Abstract # 6027 Event # 193:

Scheduled for Monday, September 15, 2014 11:45 AM-12:00 PM: Session 25 (Mary Gay) Oral Presentation


NUTRITIONAL BALANCING IN WILD BORNEAN ORANGUTANS: THE INFLUENCE OF SEASONALITY

E. R. Vogel1,2,3, T. D. Bransford1, M. A. van Noordwijk4, D. Raubenheimer5 and J. M. Rothman6
1Rutgers University, Department of Anthropology, 131 George Street RAB 307, New Brunswick, NJ 08901, USA, 2Center for Human Evolutionary Studies, Rutgers University, 3Department of Ecology and Evolution, Rutgers University, 4Anthropologisches Institut und Museum, Universität Zürich, 5Charles Perkins Centre and School of Biological Sciences and Faculty of Veterinary Sciences, University of Sydney, 6Department of Anthropology, Hunter College
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     The rainforests of Borneo are considered impoverished habitats for vertebrate frugivores, such as orangutans. The peatland forests of Borneo have high densities of orangutans and are characterized by overall low and unpredictable fruit production. Previous work at the Tuanan Orangutan Research Station (TORP) area in Central Kalimantan, a peatland forest, has demonstrated that while the orangutans prefer fruit, they fallback on low energy foods during episodes of fruit scarcity. However, we have little understanding of how they balance and prioritize nutrients and how this is affected by fruit availability. We examine variation in nutrient intake across age-sex classes over a 7-year period. We hypothesized that orangutans would more tightly maintain their target intake of protein (P) than non-protein energy (nPe) when ecologically constrained to eat a diet that is imbalanced with respect to macronutrients (“protein prioritization”). We conducted 2,233 full-day nest-to-nest focal follows on 49 habituated orangutans (Pongo pygmaeus wurmbii) totaling over 39,000 hours of observations. Diet varied in macronutrient balance across different fruiting periods, showing a negative relationship between fruit availability and the P:nPe ratio (p<0.05). As predicted from previous studies on frugivores, protein intake was maintained more tightly than non-protein intake, a pattern that is consistent with protein prioritization. Daily caloric intake was lower during episodes of fruit scarcity across all age-sex classes (p<0.0001), indicating that the availability of fruit constrains energy intake.