SOCIAL DOMINANCE: A BEHAVIORAL MECHANISM FOR RESOURCE ALLOCATION IN CRAYFISH Kandice Christine Fero A Dissertation Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY August 2008 Committee: Paul Moore, Advisor Verner Bingman Graduate Faculty Representative Sheryl Coombs Rex Lowe Steve Vessey ii ABSTRACT Paul Moore, Advisor Social dominance is often equated with priority of access to resources and higher relative fitness. But the consequences of dominance are not always readily advantageous for an individual and therefore, testing of such assumptions is needed in order to appropriately characterize mechanisms of resource competition in animal systems. This dissertation examined the ecological consequences of dominance in crayfish. Specifically, the following questions were addressed: is resource allocation determined by dominance and how does the structure of resources in an environment affect dominance relationships? By examining the mechanism of how dominance may allocate resources in groups of crayfish, we can begin to answer questions concerning what environmental selective pressures are shaping social behavior in this system. Shelter acquisition and use was examined in a combination of natural, semi-natural, and laboratory studies in order to observe dominance relationships under ecologically relevant conditions. The work presented here shows that: (1) social status has persisting behavioral consequences with regard to shelter use, which are modulated by social context; (2) dominance relationships influence the spatial distribution of crayfish in natural environments such that dominant individuals possess access to more space; (3) resource use strategies differ depending on social history and these strategies may influence larger scale segregation across habitats; and finally, (4) shelter distribution modulates the extent to which social history and shelter ownership influence the formation of subsequent dominance relationships. Taken together, these results demonstrate that dominance has significant consequences for crayfish resource acquisition and holding. However, a complex picture has been revealed as to the nature of dominance iii establishment and the potential resource benefits associated with dominance. Dominant crayfish posses control over shelter and space but the likelihood of becoming dominant and the subsequent resource use consequences are largely dependent on social and environmental context. iv For Dan, Young, Don, and Lee v ACKNOWLEDGMENTS I am grateful for this opportunity to express my deepest thanks and love for those who have supported me in this endeavor. I first must thank Dr. Paul Moore. Thank you Paul, for having so much passion and enthusiasm for the pursuit of knowledge and for always asking questions. Thank you for always being so generous with your time and energy. Thank you for your confidence in my abilities. Thanks to my dissertation committee, Dr. Vern Bingman, Dr. Sheryl Coombs, Dr. Rex Lowe, and Dr. Steve Vessey. Thank you for your suggestions, for stimulating conversations, and for your generous support and encouragement. Thanks to the Department of Biological Sciences and Bowling Green State University for four years of financial support and specifically, thank you Chris Hess, Linda Treeger, and Steve Queen for helping me countless times. Thank you Jay Skock, Nick Kolderman, Michael Braddock, and Jen Bergner for assistance with video analysis and Tom Zulandt, Art Martin, Jodie Simon and Jen Bergner for their assistance with field work. And thank you to the members of the Laboratory for Sensory Ecology for arguing with me, editing countless papers, collecting crayfish, helping me set up experiments and for being such dear friends. Thanks to the University of Michigan Biological Station for housing and research support. Funding for this research was provided by the following awards and fellowships to K.F.: the BGSU Katzner fund, Non-Service Fellowship and Outstanding Graduate Student Award, the Crustacean Society Graduate Research Fellowship and Best Student Paper Award (SICB 2006). Funding was also provided by a NSF grant to P.A.M. (IBN# 0131320). Now I must thank all of the wonderful people that helped me survive graduate school. Thank you Stephanie Coray and Katie Crane for your continuing friendship. Thank you Paula Furey for your friendship and camaraderie. I will never forget how we went through this process together, dragging each other to the finish line! Thank you Grounds for Thought for letting me vi spend hundreds of hours occupying your tables for the mere price of a couple of cups of coffee. Thank you to the Moore family for your kindness and always making me feel welcome. Thank you Rex and Sheryn Lowe for trusting me and Paula with your home. My time in Bowling Green has been enriched by your friendship and generosity. Thank you to the Chibucos family for welcoming me into your lives. Thank you to Marcus. Thank you for your immeasurable love and patience. Thank you for always reminding me of the joy and beauty in my life. Thank you for helping me trust myself. And finally, thank you my loving family. You’ve always accepted me for who I am and have trusted my decisions. You have given me an education but more importantly, you taught me how to think for myself, which is the reason I have chosen the path that I have. Your unconditional support and love make up the core of my self. I dedicate my accomplishment to you. vii TABLE OF CONTENTS Page CHAPTER I. GENERAL INTRODUCTION ...................................................................... 1 CHAPTER II. CONSEQUENCES OF SOCIAL DOMINANCE ON CRAYFISH RESOURCE USE ...................................................................................................... 6 Introduction .......................................................................................................... 6 Materials and Methods............................................................................................... 10 Results ............................................................................................................ 16 Discussion ............................................................................................................ 19 CHAPTER III. SOCIAL SPACING OF CRAYFISH IN NATURAL HABITATS: WHAT ROLE DOES DOMINANCE PLAY? .......................................................... 25 Introduction ............................................................................................................ 25 Materials and Methods............................................................................................... 28 Results ............................................................................................................ 33 Discussion ............................................................................................................ 34 CHAPTER IV. RESOURCE DISTRIBUTION AND SOCIAL STATUS INFLUENCE CRAYFISH HABITAT CHOICE ............................................................................. 38 Introduction ............................................................................................................ 38 Materials and Methods............................................................................................... 41 Results ............................................................................................................ 44 Discussion ............................................................................................................ 47 CHAPTER V. RESOURCE DISTRIBUTION EVENS THE PLAYING FIELD FOR SOCIAL DOMINANCE IN CRAYFISH.................................................................. 53 viii Introduction ............................................................................................................ 53 Materials and Methods............................................................................................... 55 Results ............................................................................................................ 60 Discussion ............................................................................................................ 63 CHAPTER VI. SUMMARY AND GENERAL CONCLUSIONS ...................................... 70 LITERATURE CITED .......................................................................................................... 77 APPENDIX A. FIGURE AND TABLES............................................................................. 89 ix LIST OF FIGURES Figure Page 1 Mean intensities of agonistic interactions for all-male populations .......................... 89 2 Dominance activity indices for three all-male populations ....................................... 90 3 Proportion of agonistic interactions that males engaged in and their final rank within the hierarchy................................................................................... 91 4 Mean number of hours that crayfish of differing ranks spent in shelter.................... 92 5 Mean percent of time that crayfish spent in shelter, out of shelter, and at the feeding area.......................................................................................................... 93 6 Mean shifts in dominance score of individuals in populations.................................. 94 7 Mean of the total shifts in dominance score for crayfish at three ranks .................... 95 8 Experimental arena with three different shelter