Studies of the physiological mechanisms underlying primate behavior are a major focus of current research. Considerable theoretical and empirical work has been devoted to investigating the hormonal bases and consequences of social behavior. This project will add to this body of knowledge through an integrated field and laboratory study of the behavioral endocrinology of male chimpanzees living in an unusually large community at Ngogo, Kibale National Park, Uganda. Behavioral observations of subjects will be collected during 12 months of fieldwork, while hormones will be assayed from urine collected non-invasively from them. These data will be combined to address several questions regarding the hormonal bases and consequences of two significant aspects of chimpanzee life, aggression and stress. Does reproductive aggression affect male chimpanzee testosterone levels? Does competition over estrous females and inter-community aggression elevate male testosterone? What factors affect secretion of the stress hormone, cortisol? Is cortisol mobilized in response to stressful events, such as territorial boundary patrols and hunting episodes? Do individual differences in personality influence male susceptibility to stress? Do coping mechanisms and social support reduce cortisol levels? The extraordinary size of the Ngogo chimpanzee community will provide large samples of males and an ideal opportunity to test hypotheses designed to address these questions.
This research will advance scientific knowledge in two important ways. First, results will improve our understanding of our closest living relatives by clarifying the hormonal mechanisms regulating their behavior. Second, findings from this research promise to shed light on the evolution of our own behavior. Humans and chimpanzees possess identical hormones and share several unique behaviors, such as lethal territorial aggression and social support provided by unrelated individuals. By determining whether similar physiological mechanisms underlie these behaviors, this research will provide insights into their evolution. Finally, an important consequence of this research will be to aid the conservation of chimpanzees, a highly endangered species. Field research activities will safeguard an area that supports an extremely high density of chimpanzees and one of the last remnants of tropical forest in East Africa.
