, 131 Iguana Green, 4, 58, 101, 305–306 Mexican Spiny-tailed, 23, 74, 85, 100–102 Leopard Lizard, Long-nosed, 11, 14, 18, 58, 72, 73, 78, 88, 93, 95–98 Mesquite Lizard, 68, 79, 143, 151– 154, 167 Prairie Lizard, 66, 163 Racerunner, Six-lined, 70, 80, 250, 259, 265–268, 288, 290 Rose-bellied Lizard, 10, 14, 78, 141–145, 148, 153, 154, 167

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Sagebrush Lizard, Dunes, 79, 155–157, 160 Salamander, Dwarf, 2

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Side-blotched Lizard Common, 78, 114, 133–136, 138 Eastern, 136 Skink Broad-headed, 14, 16, 72, 75, 76, 215, 228, 229, 231–234 Coal, 75, 216–219, 221, 224, 229 Five-lined, 68, 72, 75, 76, 217, 227–230, 232, 234 Florida Sand, 215 Four-lined, 75, 217, 221, 223– 226 Great Plains, 49, 57, 58, 60, 72, 73, 74, 218, 224, 231, 235, 239–243, 295 Ground, 2, 5, 49, 68, 74, 217, 221, 224, 236, 244–246 Many-lined, 38, 75, 224, 235– 238, 241 Prairie, 35, 75, 217, 220–222, 224, 229 Spiny Lizard Blue, 79, 91, 167, 174–177, 179, 180 Crevice, 8, 78, 88, 167, 171, 176, 177, 178–181 Desert, 66, 72, 78, 89, 97, 167, 170–173, 180 Texas, 5, 8, 17, 23, 35, 79, 121, 143, 153, 160, 165–169, 171, 176, 179 Twin-spotted, 66, 173 Tegu Black, 247 Red, 247 Tree Lizard, Ornate, 28, 134, 137–140, 148, 153 Whipsnake, Striped, 3 Whiptail Canyon Spotted, 279, 286, 287 Chihuahuan Spotted, 68, 80, 251, 253, 255, 260, 276–279, 281, 284, 287 Colorado Checkered, 275

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Common Checkered, 67, 81, 251, 257, 262, 264, 270, 272–275 Desert Grassland, 80, 259, 260, 279, 281, 284–287 Gray Checkered, 67, 81, 257, 262, 264, 269–271, 272, 275 Laredo Striped, 70, 80, 251, 253, 268, 288–290 Little Striped, 80, 247, 251, 255, 258–260, 266, 279, 281, 283, 284, 286, 287, 288 Marbled, 18, 19, 38, 49, 81, 96, 251, 255, 261–264, 270, 271, 272, 275, 283

Mexican Plateau, 66, 67, 257 New Mexico, 72, 81, 260, 264, 274, 276, 280–283 Rusty-rumped, 3, 66, 67, 81, 251, 254–257, 62, 270, 271, 272, 275 Sonoran Spotted, 68, 69 Texas Spotted, 5, 66, 67, 68, 70, 80, 143, 249–253, 255, 256, 257, 266, 276, 279, 288, 290 Western, 264 Worm Lizard, Florida, 3 Zebra-tailed Lizard, 18

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INDEX OF SCIENTIFIC NAMES Bold page numbers indicate a detailed discussion. Anolis carolinensis, 4, 13, 15, 23, 42, 43, 76, 183–186, 188 sagrei, 42, 43, 76, 184, 187–188 Aspidoscelis burti, 279, 286 dixoni, 67, 81, 255, 257, 262, 264, 269–271, 272, 275 exsanguis, 80, 251, 253, 255, 260, 276–279, 281, 284, 287 gularis, 5, 66, 68, 70, 80, 143, 249–253, 255, 256, 257, 266, 276, 279, 288, 290 inornata, 80, 247, 251, 255, 258– 260, 266, 279, 281, 283, 284, 286, 288 laredoensis, 70, 80, 251, 253, 268, 288–290

marmorata, 18, 19, 38, 49, 81, 96, 251, 255, 261–264, 270, 271, 272, 275, 283 neomexicana, 72, 81, 260, 264, 274, 276, 280–283 neotesselata, 275 scalaris, 66, 257 septemvittata, 3, 66, 81, 251, 254–257, 262, 270, 271, 273, 275 sexlineata, 70, 80, 250, 259, 265–268, 288, 290 tesselata, 67, 81, 251, 255, 257, 262, 264, 270, 272– 275 tigris, 264 uniparens, 80, 259, 260, 279, 281, 284–287 3 31

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Callisaurus draconoides, 18 Coleonyx brevis, 5, 60, 76, 193–196, 198, 204, 213 reticulatus, 5, 68, 76, 194, 197– 201 Cophosaurus texanus, 18, 38, 77, 104–107 Crotaphytus collaris, 20, 23, 57, 58, 77, 87– 90, 93, 96, 180 reticulatus, 78, 91–94 Ctenosaura pectinata, 23, 74, 100– 102 Cyrtopodion scabrum, 74, 203– 204, 206, 209, 212, 213 Elgaria kingii, 22 Eurycea quadridigitata, 2 Gambelia wislizenii, 11, 14, 18, 58, 72, 73, 78, 93, 95–98 Gekko gekko, 307–308 Gerrhonotus infernalis, 16, 20, 57, 76, 293– 298, 302 liocephalus, 298 taylori, 298 Heloderma suspectum, 303–304 Hemidactylus frenatus, 74, 204, 205–207, 206, 208, 212, 213 garnoti, 9, 74, 204, 206, 208– 210, 212, 213 mabouia, 209, 213 turcicus, 17, 23, 39, 74, 194, 204, 206, 208, 211–213, 308 Holbrookia lacerata, 23, 38, 77, 108–111 maculata, 38, 67, 68, 77, 109, 112–115 propinqua, 77, 109, 116–119

Iguana iguana, 4, 58, 101, 305–306 Masticophis taeniatus, 3 Ophisaurus attenutus, 22, 35, 39, 73, 299–302 Phrynosoma cornutum, 4, 20, 21, 23, 40, 44, 62, 63, 77, 120–124 hernandesi, 77, 121, 125–128 modestum, 19, 77, 121, 129–132 Plestiodon anthracinus, 75, 216–219, 221, 224, 229 fasciatus, 63, 68, 72, 76, 217, 227–230, 232 laticeps, 14, 16, 72, 75, 76, 215, 228, 229, 231–234 multivirgatus, 38, 75, 224, 235– 238, 241 obsoletus, 49, 57, 72, 73, 74, 218, 224, 231, 236, 239–243, 295 reynoldsi, 215 septentrionalis, 35, 75, 217, 220– 222, 224, 229 tetragrammus, 75, 217, 227–230, 232 Pogona vitticeps, 4, 58, 306–307 Rhineura floridana, 3 Sceloporus arenicolus, 79, 155–157, 160 bimaculosus, 66, 173 consobrinus, 66, 163 cowlesi, 66, 163 cyanogenys, 63, 79, 91, 167, 174– 177, 179 grammicus, 68, 79, 143, 151–154, 167 magister, 66, 72, 78, 89, 97, 167, 170–173, 180

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merriami, 12, 78, 138, 146–150 olivaceus, 5, 8, 17, 23, 35, 79, 121, 143, 153, 160, 165–169, 171, 176, 179 poinsetti, 8, 78, 88, 167, 171, 176, 177, 178–181 serrifer, 177 undulatus complex, 42, 65, 66, 79, 143, 148, 153, 156, 158–164, 163, 164, 167 variabilis, 10, 14, 78, 141–145, 148, 153, 167

Scincella lateralis, 2, 5, 49, 68, 74, 217, 221, 224, 236, 244–246 Urosaurus ornatus, 78, 134, 137– 140, 148, 153 Uta stansburiana, 78, 114, 133–136, 138 stejnegeri, 136 Varanus komodoensis, 5

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