Abstract # 5883 Event # 118:

Scheduled for Sunday, September 14, 2014 03:15 PM-03:30 PM: Session 19 (Decatur A) Oral Presentation


FACTORS INFLUENCING REVISITATION RATES TO FEEDING TREES IN WILD BORNEAN ORANGUTANS (PONGO PYGMAEUS WURMBII) IN CENTRAL KALIMANTAN, INDONESIA

K. E. Markham1,4, M. A. van Noordwijk2 and E. R. Vogel3
1University of Victoria, Department of Anthropology, Victoria, BC V8P 5C2, USA, 2Anthropological Institute and Museum, University of Zurich, Zurich, Switzerland, 3Department of Anthropology, Center for Human Evolutionary Studies, Rutgers, The State University of New Jersey, New Brunswick, NJ, 08901, USA, 4Department of Anthropology, Boston University
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     The Bornean rainforests are often viewed as impoverished habitats for vertebrate frugivores, including orangutans. These forests are characterized by unpredictable and overall low fruit availability. Thus, it is likely that orangutans have evolved behavioral mechanisms to maximize energy intake while reducing foraging effort. Revisting feeding trees is one such mechanism. We hypothesized that orangutans would be more likely to visit the most productive trees and those trees that have the highest energetic return. Data from 2005-2010 on wild Bornean orangutans collected in the Tuanan Research Project area were analyzed to determine the frequency at which orangutans (n=35) revisited feeding trees. We used Vanderploeg and Scavia’s Index of Selectivity as a proxy for preference and used generalized linear mixed effects models and model averaging to determine the best fit model. Orangutans rarely revisited trees after three months from the initial visit, likely because fruit was no longer available. Preliminary results show a positive relationship between both diameter-at-breast height (DBH) and preference with the number of visitations (z=2.668, p=0.008, z=2.534, p=0.011, respectively), but that monthly fruit availability is also included in the best-fitting model, despite not reaching statistical significance (z=-1.392, p=0.164). Preference is also positively correlated with energy intake per patch (p<0.0001). Thus, the largest trees with the highest preference scores are revisited most often, indicating individuals revisit the trees with the greatest reward.