Behavioral Ecology of Singing in the Heart-Nosed Bat
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BEHAVIORAL ECOLOGY OF SINGING IN THE HEART-NOSED BAT, CARDIODERMA COR A Dissertation by GRACE CHRISTINA SMARSH Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Michael Smotherman Committee Members, Adam Jones Gil Rosenthal Sharon Gursky Head of Department, Tom McKnight August 2017 Major Subject: Biology Copyright 2017 Grace Smarsh ABSTRACT Although singing has been recently recognized in some bat species, the prevalence and ecological significance of this behavior in bats is still mysterious. Cardioderma cor, the heart-nosed bat, was one of the first bats reported to sing, but little is known about the behavior of this species. Unlike other singing bats, this species roosts in groups during the day but disperses nightly to exclusive foraging areas, whereupon they sing from perches. The goal of this dissertation was to investigate the behavioral ecology of singing in C. cor, addressing key questions such as which bats sing, when and where they sing, and what and why they sing. I conducted a series of experiments to test the hypothesis that C. cor sings to create and defend foraging territories, a behavior commonly observed in songbirds but not mammals. I recorded the singing and sonar behavior of individuals across three field seasons in Tanzania. I mist-netted, tagged, and VHF-tracked 14 individuals to collect movement and singing data. Finally, I conducted acoustic playback experiments with 10 singers. C. cor males showed high fidelity to closely abutting night ranges that varied in size from 0.97 to 5.23 ha. Males foraged early in the evening before singing from preferred perches for up to several hours. I documented two C. cor song types, the most frequent being a “loud” song and less frequently a “soft” song uttered at the height of the dry season. Songs varied within individuals, but each individual’s songs were distinguishable by a unique set of spectral and temporal syllable parameters. C. cor and the sympatric, confamilial yellow-winged bat, Lavia frons, had overlapping foraging territories. However, C. cor’s repertoire was distinctive from that of L. frons’. Song playback experiments with C. cor elicited strong movement responses and changes in singing. Results suggested that song spectral and temporal parameters influenced behavioral responses. The results of this dissertation support the conclusion that C. cor’s singing behavior is consistent with the territory defense hypothesis for the evolution of singing, and suggest that song variability is likely integral to social interactions by facilitating individual discrimination or signaling motivational states. ii DEDICATION To the villagers of Kikavuchini, Mkalama, and Longoi, for their friendship, support, and noisy bats. iii ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Smotherman, and my committee members, Dr. Jones, Dr. Gursky, and Dr. Rosenthal for their guidance and support throughout the course of this research. Their critical reviews of my progress before and after each field season was crucial for the improvement and success of these field data. Special thanks goes to my advisor, Dr. Smotherman, for his continual support both in the US and in TZ, who gave me free reign to pursue this project, enthusiastically embraced the study of bat singing behavior, reviewed my many grant proposals and manuscript drafts, took the countless hours to continually discuss my research progress, took phone calls from me at odd times while in the bush to discuss methodological and logistical issues, and even went to TZ during my first field season to hand-deliver tracking equipment and discuss research progress. I would like to thank the individuals who were integral to the creation of this project. Dr. Kim Howell of the University of Dar es Salaam, Dr. Bruce Patterson at the Chicago Field Museum and his colleague, Anna Goldman, and Dr. Merlin Tuttle of Bat Conservation International answered my many questions and gave advice on acquiring for and applying for research permits to work in Tanzania, as well as locating and studying the African megadermatid bat species. Thank you to Dr. Kim Howell in particular for reviewing my permit applications and progress reports every year. Dr. Victor Kakengi at the Tanzania Wildlife Research Institute was patient in answering my questions and concerns about acquiring approval to work in different regions in Tanzania. Dassa Nkini at the Tanzania Conservation Research Centre worked hard to help me acquire my residency permits and research permits in a timely manner, and thus I greatly appreciate her efforts. Thanks goes to Peter Jones of the Ndarakwai Conservation Area for allowing me to conduct research on his property, and also generously providing me assistance for this project, such as a campsite, water, and electricity access, and allowing me to hire some of his askaris (guards) for our protection while conducting our night work in the area on iv foot. Thanks to Cha Cha and Everesti for their askari work, amidst hyenas, leopards, lions, and buffalo in the area. I thank Ailsa Dixon, the camp manager, for her friendship and support in this location. I thank the Village Officers of Kikavuchini, Mkalama, and Longoi, as well as Miti Mirefu, for their cooperation and assistance in helping conduct research in the area. In particular, I thank Mercy, the VO of Kikavuchini in 2012, for helping me find a suitable residence for my team, and her enthusiasm and kindness for our work from the very start. I thank the Macheme Weru Weru Ward Officers, the Sihai and Hai District Officers, and the Moshi Regional Director for their cooperation and permissions to work in these areas. I thank Jumanne Masonda, the Managing Director at Sable Wildlife Training Centre LTD, for connecting me with recent graduates to hire and train in research for this project. Special thanks go to the field assistants who worked very hard throughout the night to track, record, and conduct experiments on these bats, in the heat at the end of the dry season and in the wet weather of the rainy seasons: Felix Mpelembwa, Nuhu Bahaty Mhapa, Alfred Absolem Mollel, Nickodemasy Obeid, and Rogers Eliau. Their continual enthusiasm and energy for wildlife work was important for the success of this project. I also thank my good friend, Mama Mustafa, who cooked delicious meals for us so we had the energy to carry on this work, helped maintain our residence, and helped me practice and improve upon KiSwahili over many a conservation in solely KiSwahili. Thanks goes to my friend Elisiana Leonard who also pitched in during her break between college semesters, and added some fun to the group. I thank the advice on statistics and experimental design from Dr. Mirjam Knӧrnschild, Dr. Thomas DeWitt, Brian Pierce, Dr. David L. Jones, and finally, Dr. Kirsten Bohn, who initially piqued my interested in singing bats and caused me to apply to Texas A&M University. I thank Dr. Ryan Sinnet for our MATLAB discussions and assistance with code. I thank my colleague Tim Divoll and Dr. Ashley Long for their advice on home range analysis methods. Dr. Jill Heatley in the College of Veterinary Medicine at Texas A&M University trained me in methods to safely and ethically apply PIT tags to bats. I would also like to thank our administrative staff William Bailey and v Jennifer Bradford for their assistance in handling my complicated financial issues, particularly while I was abroad. I would like to thank my colleagues from the Smotherman Lab, and early on, the Lints Lab, for their discourse on this project, help in reviewing grant proposals, and overall friendship and enthusiasm. From the Smotherman Lab, I thank Dr. Jenna Jarvis, Samantha Trent, Alyson Brokaw, Dr. Amanda Adams, and undergraduates Kelly Rogers, Kaylee Davis, and Marie Kasbaum. From the Lints Lab, I thank Kimberly Page, and Dr. Mugdha Deshpande, who brought me into the world of songbirds and their singing behavior. I especially thank my friends and family for their encouragement during the long process of establishing and conducting this work, both at home and abroad. My sister, Dr. Danielle Smarsh, my parents, and my grandfather lent their ears during many a stressful moment. Various village and traveling friends were supportive during the busy field seasons, especially Bibi Tatu and Teacher Mary Kiravu of Kikavuchini, and Emily Okallu, John St. Julien, Ailsa Bennell, Ngozi Iroanyah, and Sarah Ellis who were pursuing various projects and research. Stateside, my various friends were very encouraging throughout the years. I thank Dr. Ryan Sinnet for his continual encouragement, support, and good humor throughout this process. vi CONTRIBUTORS AND FUNDING SOURCES Contributors This work was supervised by a dissertation committee consisting of Professor Michael Smotherman (chair), Professor Adam Jones, and Professor Gil Rosenthal of the Biology Department, as well as Professor Sharon Gursky of the Anthropology Department. Planning, executing and analyzing the work completed for this dissertation was largely carried out by the author. Dr. Smotherman contributed by discussing experimental plans and results, and editing many writing samples. Dr. Thomas DeWitt and Brian Pierce assisted with discourse and review of multivariate data methods, particularly in Ch. 4. Dr. Ryan Sinnet reviewed code written for Ch. 2. Dr. David Jones reviewed and modified code for multivariate statistics used in Ch. 4. Dr. Mirjam Knӧrnschild discussed multivariate methods of analyzing acoustic data, used in Ch. 2 and 3. Dr. Ashley Long provided advice on subsampling and bandwidth selection methods for Ch. 5. Funding Sources Graduate study was partially funded by the NSF Graduate Research Fellowship Program (3-year stipend). Equipment and travel was covered by two Student Scholarship grants from Bat Conservation International and additional funding from Wildlife Acoustics.