Anthropology, Yale University
Thursday 3:30-3:45, Galleria South
Recent studies of non-human primates have demonstrated urinary C-peptide is a valuable biomarker of energetic condition. C-peptide tracks seasonal variation in food availability and is sensitive enough for intra- and inter-individual comparisons. Validation of C-peptide allows quantification of the costs of dominance, reproductive effort, reproductive state, and immune challenges in a way that was not previously possible. In this study, we applied this method to 40 adult and adolescent male chimpanzees at Ngogo,Kibale National Park,Uganda. This site is of special interest because Ngogo chimpanzees, compared to their neighbors at Kanyawara, enjoy higher daily and monthly net caloric gains. This is most likely due to occupying a habitat that is less variable in fruit production and more abundant in high quality food sources. We analyzed 420 samples for urinary C-peptide with corresponding phenology data, and over 1,000 hours of behavioral data. Food availability varied seasonally during this two year study period. However, contrary to predictions and in contrast to findings at Kanyawara, average C-peptide levels did not vary significantly by food availability. These results suggest that Ngogo male behavioral modifications are sufficient to avoid reductions in energetic condition during periods of lower food availability. Other primates reduce energy expenditure by reducing travel time or increasing resting time in these contexts, but this does not seem to be the case at Ngogo. Instead, we suggest that males cope by decreasing party size during relatively lean times. This research highlights the importance of exploring habitat variation in behavioral ecology.
This study was funded by the L.S.B. Leakey Foundation, the International Primatological Society, the American Society of Primatologists, Explorers Club, and the Yale Center for Human and Primate Reproductive Ecology.