Doctoral Dissertation Improvement: C-peptide of Insulin as an Index of Energy Expenditure in Wild Chimpanzees

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Chimpanzees will be observed in Kibale National Park, Uganda, to test the hypothesis that daily variation in urinary C-peptide (UCP) levels among adult males is correlated with both food intake and energetically expensive behaviors, such as aggression. The C-peptide molecule is a by-product of insulin synthesis and when excreted in the urine gives an accurate indication of insulin production. Insulin stimulates the uptake of glucose from the bloodstream and thus reflects the availability of energy for the organism.This study will provide the first direct assessment of the effectiveness of C-peptide, as an index of energy balance in wild primates. Previous assessments have been indirect since they used monthly averages of dietary quality, rather than daily monitoring of individual behavior. This research is designed to explain why dominant male chimpanzees have been reported to have lower UCP levels than subordinates, even though UCP levels track energy intake, being higher when and where fruit availability is greater.The intellectual merit of this study lies in the possible implications its findings will have for the methodological development of energetics research in field conditions. Non-invasive indices of the energetic condition of primates have always been elusive. C-peptide is promising as an indicator of energetic balance, energy intake, or energy expenditure and this study will assess its value. Understanding the relationship between energy expenditure in male chimpanzees and their dominance rank will also reveal hitherto overlooked energetic costs of dominance in social mammals.The broader impacts of the project include the contribution to the functioning of Makerere University Biological Field Station. Educational programs will be carried out in local schools to raise awareness and interest in wildlife. This doctoral dissertation research project will contribute to the academic training of a graduate student and the results will be published in peer-reviewed journals.