Amphibians of Western North America [2nd printing, Reprint 2020 ed.] 9780520331563

Citation preview

R O B E R T G. STEBBINS

of western Berkeley and Los Angeles

1962

UNIVERSITY OF C A L I F O R N I A PRESS

Iflortk Mmenca

UNIVERSITY O F C A L I F O R N I A PRESS, B E R K E L E Y AND LOS ANGELES, CAMBRIDGE U N I V E R S I T Y COPYRIGHT,

1951,

SECOND PRINTING, MANUFACTURED

PRESS, LONDON,

B Y T H E REGENTS O F T H E U N I V E R S I T Y 1962

IN T H E

CALIFORNIA

ENGLAND

UNITED STATES O F

AMERICA

OF

CALIFORNIA

To Cyril and Louise

Stebbins

PREFACE

T h i s book provides information on the external form and coloration, habits, and distribution of the species of amphibians inhabiting western North America. It includes a comprehensive coverage of the pertinent literature, unpublished data in field notebooks in the University of California Museum of Vertebrate Zoology, and the author's personal observations. T h e bibliography consists only of literature cited and hence represents but a portion of the total writings relating to western amphibians. Distributional lists, for example, although used in the preparation of the maps, have often been omitted. Several summarizations of literature are available (Bishop, 1943, for the salamanders and Wright and Wright, 1949, for the anurans), hence I have not thought it essential to present a complete bibliography. T h e book includes all the known species of amphibians in an area delimited as follows: North America north of the Mexican border and west of a line formed by the eastern boundaries of New Mexico, Colorado, Wyoming, Montana, projected northward along the eastern border ot Saskatchewan, Canada (see map, page 2). All species, and some subspecies, where differences are marked, have been illustrated. T o facilitate identification and comparisons, the animals of each major group (salamanders and anurans) are similarly posed. Similarities and differences in size, form, and pigmentation hence may be quickly noted. Tentative identification of species may be made by refervii

viii —

Amphibians

ence to the illustrations. Keys are provided for more precise determinations. With few exceptions, salamanders are shown in dorsal and ventral views, frogs and toads in three-quarter view. T h e drawings are based on representative animals, but some have been modified to emphasize diagnostic features or when in some respect the subject was atypical. I have put into the volume what I have wanted to know about our western amphibians and hope in so doing to have anticipated questions of persons using the book. Much remains to be learned, as is readily seen from even a casual inspection of the following pages. Some suggestions of problems and questions may be found at the end of the accounts of genera and species. Many persons have aided in the preparation of the book and to them I wish to extend my sincere appreciation. Dr. Jean M. Linsdale of the Hastings Natural History Reservation of the University of California read most of the accounts of species. Those who have read parts or all of the manuscript at one stage or another in its development are: Charles M. Bogert of the American Museum of Natural History; Dr. Raymond Cowles, Professor of Zoology at the University of California, Los Angeles; Dr. Richard Eakin, Professor of Zoology at the University of California, Berkeley; Dr. Laurence Klauber of the San Diego Museum of Natural History; Dr. Charles H. Lowe, Jr., University of Arizona; Dr. Alden H. Miller, Director of the Museum of Vertebrate Zoology; C. B. Perkins, in charge of amphibians and reptiles at the San Diego Zoo; and William Riemer, assistant in herpetology at the Museum of Vertebrate Zoology. Dr. Victor Twitty of Stanford University has given me information on newts. On a number of occasions I have had the advice and counsel of Dr. Seth Benson, Curator of Mammals at the Museum of Vertebrate Zoology. Dr. Robert Usinger, Associate Professor of Entomology at the University of California, checked accuracy of nomenclature in the lists of insects fed upon by amphibians. John Hendrickson of the University of California, and Dr. Robert Storm of Oregon State College have provided information on several species. T h e following individuals and institutions have loaned specimens for study and illustration: Mr. Bogert; Dr. Arthur Bragg, University of Oklahoma; Dr. Walter Breckenridge, Curator, Minnesota Museum of Natural History; Dr. Doris Cochran, United States National Museum; Dr. Ian McTaggart Cowan, University of British Columbia; Dr. George Myers, Stanford University Museum of Natural History; Dr. James Slater, College of Puget Sound, Washington; and Joseph Slevin, Herpetologist, California Academy of Sciences. My brother, Ernest Stebbins, and Mr. Riemer assisted me with field work. T h e following persons have given me information and advice in the preparation of the distribution maps: Mr. Bogert (southwestern United States and Mexico), Dr. Cowan (Canada), Dr. Ira LaRivers and Benjamin Banta (Nevada), Dr. Lowe, Jr. (Arizona and New Mexico), Dr. T . Paul

O F WESTERN N O R T H A M E R I C A

ix

Maslin (Colorado), Kenneth Norris (New Mexico), Dr. Slater (Washington), Dr. Storm (Oregon), Dr. Angus Woodbury (Utah), and Richard Zweifel (southern California, New Mexico, and Sonora, Mexico). Dr. Breckenridge, Dr. Robert Livezey, University of Notre Dame, and Mr. Clifford Pope, Chicago Natural History Museum, have permitted me to draw upon materials published by them. T o these and many others to whose writings I have referred, I recognize my indebtedness. Dr. Albert Wright, Professor of Zoology (emeritus), Cornell University, and his wife, Anna Wright; Dr. Sherman Bishop, University of Rochester; Dr. Emmett R. Dunn, Haverford College; and Dr. Tracy I. Storer, Professor of Zoology, University of California, Davis, are outstanding among those whose published works have been a constant source of inspiration and assistance. Doubleday, Page and Company and the Comstock Publishing Company permitted me to quote, respectively, from Mary Dickerson's The Frog Book and Albert and Anna Wright's Handbook of Frogs and Toads. Miss Marian John and Miss Adele Zimmerman typed most of the manuscript and Mrs. Lois Taylor aided with the lettering of plates. Miss Susan Chattin and my wife helped in many ways in bringing the book to final form. Dr. Storer generously permitted extensive use of notes that he had accumulated in contemplation of a revision of his Amphibia of California. Information abstracted from these notes appears in the text as Storer (MS). This volume to a considerable extent has been fostered by a John Simon Guggenheim Memorial Fellowship, whose financial support has greatly facilitated its preparation. Illustrations were prepared by me, unless otherwise credited. R. C. S. University of California, Berkeley, July, 195!.

Introduction Class AMPHIBIA—Characterization

Salamanders Order Urodela—Characterization Accounts of Species

CONTENTS

14 - NEWTS Family Salamandridae Genus Triturus 17 R O U G H SKIN N E W T Triturus granulosus (Skilton) 21 W E S T E R N RED-BELLIED N E W T Triturus rivularis Twitty 23 C A L I F O R N I A N E W T Triturus torosus (Rathke) 29 - AMBYSTOMIDS Family Ambystomidae 31 Genus Ambystoma 32 N O R T H W E S T E R N S A L A M A N D E R Ambystoma gracile (Baird)

Salamanders

36 -

L O N G - T O E D S A L A M A N D E R Ambystoma macrodactylum Baird

40 -

T I G E R S A L A M A N D E R Ambystoma tigrinum Genus

49 -

55 -

(Green)

Dicamptodon

PACIFIC G I A N T S A L A M A N D E R Dicamptodon (Eschscholtz) Genus Rhyacotriton O L Y M P I C S A L A M A N D E R Rhyacotriton (Gaige)

ensatus

olympiens

61 - LUNGLESS S A L A M A N D E R S Family Plethodontidae 63 -

Genus Plethodon

68 -

D U N N S A L A M A N D E R Plethodon dunni Bishop

72 -

DEL N O R T E S A L A M A N D E R Plethodon Denburgh

76 -

JEMEZ M O U N T A I N S S A L A M A N D E R Plethodon mexicanus Stebbins and Riemer

80 -

V A N DYKE Denburgh

84 -

87 -

WESTERN vehiculum Genus Ensatina

SALAMANDER RED-BACKED (Cooper)

Plethodon

neo-

vandykei Van

SALAMANDER

Plethodon

S A L A M A N D E R Ensatina

eschscholtzii

108 -

C A L I F O R N I A SLENDER S A L A M A N D E R attenuatus (Eschscholtz)

Batrachoseps

115 -

PACIFIC SLENDER S A L A M A N D E R Batrachoseps pacificus (Cope)

120 -

O R E G O N SLENDER S A L A M A N D E R wrighti (Bishop)

105 -

125 -

ESCHSCHOLTZ Gray

elongatus Van

Genus Batrachoseps

Batrachoseps

Genus Aneides

126 -

C L O U D E D S A L A M A N D E R Aneides ferreus Cope

131 -

B L A C K S A L A M A N D E R Aneides

135 -

SACRAMENTO MOUNTAINS SALAMANDER hardii (Taylor)

139 -

A R B O R E A L S A L A M A N D E R Aneides lugubris (Hallowell)

flavipunctatns

(Strauch) Aneides

Genus Hydromantes 146 -

M O U N T L Y E L L S A L A M A N D E R Hydromantes alus (Camp)

platyceph-

frogs and Toads Order Anura—Characterization - 181 Accounts of Species

187 - B E L L T O A D S Family Ascaphidae (Liopelmidae) Genus Ascaphus 188 A M E R I C A N B E L L T O A D Ascaphus truei Stejneger 194 - S P A D E F O O T T O A D S Family Pelobatidae Genus Scaphiopus 197 C O U C H S P A D E F O O T Scaphiopus couchii Baird 202 C E N T R A L P L A I N S S P A D E F O O T Scaphiopus bombifrons Cope 207 H A M M O N D S P A D E F O O T Scaphiopus hammondii Baird 218 - L E P T O D A C T Y L I D S Family Leptodactylidae Genus Eleutherodactylus 219 B A R K I N G F R O G Eleutherodactylus latrans (Cope) 225 - T O A D S Family Bufonidae 226 Genus Bufo 229 C O L O R A D O R I V E R T O A D Bufo alvarius Girard 234 W E S T E R N T O A D Bufo boreas Baird and Girard 245 Y O S E M I T E T O A D Bufo canorus C a m p 249 G R E A T P L A I N S T O A D Bufo cognatus Say 255 S O N O R A N T O A D Bufo compactilis W i e g m a n n 259 L I T T L E G R E E N T O A D Bufo debilis Girard 263 C A N A D I A N T O A D Bufo hemiophrys Cope 266 C O P E T O A D Bufo microscaphus Cope 280 D E S E R T T O A D Bufo punctatus Baird and Girard 286 W O O D H O U S E T O A D Bufo woodhousii Girard 294 - T R E E - T O A D S Family Hylidae Genus Acris 296 C R I C K E T - F R O G Acris gryllus (Le Conte) Genus Pseudacris 305 S W A M P C R I C K E T - F R O G Pseudacris nigrita (Le Conte) Genus Hyla 313 C A N Y O N T R E E - T O A D Hyla arenicolor Cope 322 P A C I F I C T R E E - T O A D Hyla regilla Baird and Girard 327 S O N O R A N T R E E - T O A D Hyla wrightorum T a y l o r 330 - T R U E F R O G S Family Ranidae Genus Rana 334 R E D - L E G G E D F R O G Rana aurora Baird and Girard 339 Y E L L O W - L E G G E D F R O G Rana boylii Baird 345 B U L L F R O G Rana catesbeiana Shaw 351 G R E E N F R O G Rana clamitans Latreille

frogs and Toads

Eggs and Larvae Habitats

355 367 373 382 387

LEOPARD F R O G Rana pipiens Schreber S P O T T E D F R O G Rana pretiosa Baird and Girard ~ W O O D F R O G Rana sylvatica Le Conte MEXICAN F R O G Rana tarahumarae Boulenger - MICROHYLIDS Family Microhylidae Genus Microhyla 388 N A R R O W M O U T H T O A D Microhyla carolinensis (Holbrook)

419 - EGGS 435 - LARVAE

489 509 513 515 531

-

D I S T R I B U T I O N MAPS GLOSSARY E X P L A N A T I O N OF ABBREVIATIONS BIBLIOGRAPHY INDEX

INTRODUCTION

Among the major groups of vertebrates, amphibians constitute a small and generally inconspicuous class, although some species are abundant as individuals. T h e small size of many, their secretive habits, and in some areas their short periods of activity, often render them difficult to observe. With knowledge of the time of activity and manner of occurrence of species, however, one can be relatively sure of finding them. Many are sedentary, moving but short distances in a lifetime, and most are sharply limited in their tolerance of extremes in environmental factors such as humidity and temperature. They commonly require water for breeding and all must live in an environment that provides sufficient moisture to prevent excessive dehydration. Some resemble plants in their sedentary nature and dependence on soil moisture. Under terrestrial conditions, one might designate a "wilting point" (Lowe, 1950:96) for these animals, reached when the absorption of water, obtained through the skin and from food, fails to keep pace with evaporation from the surfaces of the body. Standing as they do between the aquatic and terrestrial modes of existence among vertebrates, amphibians present a profitable field for investigations bearing on the evolution of land life. Further, the occurrence of many species in small, weakly connected, or separate populations in suit-

Amphibians

OF WESTERN NORTH AMERICA

—

3

able areas in otherwise generally unfavorable habitats, provides a favorable situation for the study of environmental effects on the structure and dynamics of populations. There are a number of publications that provide information of a general sort on the natural history of amphibians (Noble, 1931; Holmes, 1927; introductory sections of Bishop, 1943; Dickerson, 1920; Wright and Wright, 1949, and others). I have confined myself principally to assembling facts on species. Such information is gathered under species accounts that form the bulk of the book. Some explanatory remarks regarding these accounts are required. I have selected, on the basis of popularity and appropriateness, a single common name for each species. I favor the trend that prevails among ornithologists toward standardization of common names. It is, however, probably too early in the development of herpetological nomenclature to press for such standardization. The type locality is given for each species, principally for its historical interest. The author of the species is indicated following the type locality. The locality is not always stated as in the original description since sometimes a clearer or more precise localization can be made. In a few species, rare or difficult to find, other localities have been listed. Descriptions of species give estimates of range in size of adults and are not to be considered as precise determinations. Measurements are of total length for salamanders, snout-vent length for anurans, unless otherwise indicated. Emphasis has been placed on colors in life and descriptions are to be so viewed unless otherwise stated. Ridgway (1912) references have seldom been employed since much of the color terminology is meaningless in the absence of the Ridgway charts. When used, however, they are capitalized to distinguish them from less precise color references. Colors generally are given in conventional terms which, although less objective, are, I believe, more useful to the average reader. Usually following the general account of pigmentation are descriptions, in small type, of one or more specific individuals from selected localities. Such descriptions are considered desirable in view of the scant information on life colors of amphibians. Colors change markedly with preservation. Under the section "Habitat," often a summarization of information on occurrence of the species is given. This summary is commonly followed by one or more descriptions of specific situations under which animals were found. These samples are largely selected from personal field notes and are presented with the thought that such detail may aid in finding animals and in gaining an impression of their habitat requirements. Under the section "Reproduction" in the accounts of species, "Season" refers to the span of breeding activity. In some species this may represent

4 —

Amphibians

OF W E S T E R N

NORTH

AMERICA

essentially the total period of surface activity but in others, nonbreeding individuals may be found before and after this period. The keys have been fully illustrated because of the subtle nature of many of the characters. The longer keys have references facilitating working backward, a procedure sometimes desired. Thus, if one is at category 7b.(2a), (2a) refers to the category that directed the reader to 7b. Descriptions of subspecies are arranged in key form, although for some the characters are rather vague and of dubious diagnostic value. Characters, such as proportional differences, although ordinarily not very useful as key characters, do, at least, indicate trends of variation, knowledge of which may be of value.

CLASS AMPHIBIA

Characterization.—Vertebrates with moist glandular skin, devoid of dermal appendages such as scales, feathers, and hair that characterize, respectively, the fishes and reptiles, birds, and mammals; limbs commonly 4, but sirenids with only anterior pair, and limbs absent in caecilians; toes commonly 4 on forefoot and 5 on hind foot, sometimes 4-4 or fewer (3-3 or 2-2), typically without claws, although some species with horny tips on digits; tail present (salamanders and caecilians) or absent (frogs and toads); when present, rounded or compressed (aquatic species); feyes commonly with movable lids, upper one usually depressed by retraction of eyeball; lower lid in anurans typically with thin transparent portion (nictitating membrane) retractable behind inert lower lid; salamanders without nictitating membrane; some amphibians with nonmovable transparent covering over eyes (larvae, pipid toads, and some aquatic salamanders); nostrils paired, often valvular; external ears (ear drum) absent (salamanders) or present (many anurans); mouth with fine, somewhat conical teeth in both upper and lower jaws (salamanders, some anurans), teeth absent in lower jaw (ranids and others) or wholly lacking (toads); vomerine teeth in salamanders and most anurans and parasphenoid teeth in some salamanders (plethodontids); tongue commonly present (absent in pipid toads) and protrusible (Ascaphus and others excepted), in some, 5

6 —

Amphibians

OF WESTERN NORTH A M E R I C A

extensively so (to about y s length of body in some salamanders); heart 2- or 3-chambered, single ventricle; 1 to 3 pairs of aortic arches; red blood cells typically oval and nucleated (largely without nuclei in Batrachoseps). Respiration by gills, lungs, buccopharynx, skin, separately or in combination; lungs may be reduced in stream-dwelling types and are absent in plethodontid salamanders; gills typically present at some stage of life history; voice generally absent in salamanders (Dicamptodon and a few others excepted) but many anurans have vocal cords and resonating pouch (or pouches) in throat region; voice best developed in male anurans; ectothermic (poikilothermic), deriving body temperature from surroundings (air, water, substratum, etc.). Fertilization external (majority of anurans and some salamanders) or internal (many salamanders); most species oviparous; eggs with varying amounts of yolk (particularly abundant in plethodontid salamanders and some anurans); ova pigmented or not, covered with one or more gelatinous envelopes, commonly deposited in water but sometimes in damp places on land; cleavage commonly holoblastic but meroblastic in some plethodontid salamanders; most with an aquatic larval stage with transformation to adult form.

Salamanders

SALAMANDERS

Order Urodela Characterization.—Body elongate, with distinct head, trunk, and tail; costal grooves present or not; tail round or compressed, sometimes with well-developed fins; limbs typically 4 (only anterior pair present in sirenids), about equal in size; toes 2-2 to 4-5; eyes w i t h or without movable lids; no nictitating membrane; no external ear; teeth in both jaws; vomerine and sometimes parasphenoid teeth present; tongue commonly protrusible, broadly attached, attached medially and in front, or free all around (pedicelled); voiceless (few exceptions); larva terrestrial or aquatic; aquatic larva with teeth in both jaws, eyes without movable lids, tail compressed and finned; forelimbs and hind limbs grow more or less together, balancer present or absent; aquatic larva generally classified as either pond or brook type; fertilization internal except in Hynobiidae, Cryptobranchidae, and probably Sirenidae; about 150 species (Storer 1943:605)-

9

upper eyelid gulor region gulor fold pectoral region-'' >

axilla

i !

belly or venter-----' ^ axilla to groin costal fold N

costal groove groin or inguen''

y'

pelvic region vent

«»''

Fig. i. External characteristics of a salamander (Aneides

10

fiavipunctatus).

n®

dark nuptial excrescences

m'^M

Trituras

granulosus (