Sistrurus Catenatus) in Colorado
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UNIVERSITY OF NORTHERN COLORADO Greeley, Colorado The Graduate School THE MASSASAUGA RATTLESNAKE (SISTRURUS CATENATUS) IN COLORADO A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Arts Justin Peter Hobert College of Arts and Sciences Department of Biological Sciences August, 1997 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. © 1997 JUSTIN PETER HOBERT ALL RIGHTS RESERVED Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. THESIS COMMITTEE: *THESIS SPONSOR (Stephen P. Mackessy, PhTD.) (William. E. Harmon, Ph.D.) (David Chiszar, Phdj.) DEAN OF THE GRADUATE SCHOOL yle R. Carter, Ph.D.) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ABSTRACT Hobert, Justin Peter. The massasauga rattlesnake (Sistrurus catenatus) in Colorado. Published Master of Arts Thesis, University of Northern Colorado, 1997. The massasauga rattlesnake, Sistrurus catenatus, is currently considered a species of special concern by the Colorado Division of Wildlife. From. July, 1994 to October, 1996, 255 massasaugas were captured or recovered from 11 counties in Colorado. Life history and distribution were investigated for the massasauga in Colorado, including an analysis of the distribution pattern and habitat characteristics at sites of capture and recovery. Information gathered included trends in population size and abundance, areal vegetative analysis, seasonal/temporal activity patterns, reproduction, and prey and predators. This study also investigated the morphological variation of the massasauga from Colorado and an evaluation of its current taxonomic status relative to S. c. edwardsi and S. c. tergeminus, the neighboring subspecies. Morphometric characters from samples from each group were measured and examined for diagnostic reasons. Scale counts on 18 areas of the body were examined for 268 snakes from Colorado, 72 edwardsi from Arizona and New Mexico, and 35 tergeminus from Kansas. Distribution, habitat and life history characteristics, iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. along with color and size, were also used to evaluate the taxonomic status of the massasauga in Colorado relative to the other described subspecies. Distribution results indicated that the population of massasaugas in Colorado is disjunct from the neighboring populations and is a dry, arid grassland species which occupies, short-grass/sand- sage prairie, an increasingly uncommon habitat. The massasauga is nocturnal in summer in Colorado and feeds mainly on lizards as juveniles and small rodents as adults. Young are bom late summer to early fall (one clutch size of 5). Specific scale counts showed that the Colorado population is more closely related to the desert subspecies (S. c. edwardsi ) than it is to the western subspecies (S. c. tergeminus). Of the Colorado massasaugas examined, 79% had 23 scale rows at mid-body; while S. c. edwardsi also had a frequency of 79%. Sistrurus. c. tergeminus often had 25 (88%). Size and ground color were similar for Colorado snakes and S. c. edwardsi, while S. c. tergeminus were much larger and darker. The morphometric and habitat data support the conclusion that massasaugas in Colorado should be designated as the desert subspecies, S. c. edwardsi, not as an intergrade. iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGMENTS This project would have been nonexistent if not for the generosity and encouragement of the Great Outdoors Colorado program and the Colorado Division of Wildlife, especially, Judy Sheppard, Chuck Loeffler, and Tom Nesler. Special thanks go to my advisor, Dr. Steve Mackessy, for his instrumental support and fortitude throughout this project, and working with me to become a better writer. I am indebted to Dr. William Harmon for his guidance and influence he has so constantly provided for me and others. His companionship and friendship have been a requisite. I would also like to thank Dr. David Chiszar for assisting me through the understanding of statistics and introducing me to Dr. Hobart M. Smith who also provided valuable input and advice for this project. Lauren Livo, Geoff Hammerson and Andrew Hoiycross provided information and specimens for which I am thankful. Thanks go to the Kansas Department of Wildlife and Parks for permission to search for snakes at Cheyenne Bottoms National Wildlife Refuge. v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Distinctive gratitude goes to Dr. James Fitzgerald for his vital input and fellowship which motivated me and were critical throughout my graduate career Much of this project would not have been as true and enjoyable without the companionship and hard work of Chad Montgomery, Ron Donoho, Enoch Bergman, Scott Boback, Kevin Waldron, and Ben Hill who literally logged thousands of miles with me looking for herps. For Tim Hugo, Brandon Quinn, Jennifer Mauch, Robert Hill and Dr. Jennifer Clarke I am thankful for their assistance in the field. Many people from southeastern Colorado allowed me to search and set traps for critters on their land and I thank them for their willingness to work with me. The Palmer Family in Lincoln County have been more than accommodating and neighborly and my appreciation for them is immeasurable. I am especially thankful and lucky to have the friendship and encouragement of my past and present fellow graduate students who have been an integral part of my understanding and awareness of the fascinating field of Biology. I eminently want to thank Keri A. Fox for her companionship, moral support, encouragement, and understanding. Her kind patience, dedication, and influence have been a boundless help throughout my field experiences. vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Finally, I wish to pass my grand gratitude to my parents for their love and support. Everything I have, and have learned, I owe to them. To my brothers and sisters and Smith, I dedicate this thesis. vii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION..........................................................................1 II. DISTRIBUTION AND LIFE HISTORY OF THE MASSASAUGA IN COLORADO Introduction. ..............................................................................14 Materials and Methods ...........................................................16 Results......................................................................................23 Discussion ................................................................................63 III. MORPHOLOGICAL VARIATION AND TAXONOMIC STATUS OF THE MASSASAUGA IN COLORADO Introduction ............................................................................. 77 Materials and Methods ...........................................................79 Results ................................................................................83 Discussion ................................................................................94 IV. CONCLUSION...........................................................................98 LITERATURE CITED..............................................................106 APPENDICES.......................................................................... 112 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES TABLE PAGE 1. Total search efforts (estimated) for S. catenatus by- county in Colorado (1994-1996) .............................................23 2. Species of reptiles and amphibians seen at areas where 10 or more S. catenatus were found .......................... 28 3. Total number of S. catenatus for each surveyed county (1994-spring, 1997) ..................................................................31 4. Comparative body measurements of adult male and female S. catenatus from Colorado ........................................ 47 5. Number and proportion of S. catenatus captured or above ground at specific temperatures.................................49 6. Number of S. catenatus observed or collected by month (1994-1996).............................................................................. 50 7. Number of live S. catenatus captured in Colorado by time of day and by month (1994-1996) ................................. 50 8. Capture and recapture data for PIT-tagged S. catenatus in Lincoln County, Colorado ..................................................54 9. Prey identified in fecal material or gut contents of S. catenatus from Colorado ......................................................... 60 10. Comparison of coloration for S. catenatus from Colorado, New Mexico and Arizona (edwardsi), and from Kansas (tergeminus).............................................................................. 85 11. Meristic and mensural comparisons of samples of S. catenatus from Colorado, Arizona and New Mexico (S. c. edwardsi) and Kansas (S. c. tergeminus).....................88 ix Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE PAGE 12. Student’s t-tests of paired means comparison of scale counts between S. catenatus