Secrets of Snakes: The Science beyond the Myths (Volume 61) (W. L. Moody Jr. Natural History Series) [1 ed.] 1623497973, 9781623497972

Citation preview

Secrets of Snakes

NU MBER S IX TY- ONE

W. L. Moody Jr. Natural History Series

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Secrets of

SNAKES

THE SCIENCE BEYOND THE MYTHS

David A. Steen

T E X A S A & M U N I V E R S I T Y P R E S S   C O L L E G E S TAT I O N

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Copyright © 2019 by David A. Steen All rights reserved First edition This paper meets the requirements of ANSI/NISO Z39.48–1992 (Permanence of Paper). Binding materials have been chosen for durability. Manufactured in China by Everbest Printing Co. through FCI Print Group

L I B R A RY O F C O N G R E S S C ATA LO G I N G - I N - PU B L I C AT I O N DATA Names: Steen, David A., 1979– author. Title: Secrets of snakes : the science beyond the myths / David A. Steen. Other titles: W.L. Moody Jr. natural history series ; no. 61. Description: First edition. | College Station : Texas A&M University Press, [2020] | Series: W.L. Moody Jr. natural history series ; number sixty-one Identifiers: LCCN 2019002940| ISBN 9781623497972 (book/flexbound : alk. paper) | ISBN 9781623497989 (e-book) Subjects: LCSH: Snakes—United States. | Snakes—United States—Identification. | Snakes—United States—Miscellanea. Classification: LCC QL652 .S84 2020 | DDC 597.96—dc23 LC record available at https://lccn.loc.gov/2019002940

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D E D I C AT I O N

There are tons of danger noodles, nope ropes, and long bois throughout our streams, our forests, and our backyards; they silently live alongside us every day but could not care less about what we think. This book is dedicated to all the people wanting to learn more about them anyway.

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contents

Foreword, by Harry W. Greene  ix Preface xi Acknowledgments xix

Part I. Identifying Snakes 1 C HAPTER 1.

The Shape of a Snake’s Head Does Not Reveal the Danger 3 C HAPTER 2. Are Snakes with Red on Black Truly a Friend of Jack? 9 C HAPTER 3. What Is the Difference between a Cottonmouth and a Water Moccasin? 13 C HAPTER 4. How Can You Tell a Copperhead from a Cottonmouth? 16 HAPTER 5. Is This a Black Snake? 21 C Species Profile: The Ratsnakes  25 CHAPTER 6. CHAPTER 7. CHAPTER 8.

Can You Tell Whether a Snake Is Venomous by the Way It Swims? 28 It Is Shaking Its Tail; Is It a Rattlesnake? 32 Can You Tell If a Snake Is Venomous by the Shape of Its Pupils? 35

Part II. Snake Myths and Misconceptions 39 HAPTER 9. Are Baby Snakes More Dangerous Than Adults? 41 C HAPTER 10. Do Snakes Travel in Pairs? 46 C HAPTER 11. Is It a Bad Year for Snakes? 52 C CHAPTER 12. Can You Fall into a Nest of Cottonmouths? 59 HAPTER 13. Should You Worry about Stepping into a C Cottonmouth Breeding Ball? 63

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Species Profile: Gophersnake, Pituophis catenifer 66 CHAPTER 14. Will a Cottonmouth Drop into My Boat? 68 CHAPTER 15. CHAPTER 16. CHAPTER 17. CHAPTER 18. CHAPTER 19.

Can a Rattlesnake’s Rattle Tell You How Old the Snake Is? 73 Cottonmouths North of Virginia? I Don’t Think So 76 Are Snakes Aggressive? 80 Are Rattlesnakes Rattling Less Because of Hogs? 86 Will Cottonmouths Chase and Bite You? 90

Part III. Understanding Snakes 95 CHAPTER 20. How Big Do Rattlesnakes Get? 96 CHAPTER 21. Can Snakes Bite Underwater? 101 CHAPTER 22. Is Relocating a Snake from My Yard a Death Sentence? 106 CHAPTER 23. Why It Doesn’t Make Sense to Kill Snakes in Your Yard 112

Species Profile: Dekay’s Brownsnake, Storeria dekayi 117 HAPTER 24. C HAPTER 25. C HAPTER 26. C HAPTER 27. C HAPTER 28. C HAPTER 29. C

What’s the Most Dangerous Snake? 121 Is This Snake Poisonous? 124 Will It Bite? 128 What Is a Mating Dance? 131 Are Snakes Territorial? 136 How Can I Keep Snakes Out of My Yard? 144

Closing Remarks  149 Notes 151 Selected Bibliography  153 Further Reading   157 Index 159

viii :  CONTENTS

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foreword

Half a century ago the Senegalese conservationist Baba Dioum proclaimed that “in the end, we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught.” Having devoted much of my own career as a scientist and teacher to studying, writing, and lecturing about reptiles, I’ve long believed in the general truth of Dioum’s assertion—sure, there are diverse ways to learn about and love organisms besides sitting in a lecture hall or reading a textbook, but lots of evidence confirms that facts can facilitate caring. For those of us who love snakes and other widely unpopular, sometimes dangerous organisms, effectively providing those facts is a core challenge to changing public attitudes. David Steen has written this wonderful book in hopes of enhancing understanding and thereby appreciation for snakes. Indeed, I believe Secrets of Snakes: The Science beyond the Myths has no peer in the literature for three reasons. First, there’s verisimilitude, so important here because often the task at hand involves convincing our fellow humans that what they thought they knew to be true is utterly false—and some folks get very angry, very fast when told, for example, that cottonmouths won’t chase them and there are no ten-foot-long rattlesnakes! David’s writing exudes credibility because he’s an accomplished field biologist, with numerous detailed, sophisticated studies published in top international journals to his credit, yet he never condescends in making a case based upon the results of scientific inquiry. Second, a crucial principle of good teaching is to know your audience, where they’re starting in terms of knowledge and biases, then meet them there before moving on with the lesson. David’s choice of topics reflects unparalleled experience answering questions, literally many thousands of questions, about wildlife. Thanks to those years of experience with teaching through social media, no space is wasted in this book on forgotten mythical animals like the hoop snake I learned about as a child from my East Texas grandfather; better to expand on other equally baseless old tales that are ever more prevalent today, such as the claim that rattlers are selected by recent environmental changes for not sounding off when threatened.

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The third reason for this book’s effectiveness is that David is a wonderful wordsmith, with an authoritative yet empathetic, conversational, candid, and heartfelt voice; this is a man who clearly cares about people as well as snakes, admits to uncertainties when they exist, and, most importantly, wants you to know the facts and hopes that they will make a difference for nature. If you don’t know much about snakes yet and want to learn, this is the best place imaginable to start—even if what you mainly want is to avoid my favorite organisms, although I hope that by reading David Steen’s very special book you’ll come away more predisposed to like them too. For those who already know quite a lot about snakes and want to encourage others to support our coexistence with these limbless reptiles, urge your local libraries to get Secrets of Snakes: The Science beyond the Myths. Better yet, buy a dozen copies yourself and start handing them out! —Harry W. Greene

x : FOREWORD

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pre face

Snakes! Do any other animals provoke such an extreme reaction? Love them or hate them, nearly everyone is fascinated by them. But despite these creatures being common, widespread, and frequently encountered, they may be more misunderstood than any other group of species. From giant rattlesnakes to mating dances, there are dozens of myths and misconceptions floating around about the snakes alongside us. When I was working on my undergraduate degree at the University of New Hampshire, I met with my advisor, Dr. James Taylor, to discuss developing a research project. I told him that I was interested in studying either muskrats or watersnakes, and he replied that either way I was going to be bitten a lot, but it would be a lot worse to be bitten by a muskrat. And that’s basically how I got my start in herpetology. While I was in school I studied to become a wildlife researcher, and that has been the continued focus of my career; to date I have published dozens of scientific articles and book chapters on the ecology and conservation biology of wildlife in North America. Most of my work has focused on snakes and turtles: I have helped document the impacts of road mortality and recreational fishing on freshwater turtle populations, I have studied how habitats and interactions among species determine why you can find certain snakes in some landscapes and not others, and I have described how you can restore mismanaged forests and their wildlife populations by bringing back natural disturbances such as fire. I am proud of these scientific contributions, but I am probably known in my field primarily for something else entirely, something I never even trained for: communicating science to people who would not consider themselves scientists. My science communication efforts started in earnest around 2007, when I was working toward my PhD at Auburn University; another graduate student came into the office one day and said that her landlord, a local newspaper editor, was looking for columnists. At that time there were not a lot of herpetologists and wildlife biologists talking about science outside of scholarly journals; few folks prioritized the time and effort required to reach new audiences—Whit Gibbons from the Savannah River Ecology Laboratory is a notable exception—but it seemed apparent to me that this

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Whenever I see a thick mess of branches near the water, it is difficult to resist taking some time to look for watersnakes. Forest debris creates hiding spots that allow snakes like this southern watersnake to bask in the sun while also being afforded some protection from predators. Photo by Amanda Hipps.

was an opportunity to get wildlife science in front of a lot of new eyeballs. In part, I wanted people to appreciate the natural world as I did, but I also felt as though there was little point in studying wildlife conservation if few people thought this research was important to put into practice. I reached out to the editor, and he liked my ideas; we agreed that my column would be called “Living Alongside Wildlife.”1 In the early days, my column focused on various field excursions or interesting wildlife tidbits from studies I was conducting; my goal was to give people an inside look into wildlife science while reminding them about the animals that share our landscapes. Because I was not getting paid for this work, I did not feel as though it was worth my while if only

1. An early editorial suggestion for a column title was “Livin’ with Amphibians,” which I felt was a little restrictive and conjured up images of a guy living in the basement surrounded by aquariums full of toads—not that there’s anything wrong with that.

xii : PREFACE

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a few people were reading, so I tried to get more newspapers to run my “Living Alongside Wildlife” essays; eventually they were appearing in three newspapers across Alabama and Georgia. But I still wasn’t satisfied. It seemed as though I would send my columns off and they would disappear into the ether; it was extremely unusual to receive any feedback or even know if anyone was reading them at all. I eventually decided that it made more sense for me to keep the work to myself, so to speak, and put the essays online. This strategy appealed to me in large part because I could respond in real time to any questions or comments people had. In other words, I wanted a blog. In the early days, my blog was hosted on MySpace—perhaps an inauspicious start. But in March 2009 I established www.LivingAlongsideWildlife .com as the standalone site it is now. I uploaded all my old columns and commenced blogging away about various natural history–based anecdotes and stories; each post would get a few dozen views (probably half from friends and family) until July 2009, when I wrote the post that changed everything. There used to be a certain email hoax that herpetologists could expect to receive several times a year as it careened across the country. This email would invariably include a picture of a dead rattlesnake and some outlandish claims regarding its size and the danger it posed. The stories and the purported location would change each year, but the pictures seldom did. Sometimes these hoaxes even took in credulous journalists, and the ridiculous stories would be repeated in news articles or on television. One day, fed up with seeing yet another of these emails doing the rounds, I simply compiled all the usual pictures and put them together in one blog post, tracking down the real story of the pictures when I could and discussing just how big rattlesnakes could actually get (that blog post is adapted here for chapter 20). The post struck a nerve; almost ten years later it is still my most viewed post ever, having been clicked on nearly a million times. I think the popularity of this post can be attributed to two things: first, people receiving the latest email about the giant rattlesnake in the next town over often do an internet search to find out if it is true and end up on my site; second, the many biologists and herpetologists who get asked about these emails over and over can now simply provide a link to my post instead of reinventing the wheel in a new email explaining why the story was a hoax. It could be my imagination, but I think this internet phenomenon has nearly faded away; I update the post when I see a new picture

PREFACE

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pop up, but it has been some time since that has been necessary. Could my blog post have killed this nonsense? A guy can dream. After the post about giant rattlesnakes went viral (relatively speaking), my blog became a known commodity. Today it’s referenced in educational materials and seminars about living with snakes and other reptiles and even cited in scientific papers about how to communicate with people about wildlife. My blogging has slowed down somewhat over the years, but I still view the site as the centerpiece of my outreach efforts. The second big change in my science communication career occurred in July 2012, when I signed up for a Twitter account. At first I thought Twitter would just be another way for people to be informed when new blog posts went live; the account was only set up to automatically tweet updates. But over time I found myself creeping onto the site more and more, jumping into conversations and answering questions about snakes and other creatures. Before I knew it, I was hooked. I am not quite sure how it happened, but by maintaining a consistent presence on Twitter, by finding people with questions about snakes, and by having some fun when I could, I eventually became a “Twitter sensation,” a “genius of hashtag herpetology,” and most famously, “the best biologist on Twitter.”2 Today, thanks to my work on my blog, on Twitter, and on various other websites, I maintain one of the largest public platforms of any wildlife biologist, with a daily audience of tens of thousands of people. Although I am a broadly trained wildlife ecologist, early on I decided I wanted snakes to be the focus of my outreach efforts. Not only was this a group of animals that I knew very well, but snakes are the subject of a disproportionate amount of fascination and misinformation; I really felt they could use some help in the public relations department. I do not, however, view the internet as a megaphone that I can use to broadcast snake trivia; I view it as a tool that affords me the unique opportunity to hear from an audience that does not always get to interact with PhD biologists. After listening to people online for more than a decade, I believe I have unique insights that nobody else has. I know exactly what people want to know about snakes and, critically, what they believe and what they are con2. C. Kenneth Dodd Jr., ed., Reptile Ecology and Conservation: A Handbook of Techniques (Oxford: Oxford University Press, 2016), 439; The Verge, May 2017, https://www.atlasobscura .com/articles/show-wolf-blitzer-turtle-hashtag-herpetology; Slate, May 2015, http://www.slate .com/blogs/wild_things/2015/05/29/snake_science_on_twitter_david_steen_identifies_ photos_as_copperheads_and.html?wpsrc=sh_all_dt_tw_top.

xiv : PREFACE

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A resting but alert copperhead from the northeastern portion of the range for this species. A wide variety of nonvenomous species are often misidentified as copperheads. Photo by Andrew Adams.

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It’s not all about us. Snakes like this western diamond-backed rattlesnake have their own stuff going on; our interactions with them are just brief blips in their long and complex lives. Photo by Bryan D. Hughes, Rattlesnake Solutions.

fused about. I have tried to make sure that this experience and perspective informed every sentence of this book. There are tons of old myths about snakes, like that of the hoop snake (the legendary serpent that supposedly bites its tail and rolls down hills), but nobody has ever asked me about the hoop snake and I don’t think many folks actually believe it’s a real thing. Instead, I hear about rattlesnakes evolving to rattle less (chapter 18), the relative danger of baby snakes (chapter 9), or aggressive cottonmouths chasing people (chapter 19) and dropping into boats (chapter 14). Of all the snakes found within the United States, most of the identification requests sent my way involve only three of them: ratsnakes, Dekay’s brownsnakes, and gophersnakes; they get special attention in the following pages.3 I have learned that herpetologists have not been listening to people 3. Between my blog and Twitter, I have as of September 2018 identified more than five thousand snakes in response to inquiries from people.

xvi : PREFACE

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while they process the information we give them. I think many educators would be surprised to know that much of what we have been doing to help people identify snakes is actually confusing and commonly misunderstood. Frankly, many of the tips and tricks we recite assume a baseline amount of knowledge that often does not actually exist. Red on black, friend of Jack? Depends on where you live (chapter 2)! Can you look at the shape of a snake’s head and tell if it is venomous? Well, I can, but I don’t recommend that you do it (chapter 1). In this book I have tried to explain why many rules of thumb for identifying snakes are misleading or even just plain wrong. In these pages I have tried to answer the most common questions about snakes not just by explaining the relevant biology but by plucking the latest science out of obscure journals and putting it right here. In some cases, I tried to explain how the scientific method has been used to learn more about snakes and what research we still need to do before we can produce an answer to a question in a satisfying way. Sometimes I don’t know the answer! When it comes to snake myths, I have tried to avoid saying that anything is impossible, but I have no problem saying something is inconsistent with what we know about the world. Finally, I provide some helpful tips for those of us who are not necessarily enthusiastic about the snakes around our homes and are looking for environmentally friendly ways of keeping them away (chapter 29). I view this book as the culmination of my science communication efforts, which span more than a decade and have reached hundreds of thousands of people. It is not a comprehensive tome about snake biology nor is it a field guide; rather, each chapter represents a topic that I have learned is important after hearing from you. By the time you have finished this book, I hope I have helped you learn more about the slithering creatures around us, I hope you have gotten a refresher on how scientists answer questions, and, finally and most importantly, I hope I have provided you with ammunition you can use the next time you get into a debate about whether the snake that just fell into your canoe was a cottonmouth.

PREFACE

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acknowledgments

Thank you to the readers of my blog (as well as those who have found me elsewhere), who for more than ten years have asked me questions about wildlife and engaged with me to share their knowledge and stories; you helped me refine my ideas about snakes and learn how I can best share my enthusiasm for them. Thank you especially to the folks who signed up to support my science communication and outreach work when my career was at a crossroads. Your support gave me the flexibility and opportunity to start this book and later transition my outreach activities into a new nonprofit organization, The Alongside Wildlife Foundation. Thank you to Stacy Eisenstark and the rest of the folks at Texas A&M University Press for seeing this book through every step. Two reviewers provided helpful perspectives on the text, as did Harry Greene, who I am also honored to thank for writing the foreword. Any errors or omissions that remain are my fault and my eternal shame. Thank you to the many individuals who contributed photographs for the book; the pictures within these pages have captured the essence of the snakes around us so much more than my words ever could. Critically, they helped me accomplish one of my key goals: to portray snakes as they truly are, not perpetually coiled and ready to strike, but typically sitting silently while camouflaged in a pile of leaves or resting calmly within a stack of rocks. Thank you to Sarah Dahlinger for creating the amazing artwork that introduces each section of this book. Finally, thank you to my mother, who must have been extremely stressed out about my fascination with snakes as a child but encouraged me to explore my interests anyway.

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xx : INTRODUCTION

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PART I IDENTIFYING SNAKES

In this section I have tried to explain everything that is wrong with the conventional wisdom regarding how to identify snakes. Ironically, many of the tips and tricks that people have learned from well-meaning experts are generally flawed when put into practice. For example, how many of us have learned that venomous snakes can be identified by the shape of their triangular heads? But nonvenomous snakes use defensive behaviors to make their heads look triangular! Countless harmless snakes have been sent to their grave thanks to this not-so-helpful tip. Just as frequently, people are told that they can distinguish coralsnakes from nonvenomous mimics by remembering the rhyme “Red on black, friend of Jack / Red on yellow, kill a fellow,” but did you know this tip is meant primarily for distinguishing coralsnakes from a few mimics in the United States and it doesn’t work with all other species or in other countries? Learning the wildlife around us is just like learning anything else: it takes time and dedication and curiosity (often while thumbing through a field guide). But people are always asking me for shortcuts when it comes to identifying snakes, particularly when it comes to distinguishing between venomous and nonvenomous species. I understand why; it is tempting to gravitate toward quick and easy ways to learn. I know we want rules. I know we want to be able to define a venomous snake based on the shape of its head, or the way it swims, or the order of the colored bands on its body. But nature is too complicated and messy for reliable shortcuts. We can talk about general patterns, but these are just rules of thumb and may not even be relevant depending on what snake you are looking at or where you live. I encourage people to stop trying to identify snakes and start learning to recognize them. Let me put it this way: many venomous snakes in the United States happen to have vertical pupils, like a cat, and many harmless snakes have round pupils; however, there are exceptions both ways! A snake does not have a vertical pupil because it is venomous; it happens to have a vertical

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pupil for other reasons. But people saw these broad patterns and tried to make a generalization based on what is often true. As you will read, these generalizations are not rules. I like to make the analogy that recognizing snakes is a lot like recognizing family and friends. You would not measure the length of Uncle Michael’s mustache to figure out who he is or examine the color patterns of Aunt Rochelle’s highlights before you gave her a hug; you just look at them and you know who they are! Identifying animals is similar; once you know them well enough, you can recognize them at a glance. Focusing on specific features may be helpful when you are first learning your snakes, but they should be considered only one step toward achieving the ability to recognize them. Another important thing to consider is that Uncle Michael’s mustache is probably useful for telling him apart from Aunt Rochelle, but it is not a useful tip for distinguishing him from all the other people in the world. It’s the same for snakes: some tips may be useful for distinguishing between two specific species, but that same tip may not be useful for distinguishing a snake from all other species. Unfortunately, many herpetologists and environmental educators have fallen into the trap of trying to offer identification shortcuts. I think this practice is unhelpful if not dangerous to both snakes and people alike!

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1

The Shape of a Snake’s Head Does Not Reveal the Danger

Years ago I was up to my thighs in muddy water, helping lead a class of undergraduates through the murky depths of Chickasawhatchee Swamp in southwestern Georgia to show them some of the unique ecosystems of the region. As you might expect, this southern swamp is a snake paradise, and it wasn’t long before a student straggling behind the group excitedly shouted out that he had found a cottonmouth (Agkistrodon piscivorus), a venomous pitviper not uncommon there. With my adrenaline pumping, I trudged back through the water and followed the student’s enthusiThe watersnakes of North America have a fairly terrible reputation as drab and smelly creatures; to me they are wondrous and diverse (there are currently ten recognized species in the Nerodia genus); many individuals are indeed beautiful once you see them in the right light, like this plain-bellied watersnake. Photo by Matt Moore.

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astic gesturings toward a moss-covered stump sticking out of the muck. There, partially concealed by grass and moss, was a perfectly calm and coiled snake. It was quite beautiful, with large off-white eyes, a coffee-colored back, and a bright orange streak tinged with red starting at its chin and running all the way down its belly. While splashing noises behind me signaled the arrival of the rest of the class, I realized the snake in question was not actually a cottonmouth but a large plain-bellied watersnake (Nerodia erythrogaster), another common but nonvenomous denizen of the swamps in the area. The watersnake was as still as a statue, surely hoping I would soon lose interest and wander off, but I knew it would disappear into the muck in a flash once it realized I was not going anywhere. Because I wanted the rest of students to have a chance to see the snake, I made a grab for it; now, these snakes are quick to defend themselves, and I was tagged several times with rapid bites before I had the reptile safely within my grasp. Snakes within the genus Nerodia have an anticoagulant in their saliva, so blood was immediately running down my hands and forearms and dripping into the water around me. Bloodied but undeterred, I turned around and presented the four-foot-long snake to the group with a flourish and a huge smile. As I looked at their horrified expressions and open mouths, it dawned on me that I hadn’t made clear to them that the initial identification was a mistake. I hurriedly informed that I had been bitten only by a harmless watersnake, not the cottonmouth the student had been yelling about. They were visibly relieved. People have struggled to distinguish venomous snakes from harmless species forever. As a result, a ton of tips have emerged to help folks figure out who’s who. Just about everyone has heard this one: if a snake has a triangle- or diamond-shaped head, it is venomous. Many environmental educators use this line when they are teaching people how to recognize dangerous snakes around their home. Teachers and professors say it too when they are telling their students how to identify venomous snakes. So, what’s the problem? It is wrong. Identifying a snake just by looking at the shape of its head does not work. Here’s the thing. If you have seen a lot of snakes and are really good at identifying these animals, then you probably have no problem recognizing that vipers do have a characteristic and relatively triangular head shape. But herpetologists need to be honest about how we identify snakes. People who know snakes well use their overall impression of the animal to deter-

4 : IDENTIFYING SNAKES

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Many nonvenomous snakes, like this plain-bellied watersnake, will flatten out their bodies and necks and assume a defensive posture when they are afraid; this strategy results in their heads looking quite triangular. Photo by Dirk J. Stevenson.

mine the species; specific features like a snake’s head shape only come into consideration when we are not confident in our identification. For example, if someone gave me a poor-quality photograph and I had trouble recognizing the snake, then I might start looking at specific parts of the animal to try to narrow down what species I could be looking at. Generally speaking, though, if I see someone ticking off a list of distinguishing features as they try to identify a snake, then I know that person is a rookie. Anyway, back to head shape. There are a number of problems with using head shape to determine if a snake is dangerous. Most snakes have a head and jaw structure that is at least vaguely triangular just because of basic snake morphology. Snakes have vertebrae, ribs, and a skull, and they give the animal its shape. Even though a snake doesn’t have legs doesn’t mean it’s just a tube with a mouth! Many people who encounter an unidentified snake in their yard have not spent a lot of time looking at snakes, and without that experience

THE SHAPE OF A SNAKE’S HEAD DOES NOT REVEAL THE DANGER

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Although we are often told that venomous snakes have triangular heads, this shape is not always apparent, even for some pitvipers like this eastern massasauga. Photo by Nick Scobel.

it is very easy to imagine any snake’s head as one that is triangle-shaped. Cornsnakes and racers have some of the least triangular heads that a snake could possibly have. Yet, people frequently kill these animals because of their perceived head shape. If people consider these species to have triangle-shaped heads, they could do the same for any snake in the world. And that means using head shape to determine if a snake is venomous is a tip that is just no good. The reverse is true as well: several people have showed me pictures of cottonmouths and were surprised to learn their identity. “But their heads did not look triangular,” they said to me. That’s scary; I wonder if anyone has been bitten by a venomous snake because of this myth. As if identifying snakes based on their head shape wasn’t hard enough, many completely harmless snakes actually flatten their head (and often

6 : IDENTIFYING SNAKES

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This southern watersnake is feeling particularly defensive, and for that reason it is engaged in a display that results in a triangle-shaped head. This snake is not venomous. Presumably a triangle-shaped head reduces predation, but we have limited evidence to evaluate this idea. Photo by Dirk J. Stevenson.

the rest of their body) when they are feeling threatened, which temporarily makes their head look more triangle-shaped! One reason they might do that is so that potential predators think the snake is venomous and leave it alone. Hog-nosed snakes and watersnakes are famous for this defensive strategy. This doesn’t make them dangerous. Another problem is that by stressing the notion that snakes with triangular heads are venomous, it is possible for people to forget that this “rule” applies only to vipers. Snakes within the Elapidae family (cobras and coralsnakes are in this family) are also venomous but don’t have a triangle-shaped head at all! I hope nobody decides to pet a cobra because they do not see anything wrong with the shape of its head.

THE SHAPE OF A SNAKE’S HEAD DOES NOT REVEAL THE DANGER

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CAN YOU IDENTIFY A SNAKE FROM ITS SHED SKIN? The body shape and position of a snake, as well as its color and patterning, help create an overall feel (i.e., a gestalt), and that is usually what herpetologists use to identify them (often together with some information about where a particular snake was found). A white, flattened, and crinkled snakeskin that one may find in the yard or in the rafters of an attic does not often have that unique “feel” that actual snakes do, so the process of identification is different and more technical. But yes, it is possible. If I have a snakeskin in my hand, the first thing I do is check for any faint patterns or unique morphological features, like the upturned snout possessed by hog-nosed snakes. But I am seldom this lucky. The next step is to see if each scale has a keel (i.e., a slight ridge running down the center) because this is easy to determine and often eliminates a lot of species from consideration. Then, I can look for the presence and arrangement of specific scales (but I need a technical book or dichotomous key for help because I have never tried to memorize this aspect of snake biology). This study of the scales allows me to continue the process of narrowing down the list of suspects, taking into account the general size of the skin and my knowledge regarding what snakes live in the area. So, when people send me blurry pictures of a snakeskin with no location information and ask me what kind of snake it is from, I will generally just tell them that I appreciate their confidence in my skills but am unable to help them at this time.

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Are Snakes with Red on Black Truly a Friend of Jack?

It can be an intimidating experience to live around lots of snakes but not know which are venomous. It is no wonder that lots of tricks have emerged to help people learn about these creatures. You’ve probably heard this one: “Red on black, friend of Jack / Red on yellow, kill a fellow.” But what do you really know about it? The coralsnake is an iconic animal, and just everybody knows that you do not want to get bitten by one. This venomous species is different from pitvipers like copperheads and rattlesnakes because its venom is primarily neurotoxic, and thus largely affects our nervous system, and not hemotoxic, which would primarily affect our blood and tissues. In any case, this “Red on black” rhyme was designed to allow people to quickly and easily differentiate between the coralsnakes in the United States (there are currently three different species of coralsnakes recognized in the United States) and other species that look superficially similar. Basically, coralsnakes in the United States have a unique pattern of bands along their body; the red and the yellow bands touch each other, but the red and black bands do not. I need to make something clear right off the bat. You may have noticed that I qualified my statements above by saying I was talking about coralsnakes in the United States. In addition to the three species of that snake in this country, there are other species of coralsnakes found throughout Central and South America, and guess what? They look different from the ones that live in the United States. Do you see where I am going with this? Using this rhyme to identify coralsnakes in other countries could get you hurt or killed because you can indeed find some venomous ones with red and black bands touching. I think pretty much every herpetologist I know has heard a story about a tourist who bravely (but with misplaced confidence) picked up a potentially deadly coralsnake because of this rhyme. Clearly, we need to add some more precision to our rhyme. How about, “Red on black, friend of Jack / Red on yellow, kill a fellow / Traveling abroad? This rhyme’s a fraud”? I don’t know; you can probably come up with something better.

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This beautiful harlequin coralsnake allows us to clearly see the order of red, yellow, and black bands that are typical for this species. Red is touching yellow, and this is indeed a venomous snake. This species largely eats other reptiles, including small snakes and lizards. Photo by Nick Scobel.

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For the most part the rhyme works pretty well in the United States when one wants some help differentiating between coralsnakes and species that are considered coralsnake mimics, including scarletsnakes (Cemophora coccinea) and a number of different types of kingsnakes. You see, the bold patterning of a coralsnake is considered aposematic coloration; basically, this serves as a warning to potential predators that they may regret an attack because they could get a bite from a venomous snake in return. What the mimics have done is called Batesian mimicry; even though they are harmless, they evolved a pattern of bands similar to those of the venomous species because predators tended to avoid the animals that looked like coralsnakes. Over many years, the snakes with bold patterning passed on their genes to their offspring, and that is why they look the way they do today. But evolution is not a perfect process, and the harmless snakes look different enough from the real deal that you and I can often quickly tell them apart. I suspect that the original rhyme emerged long ago in the southeastern United States and served a purpose in that region for many years. But then, as this nation’s infrastructure improved and technology advanced, the rhyme and small piece of local ecological knowledge became disassociated from that place of origin and started popping up where it did not work This harlequin coralsnake from Florida has a slightly messier pattern than the snake pictured earlier. There are clearly black flecks within the red bands. Photo by Noah K. Fields.

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The “red on black” rhyme is useful for distinguishing coralsnakes in North America from a few specific species that mimic them in the southeastern United States. I sometimes see this rhyme inappropriately used to help identify various other species, like this cornsnake, with mixed success. Photo by David Steen.

as well. For example, pity the poor shovel-nosed snakes of the southwestern United States, for they do have red and yellow bands that touch each other. One can only imagine how many have been killed after being mistaken for a coralsnake. I guess we need to revise our rhyme again: “Red on black, friend of Jack / Red on yellow, kill a fellow / Traveling abroad? This rhyme’s a fraud / Some exceptions you should make / If only for the poor shovel-nosed snake’s sake.” I think this is getting a little tough to remember. I often say that tips, tricks, and rhymes may be useful for helping people just starting out learning their snakes but should not be used as the sole means of identifying species. The coralsnake rhyme is another good example why. Some people think that this rhyme is a universal truth about snakes instead of just a trick that can be used to help differentiate coralsnakes in the United States from a handful of specific mimics; I have seen people look at the shapes, colors, and patterns of other snakes, like cornsnakes, and try to use the rhyme to identify them. I don’t even know what conclusion you might come to if you tried that. It is also important to remember that weird genetic anomalies do show up in nature from time to time, including albinos and melanistic (completely black) snakes or snakes with weird patterns; this includes coralsnakes. I will let you figure out how we should modify the rhyme to incorporate that.

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What Is the Difference between a Cottonmouth and a Water Moccasin?

Sometimes people write to me asking if I can please tell them the difference between a cottonmouth and a water moccasin. This is a trickier question than it seems. It is generally well understood that all species that have been officially discovered, recognized, and described are given a scientific name. These scientific names are made up of two Latin words representing their genus and species. For example, the scientific name of the northern cottonmouth is Agkistrodon piscivorus. This name tells us that this animal is in the genus Agkistrodon (along with some other closely related snakes), and it is the species piscivorus (a name this snake does not share with anything else in that genus). The scientific name of the eastern copperhead is Agkistrodon contortrix. This means that copperheads and cottonmouths are in the same genus (i.e., they are closely related) but are different species. Common names, on the other hand, are a different story because there are not really any hard-and-fast rules about them. When I say common names, I mean the words we use to refer to a species in casual conversation. Both copperhead and cottonmouth are common names. You can imagine that, depending on where you are and because there are no rules about common names, different people might refer to the same species with different common names. Things can get even more confusing when multiple species are referred to by the same common name. For example, what comes to mind when I say “black snake”? Depending on where you are from, you may be imagining a North American racer (Coluber constrictor), an eastern ratsnake (Pantherophis alleghaniensis), an eastern black kingsnake (Lampropeltis nigra), or even an eastern indigo snake (Drymarchon couperi). Like I said, these things can get tricky and confusing. But common names can be fun because many of them are quite colorful, like swamp lion (apparently this is sometimes used for cottonmouths), and it is neat to learn which names are used in different areas; I think it helps us understand regional differences in how we relate to our natural heritage.

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The lack of rules regarding common names makes it quite difficult to answer technical questions about them. That said, the Society for the Study of Amphibians and Reptiles, an organization made up largely of professional herpetologists, does publish a continuously updated list of standard common and scientific names, but I do not expect everyone to be familiar with their rules and guidelines. On their list you will not be able to find an animal with water moccasin as its name. The cottonmouth reigns supreme and alone as the only aquatic pitviper in the swamps of the southeastern United States. However, I need to qualify this somewhat: a 2015 study of cottonmouth genetics argued that what we have been calling the cottonmouth is actually two different species (same for the copperhead).1 Although these two species of cottonmouths interbreed and exchange genes readily, there has to be some kind of boundary between them (otherwise it would not make sense to argue they are separate species), so you would not find both within the same place. If people say water moccasin when they are referring to a venomous snake that lives in the waters of the southeastern and midwestern United States, they are thinking of a cottonmouth. However, sometimes people say water moccasin (or just moccasin) when they are referring to a nonvenomous snake that lives in the water; in these cases it is generally safe Rain is not particularly intimidating to snakes that spend much of their time in the water, like this cottonmouth. For snakes that eat frogs, rain can be quite beneficial, as the weather may inspire the amphibians to focus on singing and finding mates at the expense of staying vigilant against potential predators. Photo by Nick Scobel.

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Any snake near water, including this southern watersnake, runs a high risk of being misidentified as a venomous cottonmouth. Photo by Matt Moore.

to assume they are thinking of a watersnake within the genus Nerodia and not a cottonmouth. Much confusion can be averted by using the word moccasin only when speaking of the venomous cottonmouth (or not at all). Some people believe there are multiple kinds of cottonmouths in the same place. However, there is no scientific evidence to support this idea. So what could cause someone to think this? It is true that the species is sexually dimorphic (this means that males and females look different in some way). However, the sexual dimorphism in cottonmouths is just body size (males can get larger than females), so I do not think that is enough to mistake them for two species. When they are young, cottonmouths have a bright yellow or green tail that they use to attract prey. Adults do not. Young snakes are also often more brightly colored than adults, which can appear quite dark and drab. Perhaps the differences between young and adult cottonmouths are significant enough to convince some people that they are actually different species? A brightly colored young cottonmouth can be quite a surprise. I once saw a young cottonmouth that was so vivid and distinctly patterned that it took a long time to convince myself that I wasn’t actually looking at a copperhead! So how does one tell the difference between cottonmouths and copperheads? Read on.

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How Can You Tell a Copperhead from a Cottonmouth?

Cottonmouths and copperheads are closely related venomous snakes that are frequently encountered in the United States. Recently published genetic evidence has led some scientists to conclude there are actually two species of cottonmouths and two species of copperheads (if you ask me, I do not particularly feel that there has been sufficient scientific or philosophical evidence to consider this case settled). But, whether you consider a cottonmouth a single species or two, they pretty much all look and act alike, so it’s easy to generalize (same for copperheads). Because cottonmouths and copperheads may seem similar at first glance, they are often confused for one another. What makes things particularly interesting is that many people do not know they have a problem distinguishing them, so confident are they in their identification skills. But the differences between these animals can be pretty easy to notice if you know what to look for (and what to ignore). So, here are my top five tips for determining whether the snake you found is a cottonmouth or a copperhead. Remember, there are very few hard-and-fast rules that can be used to definitively identify a snake; I rarely tell people that they can use a tip to recognize snakes, but knowing typical characteristics can help everyone get on the same path to snake enlightenment. 1. Cottonmouths have white mouths. Cottonmouths do not want to bite you unless they really they have to. That is why they’ve come up with some impressive defensive displays. The point of these defensive displays is to scare off predators before a bite is necessary. Fortunately, one of the most common displays offers a great opportunity for differentiating cottonmouths from copperheads. When threatened, cottonmouths will often open up their mouths wide and show off their namesake white mouth (they are called cottonmouths for a reason, after all). Copperheads can open their mouths too, but they do so less often and their mouths are more pinkish. We can’t always use this feature to tell them apart because

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A cottonmouth on land is likely to feel quite vulnerable when approached by a potential predator, and this individual from Oklahoma is showing off its characteristic white mouth to discourage people or other animals from approaching any closer. Photo by Noah K. Fields.

cottonmouths do not always open their mouth, and I do not suggest you try very hard to convince one to do so. And, to be honest, some cottonmouths have a relatively pink mouth too. 2. The color and patterning of a cottonmouth’s body are different from those of copperheads. Some folks more creative than I am have described adult copperheads as being the color of chocolate milk with a Hershey Kiss pattern. I think that’s a great analogy. Many copperheads are indeed this color, with a brown hourglass-banding pattern. It is important to note, though, that some copperheads may appear a little more brown or a little more orange, depending on the individual and where it was found. Also, copperheads in the western portion of their range tend to have relatively broad bands that do not look much like Hershey Kisses at all.

HOW CAN YOU TELL A COPPERHEAD FROM A COTTONMOUTH? :

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Copperheads are often said to have a pattern of bands that look like Hershey Kisses, but in the western portion of their geographic range these bands can appear quite broad, as seen in this individual from Texas. Photo by Noah K. Fields.

Adult cottonmouths, on the other hand, often appear almost black or dark brown, much different than adult copperheads. However, some cottonmouths are not so dark that you can’t make out a pattern. Cottonmouth patterns are superficially similar to those of copperheads, but the hourglass bands of a cottonmouth are not as precise as those of copperheads: they are messy, the lines are blurred, and sometimes there are other shapes thrown in there as well. Now, if you look at copperheads from Tennessee, Kentucky, western North Carolina, and surrounding regions, you may notice that their hourglass patterns are not quite as precise as you might expect. The borders might be a little ragged, or you might see some spots within the Hershey Kisses. But now we come to an important clarification: baby cottonmouths don’t look like adult cottonmouths, while copperheads look more or less the same over their entire lifespan. Baby cottonmouths are as strikingly and vividly patterned as copperheads, and this is the life stage when people are most likely to confuse the two species. Just because the patterns on a baby Agkistrodon are clear and precise does not mean it is a copperhead. This is where it’s important to see if the hourglasses are messy or not. Again, copperhead bands tend to be relatively crisp; cottonmouth bands are not. Both cottonmouths and copperheads have a bright yellow or green

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Older cottonmouths often appear relatively dark and without much of a visible pattern, but they certainly are not born that way. This age variation leads many people to confuse young cottonmouths for copperheads, which tend to retain their bold pattern throughout their lives. Photo by Nick Scobel.

tail tip when they are babies (they use it to lure prey), so the presence of this bright tail tip cannot be used to differentiate between the species. The tails of many copperheads in the western portion of their range actually have a greenish color to them even after they become adults. 3. Cottonmouths have a dark band on their face that runs through their eye; copperheads generally do not. Take a look at the pictures in this chapter and you will see what I mean. 4. In many parts of the country you can find cottonmouths or copperheads, but not both. In many parts of the Southeast and Midwest of the United States, both cottonmouths and copperheads can be found, in general. But there are lots of places where only one of the two occurs. For example, cottonmouths can be found throughout all of Florida, but copperheads only live around one small bit of the Panhandle. On the other hand,

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Here is a fairly typical copperhead in appearance and behavior. Notice the lack of a dark band on its face; this can be helpful in distinguishing copperheads from cottonmouths. Photo by Andrew Adams.

copperheads are crawling around much of the northeastern United States, but if you are traveling up the East Coast from Florida you will see your last cottonmouth in Virginia. 5. Copperheads and cottonmouths are usually found in different ­ abitats. h Cottonmouths mostly spend time in wet and/or swampy areas, while copperheads prefer more upland and forested habitats. This isn’t a hard-and-fast rule, though, so it should be used together with the other tips provided here. Cottonmouths may migrate out of their swamps when the water dries up, and I have seen cottonmouths suddenly appear in new wetlands formed by recent rains; they must have gotten there by crawling on land. I have never seen a copperhead in the water, though; my guess is that it is a very rare occurrence. People try to prove me wrong about this all the time, but their pictures usually end up being of common watersnakes (Nerodia sipedon).

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Is This a Black Snake?

What kind of snake is this? People send me tweets and emails all the time asking me what kind of snake they just found. You might think that a snake expert could easily answer these questions. But the more I learn about snakes, the harder it is for me to figure out what to call them. It is fairly common to see news articles about scientists discovering new species. These announcements generally come after a scientific journal publishes a research paper describing how scientists differentiated their species from all the other species we already knew about. This process typically includes detailing what the species looks like or how its genetics are unique (or both). There are a couple of things wrong with how these types of stories are often framed. First of all, what did the scientists really discover? Ask most

In many portions of their range, North American racers appear quite black (although note their white chins). Naturally, many people call them black snakes. This often leads to considerable confusion because there are a number of other species that appear almost entirely black as well. Photo by Breanna Ondich.