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Orangutan Energetics and the Influence of Fruit Availability in the Nonmasting Peat-swamp Forest of Sabangau, Indonesian Borneo

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Abstract

Data on energy intake and the effects of fluctuations in fruit availability on energy intake for African apes, and orangutans in mast-fruiting habitats, indicate that orangutans may face greater energetic challenges than do their African counterparts. Comparable data on orangutans in nonmasting forests, which experience lower fluctuations in fruit availability, have been lacking, however, complicating interpretations. We conducted a 46-mo study of orangutan energetics in the nonmasting Sabangau peat-swamp forest, Indonesian Borneo. Sabangau orangutans experienced periods of negative energy balance apparently even longer than in mast-fruiting habitats, as indicated by comparisons of observed energy intake with theoretical requirements and analysis of urinary ketones. Daily energy intake was positively related to fruit availability in flanged males, but not in adult females or unflanged males. This may represent different foraging strategies between age-sex classes and suggests that fruit availability is not always an accurate indicator of ape energy intake/balance. Urinary ketone levels were not generally related to fruit availability, daily energy intake, day range, or party size. This is probably due to low energy intake, and consequently high ketone production, throughout much of the study period. Comparisons with published results on African apes support the hypothesis that orangutans are unique among hominoids in regularly experiencing prolonged periods of negative energy balance. This has important effects on orangutan behavior and socioecology, and has likely been a key factor driving the evolutionary divergence of orangutans and African apes.

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Acknowledgments

We thank the Indonesian Institute of Sciences (LIPI), Director General of Nature Conservation (PHKA), and Centre for the International Cooperation in Management of Tropical Peatlands (CIMTROP) for research permissions. Funding was provided by the Leakey Foundation, Wildlife Conservation Society, U.S. Fish and Wildlife Service, Wingate Foundation, Primate Conservation Inc., Conservation International Primate Action Fund, IdeaWild, Cambridge Philosophical Society, Columbus Zoo, the Rufford Foundation, and the Orangutan Tropical Peatland Project (OuTrop). Simon Husson, Susan Cheyne, and Suwido Limin provided support and assistance throughout. We thank Cheryl Knott, Susan Cheyne, Nancy Conklin-Brittain, Kevin Potts, Ben Buckley, and Kirsten Manduell for information and comments that helped improve the manuscript. We especially thank the numerous field assistants and students who helped with data collection, and W. Rosa Farida and Tri Hadi Handayani for performing nutritional analyses. The editor and 2 anonymous reviewers provided comments that improved the manuscript. This paper is dedicated in loving memory of Jery Yenyahu Akar (“Zeri”): fantastic assistant, true anak rimba, and friend.

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  1. Wildlife Research Group, The Anatomy School, University of Cambridge, Downing Street, Cambridge, CB2 3DY, UK

    Mark E. Harrison, Helen C. Morrogh-Bernard & David J. Chivers

  2. Orangutan Tropical Peatland Project, Centre for the International Cooperation in Management of Tropical Peatlands, University of Palangka Raya, Palangka Raya, Central Kalimantan, Indonesia

    Mark E. Harrison & Helen C. Morrogh-Bernard

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Harrison, M.E., Morrogh-Bernard, H.C. & Chivers, D.J. Orangutan Energetics and the Influence of Fruit Availability in the Nonmasting Peat-swamp Forest of Sabangau, Indonesian Borneo. Int J Primatol 31, 585–607 (2010). https://doi.org/10.1007/s10764-010-9415-5

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