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A Field Guide to the Amphibians and Reptiles of Wyoming

A Field Guide to the Amphibians and Reptiles of Wyoming


Copyright © 2011, 2017
by Dan Lewis.

Photographs copyright © 2011, 2017
by Dan Lewis.

ISBN: 978-1-936870-02-8.

Published by The Wyoming Naturalist
Douglas, WY 82633

All rights Reserved. No part of this book may
be reproduced in any form or by any electronic
or mechanical means including information storage and retrieval systems without
permission in writing by the author.

Permission to use images of the following species was generously granted and the copyright remains with the individual:

Great Basin Skink © Leslie Schreiber

Great Basin Skink © Charlotte Matthews

Desert Striped Whipsnake © Deborah Ambrose

Plains Black-headed Snake © Gary Nafis




Amphibians and Reptiles of Wyoming by George T. Baxter and Michael D. Stone was first published in 1980 and a second edition was published in 1985. Regrettably, the book was allowed to go out of print. I was privileged to have had Dr. Baxter as my major professor at the University of Wyoming when I was working on a master's degree investigating the demise of the Wyoming Toad. George passed on a few years ago. I was also fortunate to have worked with Mike during my first herpetological field study in Sweetwater County. This guide was written with great appreciation and respect for these two individuals.

George, I hope you're smiling!


From The Desert Year by Joseph Wood Krutch.

Like all the spadefoots, he is a great digger with his hind legs and he is conveniently distinguished from all the Bufos (the genus to which the common garden toad belongs) by the fact that the contracted pupil of his eye is vertical like a cat’s, not round or horizontal like that of the Bufos.

There is, then, no trouble about naming him, but the available information does not go much beyond that. He is believed to mate only once a year and always after a summer rain. At other periods he has been accidentally dug up of the earth. But in what sort of pool does he successfully raise his family? How much of the time does he remain buried? Does he come out to eat occasionally during the almost year-long period when he is rarely if ever seen? Finally, how does he like the extraordinary existence which he seems to lead? On these questions, the books cover their silence with the air of not having the space to go in for that sort of thing. Queried face to face, the authorities shrug their shoulders: “Wish I knew.”


It is no passing afterthought to give my thanks. These good people helped strengthen my voice and lessen my fear.

I thank Ken Grant for the many discussions during the development of this guide; from the width of the path to the point of the pen, they were crucial to its completion. I thank Zack Walker for reviewing the manuscript, for his valued updates to the distribution maps, and for helping me pull together key elements during the final stages.

I am happy to thank: Annie Bergman, Brent Graves, Diane Harrop, Paul Kuecks, and Mike Stone. Their time and careful attention during the review and revision process was wonderful and greatly appreciated.

Thanks to Deborah Ambrose, Charlotte Matthews, and Leslie Schreiber for allowing me to use their images of the two new species of reptiles in Wyoming, the Great Basin Skink and Desert Striped Whipsnake. I also thank Gary Nafis for allowing me to use his images of the Plains Black-headed Snake. Thanks to Charlie Plymale for his assistance with photographing the Pale Milksnake and Northern Rubber Boa. I thank Rick Kilmer for his help scanning my old film images and converting them to digital format.


The purpose, scope, and narrative style of this guide are directed toward the layperson and amateur herpetologist. If you are interested in a more technical source of information on the amphibians and reptiles found in the Rocky Mountains, I recommend the guide to Colorado by Hammerson or the guide to New Mexico by Degenhart et al (please see the bibliography). Both of these excellent books provide detailed accounts of herpetology in those states. Perhaps more importantly to the novice or student, I believe they will benefit the reader by helping to instill an appreciation for the flavor of good technical writing with the laborious and passionate manner in which they share their insight and scientific expertise—they take their time to be deliberate and exact. In addition, if the appropriate resources are available to you, I also suggest reading some of the original research journals and publications cited in these two guides. It is these original studies conducted by dedicated researchers that not only drive the scientific community but they provide the core foundation from which derivative works by other authors are made available to the general public.

The methods used to find amphibians and reptiles are standard: drive roads at night looking for animals crossing or warming themselves on the surface, drive roads or walk the margins of suitable habitat listening for breeding calls, search suitable habitat turning over rocks, boards, logs, and other surface material used as cover, walk suitable habitat looking for the animal directly as it interacts with its environment. Capturing the animal is done by: dip-netting for larvae, noosing using a small pole or rod with an attached string or thread with a slip-knot (I prefer waxed dental floss.), carefully hooking or pressing the animal using a “snake stick” and directly by hand with the probability of being urinated or defecated on and bitten.

I won’t pull a punch here—part of the fun of working with amphibians and reptiles is that you often get a chance to hold the creature in your hand and that can be a wonderful thing. There certainly are times when direct contact with one of these animals is illegal (endangered species), dangerous (venomous rattlesnakes), or otherwise inappropriate (during mating) and it may always be politically incorrect. It will always be better for the animal if you observe or photograph from a short distance using close-focusing binoculars or telephoto lens. But if you do choose to make contact, you must really THINK about the stress the animal will be subjected to and you must really have RESPECT for the welfare of the animal. Carefully support the animal to provide some sense of security, keep it cool or its skin moist so that it does not overheat or dry, and quickly release it by returning it back to the same place where it was found. Avoid the urge to bring the specimen home and keep it captive. Don’t transport the animal to a different location for release because you will increase the possibility of spreading disease and you will decrease the survivability of the animal by placing it in unfamiliar surroundings.

I would be remiss if I failed to include these thoughts. Historically, many amphibians and reptiles have had a difficult time living alongside humans. To some extent, frogs seem to lie just outside the wrath and prejudices of mankind; salamanders, newts, and toads are less able to escape intolerances, presumably because of their secretive nature or warty appearance. Turtles and lizards are often (but not always) excluded from narrow-mindedness. It is the snakes that receive the brunt of man’s misconceptions and torment. I hope the readers of this guide will be able to help educate—and admonish where appropriate—the perpetrators of unkind acts to these creatures.

The amphibians played an important role in the evolution of vertebrates and the transition from an aquatic to terrestrial lifestyle. For most amphibians, their reproductive efforts are still tightly linked to a watery world: external fertilization and embryonic development still necessitate an aquatic environment. It is through their metamorphic change, from a larval stage to the adult body form, that they are able to gain a degree of independence and move on to land and thrive. The reptiles continued to make evolutionary advances giving them greater aquatic independence and enabling them to invade deeper into the terrestrial environment and obtain a more widespread distribution. The improvements of internal fertilization, development of the amniotic egg, and the utilization of scales to provide a more robust and watertight barrier all contributed greatly to the success of the reptile’s invasion on to land. By keeping in mind the unique and fundamental adaptations these amphibians and reptiles have undergone, you will be able to nurture a better understanding and a kinder appreciation of their struggle for life.

Species Accounts



Family Ambystomatidae


Family Scaphiopodidae—Pelobatidae


Family Bufonidae


Family Hylidae

Family Ranidae




Family Chelydridae

Eastern (Common) Snapping TurtleChelydra serpentina serpentina

Family Emydidae

Family Trionychidae


Family Phrynosomatidae

Family Scincidae

Family Teidae


Family Boidae

Family Colubridae

Family Dipsadidae

Family Natricidae

Family Crotalidae