1Department of Anthropology, Boston University, 2Department of Anthropology, University of New Mexico
Friday 4:00-4:15, Galleria North
In energy-limited environments, life history theory posits a trade-off between reproduction and maintenance of physiological condition. However, obtaining a measurement of this trade-off is challenging. C-peptide, a product of the conversion of pro-insulin to insulin, has been shown to be a reliable indicator of energetic condition in wild apes. Here we use this tool to test hypotheses about the relative cost of reproduction in both male and female wild Bornean orangutans. Results come from over 2000 samples collected at Gunung Palung National Park, in West Kalimantan, Indonesia from 1994 through 2011. In females, we found highest C-peptide values in non-lactating, non-pregnant females, supporting our prediction that freed from the cost of reproduction females are able to maintain highly positive energetic status. Significantly lower C-peptide values were found in lactating females, supporting the prediction that this is the most energetically draining stage for females. This contributes to our understanding of why orangutans have such long inter-birth intervals as they may take many years to regain positive energetic status. Interestingly, pregnant females were able to maintain relatively high C-peptide levels. This may reflect a similar mechanism as found in humans, where women are able to add fat reserves during pregnancy to support the cost of lactation. In males we found that prime, flanged male orangutans exhibited the highest C-peptide levels, reflective of their good condition. In contrast, flanged past prime males, exhibiting deteriorated physical condition, had the lowest C-peptide values recorded. Unflanged males were able to maintain relatively neutral levels.
Principle supporters: National Science Foundation; National Geographic Society; Leakey Foundation; US Fish and Wildlife; Orangutan Conservancy; Conservation, Food and Health Foundation.