Behavioral Change and Phenological Response in Captive Loggerhead Sea Turtles (Caretta Caretta): Seasonal Patterns and the Migra

Behavioral Change and Phenological Response in Captive Loggerhead Sea Turtles (Caretta Caretta): Seasonal Patterns and the Migra

BEHAVIORAL CHANGE AND PHENOLOGICAL RESPONSE IN CAPTIVE LOGGERHEAD SEA TURTLES (CARETTA CARETTA): SEASONAL PATTERNS AND THE MIGRATORY PROCESS A Thesis Presented to The Faculty of the College of Arts and Sciences Florida Gulf Coast University In Partial Fulfillment Of the Requirement for the Degree of Master of Science By Amber Shaw 2018 2 Florida Gulf Coast University Thesis APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirements for the degree of Master of Science Amber Shaw Approved: September 24th, 2018 Phil Allman, Advisor Win Everham, Committee Member Brian Bovard, Committee Member The final copy of this thesis has been examined by the signatories, and we find that both the content and the form meet acceptable presentation standards of scholarly work in the above mentioned discipline. 3 Acknowledgements The emotional cycle of completing a master’s thesis is the constant shift between feelings of excitement and achievement, followed by confusion and despair. The support and help provided by so many individuals throughout this process has been crucial to my success. Above all, I would like to thank the members of my thesis committee. I am grateful to Dr. Phil Allman, for agreeing to be my adviser. My situation was not typical of most graduate students, but he continually offered patience and guidance from a distance, and pushed me to work through the various challenges I faced. Dr. Win Everham and I spent many hours in the computer lab manipulating the environmental data. It was during these discussions that the idea of a “critical period” emerged as a way to elaborate phenological response. Dr. Brian Bovard’s assistance in the behavioral data analysis was invaluable every step (and misstep) of the way. I genuinely appreciate the time and effort all three of them made to coordinate committee meetings, exemplified by our first meeting in which they carpooled from Fort Myers to Sarasota to meet at my study site. I owe a huge thanks to my amazing coworkers, Holly West and Lauren Miller. Holly and I worked together for many years, and we had talked about investigating behavioral change in the captive loggerheads we cared for. Both she and Lauren, along with many wonderful interns, contributed to this study, conducting hundreds of observations and entering enormous amounts of data. They were both also willing to cover work shifts so I could return to school to pursue my graduate degree, and even more importantly, were sources of moral support throughout the entire process. Additionally, Dr. John Reynolds (although no longer with us), was a source of unwavering encouragement in my workplace. 4 I would also like to extend thanks to Mote Marine Laboratory and the Office of Research and Graduate Studies at Florida Gulf Coast University. Both institutions provided funding that helped support my pursuance of a graduate degree. Although my distance from FGCU prevented me from spending a lot of time with the Herpetology Research Lab, the group provided a sense of comradery for an exhausted graduate student, and it was motivating to see so much enthusiasm for reptiles and amphibians among the students. In particular, I want to thank Ivana Lezcano for taking an interest in my project and volunteering her time to go through some of the nocturnal video data for me. Finally, I want to thank my family. My love of animals and the natural world started at a very young age, and my parents have always supported my interests, even when it meant disappearing into the jungle for a few months in Costa Rica to tag nesting turtles. I could not have done any of this without the love and support of my husband, Carlie, and my daughter, Elia. They are my source of inspiration. I cannot express my gratitude to them enough for always being by my side and believing in me. <4. 5 This project would not have been possible without Montego and Shelley, the two best loggerheads I know. Thank you for being ambassadors for your species and helping educate the world about sea turtles. 6 Abstract Understanding vital life history processes is critical to the conservation and management of endangered species, especially in light of changing global climate conditions and the verging unknown impacts this will have on these mechanisms. The goal of this study was to employ direct observation methods on captive loggerhead sea turtles (Caretta caretta) to examine behavioral change as a proxy for the reproductive migratory process. Diurnal and nocturnal observations were conducted on two mature female loggerheads housed at Mote Marine Laboratory in Sarasota, Florida, from December 2013 through December 2015. Both turtles displayed a reduced interest in food during the winter season each year, which lasted approximately 11 weeks in 2014 and 14 weeks in 2015, with a five week difference in timing between individuals. This time period corresponded with observed change in activity levels, swim patterns, interactions, and location preferences for both animals. There was a rise in diurnal resting, coinciding with a decrease in diurnal swimming as well as a decrease in interactions with their environment. Activity levels increased at night, with some nights of prolonged heightened swimming episodes. One of the turtles exhibited a swim pattern of fixated, directional movement into the wall at increased frequency during this time frame. Both animals spent the majority of their time in a small section of their habitat proximal to the open sky. Three environmental variables (air temperature, photoperiod, and lunar phase) were tracked during this study to investigate potential zeitgebers in sea turtles. Patterns indicate a possible response to day length and stage of the moon, though these findings are speculative and require further research. Behavioral changes noted here suggest that reproductively mature sea turtles display a form of migratory restlessness in a captive setting, and turtles may utilize a nocturnal swimming strategy during the pre-nesting migration. This study highlights the importance of direct observations 7 when examining behavior and the benefits of using captive animals to help understand processes that are difficult to investigate in the wild. 8 Table of Contents Introduction …………………………………………………………………………………… 11 Goals and Objectives …………………………………………………………………………. 25 Methods ……………………………………………………………………………………….. 26 Study Species and Site ………………………………………………………………… 26 Experimental Design ………………………………………………………………….. 27 Data Collection ……………………………………………………………………….. 29 Statistical Analysis ……………………………………………………………………. 31 Results ………………………………………………………………………………………… 33 Diurnal Behavior ……………………………………………………………………... 34 Nocturnal Behavior …………………………………………………………………… 39 Environmental Factors ……………………………………………………………….. 40 Discussion …………………………………………………………………………………….. 47 Behavioral Change …………………………………………………………………… 49 Environmental Factors ……………………………………………………………….. 59 Future Studies ………………………………………………………………………… 65 Management Implications ……………………………………………………………. 67 Conclusions …………………………………………………………………………... 68 Literature Cited ………………………………………………………………………………. 70 Appendices ………………………………………………………………………………….... 79 9 List of Figures Figure 1. Conceptual diagram of a sea turtle’s life cycle ……………………………….......... 19 Figure 2. Images of study subjects (Turtle M and Turtle S) …………………………………. 26 Figure 3. Habitat and study site …………………………………………………………….... 30 Figure 4. Diurnal activity levels for Turtle M and Turtle S over a two year period …………. 35 Figure 5. Frequency of swim pattern for periods of decreased food interest and normal food interest for Turtle M and Turtle S ……………………………………………………………. 36 Figure 6. Interactions with rocks for Turtle M and EEDs for Turtle S ……………………… 38 Figure 7. Percentage of time Turtle M and Turtle S spent in each location within the habitat during the time frame of decreased food interest …………………………………………….. 40 Figure 8. Schematic of permanent habitat for study subjects ………………………………... 42 Figure 9. Nocturnal behavioral patterns for Turtle M and Turtle S …………………………. 43 Figure 10. Environmental factor trends beginning in the late fall and ending in the late winter for the 2013-14 season and 2014-15 season …………………………………………………. 44 Figure 11. Swim patterns exhibited by study subjects ………………………………………. 53 Figure 12. Turtle’s interactions with objects within the environment ………………………. 58 10 List of Tables Table 1. Description of behaviors listed in ethogram for diurnal and nocturnal observations… 28 Table 2. Summary of change in food interest for subjects from December 2013 through December 2015 ………………………………………………………………………………. 33 Table 3. SIMPER results showing the distance or dissimilarity between the proposed critical periods and the days outside of those periods, with respect to the environmental factors …... 41 Table 4. Environmental characteristics of the proposed critical periods for Turtle M and Turtle S ………………………………………………………………………………………. 45 11 Introduction Migration is a fascinating phenomenon; ubiquitous in the natural world and an integral part of the structure and function of many ecosystems (Fryxell et al. 2011, Shaw 2016). It can be defined a number of ways, but in general it is commonly agreed upon that a migration has one or more of the following attributes: focused, directed movement; movement over a long-distance and duration of time; and movement back and forth between distinct home ranges (Russell et al. 2005, Fryxell et al. 2011). Migratory behavior is seen in multiple life stages of a variety of taxa and occurs for

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