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Constriction Behavior, a Key Innovation in Snake Evolution: the Integration of Ethology and Physiology

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Constriction Behavior, a Key Innovation in Snake Evolution: the Integration of Ethology and Physiology University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 5-2005 Constriction Behavior, a Key Innovation In Snake Evolution: The Integration of Ethology and Physiology Rita S. Mehta University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Psychology Commons Recommended Citation Mehta, Rita S., "Constriction Behavior, a Key Innovation In Snake Evolution: The Integration of Ethology and Physiology. " PhD diss., University of Tennessee, 2005. https://trace.tennessee.edu/utk_graddiss/2262 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Rita S. Mehta entitled "Constriction Behavior, a Key Innovation In Snake Evolution: The Integration of Ethology and Physiology." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Psychology. Gordon M. Burghardt, Major Professor We have read this dissertation and recommend its acceptance: Marguerite Butler, Todd_Freeberg, Neil Greenberg, Richard Saudargas Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a dissertation written by Rita S. Mehta entitled “Constriction Behavior, a Key Innovation In Snake Evolution: The Integration of Ethology and Physiology.” I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, with a major in Psychology. Gordon M. Burghardt Major Professor We have read this dissertation and recommend its acceptance: Marguerite Butler____________ Todd_Freeberg______________ Neil Greenberg______________ Richard Saudargas___________ Accepted for the Council: ___Anne_Mayhew______ Vice Chancellor and Dean of Graduate Studies (Original signatures are on file with student records.) Constriction Behavior, a Key Innovation in Snake Evolution: The Integration of Ethology and Physiology A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Rita S. Mehta May 2005 Copyright © 2005 by Rita S. Mehta All rights reserved ii ACKNOWLEDGEMENTS In each Part (Part 1: Introduction excluded) I acknowledge the people who helped me in many ways. In addition to help with the individual projects, I received invaluable help and inspiration throughout my education from several people, many of whom contributed to the specific projects. I am grateful to my advisor Gordon Burghardt. Gordon Burghardt was the reason I came to Tennessee. I would also like to thank the members of my committee, Marguerite Butler, Todd Freeberg, Neil Greenberg and Richard Saudargas for their support, guidance and encouragement. Jim Hall also helped review proposals and always provided insightful comments. I am most indebted to Brad Moon for allowing me to study muscle physiology in his laboratory. Without Brad’s help, this dissertation would not have been as interesting. Brad’s immense support and instruction with EMG experiments as well as our conversations about constriction behavior in snakes enabled me to better understand the importance of combining physiology with behavior. I made many trips to conduct EMG experiments at the University of Louisiana. During these trips I was invited to sit in on valuable graduate student seminars and was also given an outlet to present my work. Bob Jaeger always made it a point to try and touch basis with me and talk to me about “the next step” in my research career. Ali Rabatsky not only provided much help during experiments but her friendship has been invaluable. I sincerely thank Kate Wadsworth for welcoming me and giving me a comfortable and enjoyable place to stay while visiting Lafayette, Louisiana. I would especially like to acknowledge Tracy and David Barker, Brad Moon and Brian Ott. These individuals provided the animals used in this study. Tracy and David iii also helped me develop a better understanding of snake behavior. The summer I spent with them has been one of my most valuable and memorable research experiences. Little did I know that all those late night conversations with Tracy would help me formulate both my masters and doctoral research. Brian Ott, on more than one occasion, allowed me to photograph snakes from his personal collection as well as the collection at the University of Alabama. Brian was also enthusiastic and great to talk to about snake feeding biology. There are many other people I would like to thank: Marguerite Butler for her helpful insight and encouragement, Karen Davis and Lauren Kirby for being excellent lab mates and friends and for covering my classes while I was in Louisiana. Sarah Connor, Laurianne Hebb, and Ellen Mahurin made my experience in the program more fun. Catherine Mc. Millen helped me build the spectacular plexi glass feeding arena used during my stimulus control experiments in Part 2. Dr. David and Sharon Kirby loaned me their family Hi-8mm video recorder when mine broke so I could continue to collect videos of snake feeding for my research. I also received help and support from many undergraduate students: Cassandra Fenner, Jessica Graham, Jennifer Miller, Brooke Patrick, Shahrzad “Sherry” Rahbar and Samuel Riggan. These students were not only enthusiastic and hardworking but were able to quickly see the benefit as well as the enjoyment that comes from carefully observing animals. Many others have provided wonderful support, encouragement and scintillating conversation throughout my education: David Cundall, Harry Greene, Javier Rodriguez-Robles and Randall Reiserer. My husband Jonathon Redwine, snake enthusiast at heart, was always ready to talk and listen about snake feeding biology. iv Equipment for this study was funded by the American Psychological Association (APA), the Department of Psychology at the University of Tennessee, Knoxville (UT), the U.T Scholarly Activities Research Incentive Fund (SARIF), and the Reptile Behavior Fund of the Burghardt Lab. Presentations of parts of this study to the Society of Integrative and Comparative Biology (SICB) and at the VII International Conference of Vertebrate Morphology (ICVM) were supported by the Department of Psychology at UT and the U.T Graduate Student Association. A sincere thank you is reserved for Dr. Jim Lawler, our Psychology Department head. On many occasions, Dr. Lawler helped me find a source of funding for needed laboratory equipment. I would like to thank my parents, Dr. Onkar and Dr. Sooi Mehta. Without their help, love, support and encouragement, I would be lost. I thank my brother Roy for his encouragement, ideas and editorial help. I am so grateful for my husband Jonathon for being a terrific sport in a long distance relationship. Jack has been a constant source of ideas, strength, encouragement and comic relief throughout my graduate career. I also must acknowledge my father, mother, and sister in-law: Dr. William and Shirley Redwine and Cynthia Redwine. I am extremely blessed to be married into such a wonderful and loving family. Last but not least, I thank my dog Marley for guarding the backyard when I had to work late and for always being happy to see me regardless of how late I came home. v ABSTRACT Among living tetrapod vertebrates, snakes exhibit the most radical shifts in feeding biology and among limbless squamate reptiles, only snakes have undergone a substantial adaptive radiation. The behavioral innovation, constriction, has been associated with the success of this clade. Constriction is a prey restraint behavior that enabled snakes to immobilize and subdue extremely large prey items relative to their own body mass. This behavior pattern is associated with the incredible shifts observed in snake feeding biology from consuming small meals frequently to less frequent feeding on large prey. Although constriction is an ethological homology for the majority of snakes, variations of constriction postures have been documented in many derived snake lineages. Nevertheless, the mechanisms driving behavioral variation are not well understood. In this dissertation, I attempt to use a comparative hierarchical approach to examine constriction behavior at both the ethological and physiological levels in order to better understand the behavioral variation of this key innovation. As reviewed in Part 1, derived snake lineages seem to have several methods with which to restrain prey. Prey restraint methods appear to vary with respect to prey characteristics (size, shape, activity level). On the other hand, intermediate taxa (boas and pythons) are thought to be less variable in the prey restraint phase of feeding. The kinematics of loop application pattern also appears to differ between intermediate and derived snake groups. Derived snakes use the lateral part of their body to wind prey whereas boas tend to bend ventrally around prey. The polarity for variable prey restraint behavior and
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