Stress, Energetics and the Costs of Reproduction in Wild Chimpanzees

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Stress, Energetics and the Costs of Reproduction in Wild ChimpanzeesObtaining accurate, regular assessments of energetic condition is a major challenge in studies of wild mammals. For behavioral ecologists, it is particularly important to record non-invasive measures of condition that impact neither behavior nor energy budgets. Preliminary research indicates that urinary C-peptide, a byproduct of insulin production, is a reliable and sensitive indicator of energy balance in apes. This study will employ non-invasive urine sampling to understand variation in energetic condition in wild chimpanzees (Pan troglodytes schweinfurthii). Measurements of both C-peptide and cortisol (a stress hormone) will be used to quantify the independent effects of energetic and social stress on chimpanzee growth, reproduction and health.The research exploits a unique 14-year dataset of urine samples and behavioral and ecological data from the Kanyawara chimpanzees in Kibale National Park, Uganda. Together with new, targeted observations, these data will test hypotheses about social dominance and the costs of reproduction. For females, the study will examine such costs over the reproductive cycle, with attention to differences between females living in rich and poor habitats. For male chimpanzees, the study will examine the impact of mating competition on energy budgets and health. The study tests the hypothesis that competition results in increased stress for dominant animals, reflecting the substantial energy costs of male reproduction. Results will shed light on the potential constraints on acquisition and maintenance of high status in this and other species. The broader impacts of this study will contribute to understanding the causes and consequences of energetic and social stress thus furthering conservation goals, particularly when ape populations visited by tourist groups can be regularly monitored. The project will support Ugandan field assistants, a post-doc, and at least one US graduate student. As a long-term research presence, the Kibale Chimpanzee Project will continue to support broader activities in chimpanzee conservation and community development.