AGGRESSIVE CALLING IN TREEFROGS A Dissertation presented to the Faculty of the Graduate School At the University of Missouri In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy By MICHAEL STEWART REICHERT Dr. H. Carl Gerhardt, Dissertation Supervisor DECEMBER 2011 The undersigned, appointed by the dean of the Graduate School, have examined the dissertation entitled AGGRESSIVE CALLING IN TREEFROGS Presented by Michael Stewart Reichert A candidate for the degree of Doctor of Philosophy And hereby certify that, in their opinion, it is worthy of acceptance. H. Carl Gerhardt, Ph.D. Reginald Cocroft, Ph.D. Raymond Semlitsch, Ph.D. David Geary, Ph.D. ACKNOWLEDGEMENTS This work belongs to many people. I would first like to thank my family for always supporting my interests and doing everything they could to make sure I succeeded. Thanks to my Mom, Dad, Elizabeth, Rebecca, Will, Grandma and Grandpa Gerstle and Grandma and Grandpa Reichert. The highest acknowledgement must go to my wife, Flavia Barbosa, whom I met very early on in graduate school. She has been with me throughout the entire process and my work would be far inferior without her. We went through some very challenging times early in graduate school, and without each other’s support, I’m not sure we would have made it to where we are today. Flavia inspired me early on with her passion for science, and has had as much of an impact on my work as anyone. She’s been there with me in the field, running experiments, reading every draft I ever wrote and helping me keep a positive mental attitude. Not to mention that she is a delight to be around and has made my Ph.D. experience some of the best years of my life. I’m extremely fortunate to have her. Carl Gerhardt deserves nothing but the highest praise as an advisor. I can’t thank him enough first of all for taking me in, and then for setting an outstanding example as a scientist. He very carefully helped me get the ball rolling on my projects and has consistently provided insightful commentary when needed. I knew I’d be getting help from a great intellect when I signed up to come to MU, but I had no idea how fortunate I ii would be to be working with such a great naturalist as well. He taught me a lot while we were working in the field, and I’m grateful for that. I would also like to thank the other members of my committee: Rex Cocroft, Ray Semlitsch and Dave Geary. It has been a privilege to have such a collection of scientific talent to work with, and each of them has been very helpful in giving their own perspective on my studies. On the same note, I have been very lucky to have such talented labmates. I’m very grateful to them all for their comments on my work, help collecting frogs in the field, for enlightening me with their own interesting work, and just for being pleasant and professional to work with. So thanks to Noah Gordon, Jennifer Henderson, Sarah Humfeld, Katy Klymus, Carlos Martínez-Rivera, Mitch Tucker, and Jessica Wood. I started this work at the University of Texas and I am very grateful to Mike Singer for serving as my advisor while I was there. Although we didn’t have a lot in common in terms of research interests, I’m very appreciative that Mike was willing to give me a chance. I’d be in a very different place today if it weren’t for him. He also is by far the most entertaining person I have met in science, in addition to being an excellent researcher. For various assistance and advice on my research, thanks to Mark Bee, Ximena Bernal, John Christy, Richard Daniel, Zac Ernst, Michael Greenfield, Kit Murphy, Rachel Page, Mike Ryan and members of his lab, Johannes Schul, Josh Schwartz, Karen Warkentin and members of her lab, Allison Welch, Kent Wells, Mary Jane West- iii Eberhard, Lori Wollerman and Ping Yu. Several anonymous reviewers and journal editors also provided helpful comments on previous versions of those chapters in this dissertation that have been published. Thanks also to the support staff at the Smithsonian Tropical Research Institute in Panama and the Organization for Tropical Studies (especially Ronald Vargas) at La Selva, Costa Rica. The governments of Panama and Costa Rica as well as the Missouri Department of Conservation provided permission to carry out these studies. The support staff at the University of Missouri has been fantastic as well. Thanks to Shannon Dennis, Nila Emerich, Jan Gorman-McAdams, Josh Hartley, Steve Heinrich, Tyeece Little, Alan Marshall, Amy Miles, Barb Sonderman and Pat Willis. It has been a privilege to work with a lot of talented assistants and I’d like to especially thank them all. These people put in a whole lot of work on my project, and I would have never gotten nearly as much done without them. So thank you to Tanya Drew, Nick Fowler, Tim Golden, Daniel Gruhn, Carmen Harjoe, Kathryn Kettenbach, Will Li, and Benjamin Nickelson. Thanks also to other undergrads in the lab that I didn’t work with directly but that provided assistance collecting or caring for frogs: Brice Grunert, Erin Murray, Si Yol Yi and all the rest. I have been incredibly fortunate to receive financial support from the following organizations, whom I gratefully acknowledge in chronological order: the Carl Gottfried Hamilton Fellowship Fund, Smithsonian Institution 10 week predoctoral fellowship, Animal Behavior Society student research grant, a Graduate Assistance in Areas of iv National Need fellowship from the University of Missouri and the US Department of Education, research grant from the Chicago Herpetological Society, travel grant from the US National Science Foundation and the Animal Behavior Society, Gaige Fund Award from the American Society for Ichthyologists and Herpetologists, Research Fellowship from the Organization for Tropical Studies (the Lillian and Murray Slatkin Fellowship and the Christiane and Christopher Tyson Fellowship), a Doctoral Dissertation Improvement Grant (IOS–1010791) from the US National Science Foundation, and a Dean Metter Award from the Society for the Study of Amphibians and Reptiles. v TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................................ii LIST OF TABLES .................................................................................................................... ix LIST OF FIGURES .................................................................................................................. xi ABSTRACT .......................................................................................................................... xiii CHAPTER 1. General introduction ...................................................................................... 1 CHAPTER 2. Aggressive thresholds in Dendropsophus ebraccatus: Habituation and sensitization to different call types Abstract ................................................................................................................. 13 Introduction .......................................................................................................... 14 Methods ................................................................................................................ 19 Results ................................................................................................................... 27 Discussion.............................................................................................................. 29 CHAPTER 3. Effects of multiple-speaker playbacks on aggressive calling behavior in the treefrog Dendropsophus ebraccatus Abstract ................................................................................................................. 43 Introduction .......................................................................................................... 44 Methods ................................................................................................................ 47 Results ................................................................................................................... 56 Discussion.............................................................................................................. 62 vi CHAPTER 4. Call timing is determined by response call type, but not by stimulus properties, in the treefrog Dendropsophus ebraccatus Abstract ................................................................................................................. 80 Introduction .......................................................................................................... 81 Methods ................................................................................................................ 85 Results ................................................................................................................... 96 Discussion............................................................................................................ 101 CHAPTER 5. Aggressive calls improve leading callers' attractiveness in the treefrog Dendropsophus ebraccatus Abstract ............................................................................................................... 113 Introduction ........................................................................................................ 114 Methods .............................................................................................................. 119 Results ................................................................................................................