International Journal of Primatology

, Volume 19, Issue 6, pp 1061–1079 | Cite as

Changes in Orangutan Caloric Intake, Energy Balance, and Ketones in Response to Fluctuating Fruit Availability

  • Cheryl D. Knott


I used novel quantitative measures to assess the impact of fruit seasonality on changes in diet and energy balance during 4918 hours of observation on <60 orangutans in Gunung Palung National Park, West Kalimantan, Indonesia, from September 1994 through September 1995. During this period a mast fruiting occurred, resulting in large fluctuations in fruit availability, measured by monitoring of 558 orangutan fruit trees. Orangutan diet varied tremendously in accordance with these fluctuations. During the month of highest fruit production, 100% of the orangutan diet was composed of fruit. In contrast, during the fruit-poor period as little as 21% of the diet was fruit, while 37% was bark. Nutritional analyses of 78 of the foods most commonly eaten during this study show that mast foods were significantly higher in caloric content than were nonmast foods, which translates into substantial changes in caloric intake. During the month of highest fruit consumption (January), males consumed an estimated 8422 kcal/day and females consumed 7404 kcal/day. During the month of lowest fruit consumption (May), males consumed 3824 kcal/day and females consumed 1793 kcal/day. These differences were significantly different between the 2 months for both males and females. In May, males ate significantly more kcal/day than females did. Time spent feeding did not differ between the two periods for either males or females. I assessed the impact of these changes in diet and caloric intake on orangutan physiological functioning by measuring ketones in 257 urine samples collected from adult males and females. Ketones—products of fat metabolism—were present in urine only during the fruit-poor period. These data suggest that orangutans are highly efficient at storing fat during fruit-rich periods and utilizing the reserves during times of fruit shortfall. This response may have important implications for orangutan survivorship, reproduction, and behavior.

seasonality urine ketones energy balance ape 


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  1. American Dietetic Association (ADA) (1992). Manual of Clinical Dietetics, American Dietetic Association, Chicago.Google Scholar
  2. Appanah, S. (1981). Pollination in Malaysian primary forests. Malay. For. 44: 37–42.Google Scholar
  3. Altmann, J., Schoeller, D., Altmann, S. A., Muruthi, P., and Sapolsky, R. M. (1993). Body size and fatness of free-living baboons reflect food availability and activity levels. Am. J. Primatol. 30: 149–161.Google Scholar
  4. Ashton, P. S., Givinish, T. J., and Appanah, S. (1988). Staggered flowering in the Dipterocarpaceae: New insights into floral induction and the evolution of mast fruiting. Am. Nat. 132: 44–66.Google Scholar
  5. Association of Official Analystical Chemists (AOAC) (1984). Fat (crude) or ether extract in animal feeds: direct method. In Williams, S. (ed.), Official Methods of Analysis of the Association of Official Analytical Chemists, Association of Official Analytical Chemists, Arlington, VA, pp. 159–160.Google Scholar
  6. Curran, L. M., Leighton, M., and Nirarita, C. E. (1998). Temporal and spatial distribution of fruitfall in mast-fruiting Bornean Dipterocarpaceae 1986–96. I. Optimal germination, increased seed size and resource accumulation hypotheses. J. Ecol. (in review).Google Scholar
  7. Ellison, P. T., Panter-Brick, C., Lipson, S. F., and O'Rourke, M. T. (1993). The ecological context of human ovarian function. Hum. Reprod. 8: 2248–2258.Google Scholar
  8. Fischbach, F. A. (1988). Manual of Laboratory Diagnostic Tests, J. B. Lippincott, New York.Google Scholar
  9. Galdikas, B. (1988). Orangutan diet, range, and activity at Tanjung Puting, Central Borneo. Int. J. Primatol. 9: 1–35.Google Scholar
  10. Galdikas, B., and Wood, J. W., (1990). Birth spacing patterns in humans and apes. Am. J. Phys. Anthropol. 83: 185–191.Google Scholar
  11. Goering, H. K., and Van Soest, P. J. (1970). Forage fiber analysis. In Agricultural Handbook No. 379, ARS, USDA, Washington, DC.Google Scholar
  12. Goodall, J. (1986). The Chimpanzees of Gombe: Patterns of Behavior, Harvard University Press, Cambridge, MA.Google Scholar
  13. Knott, C. (1996). Monitoring health status of wild orangutans through field analysis of urine. Am. J. Phys. Anthropol. Suppl. 22: 139–140.Google Scholar
  14. Knott, C. (1997). Field collection and preservation of urine in orangutans and chimpanzees. Trop. Biodiv. 4: 95–102.Google Scholar
  15. Knott, C. D. (1998). Social system dynamics, ranging patterns and male and female strategies in wild Bornean orangutans (Pongo pgymaeus). Am. J. Phys. Anthropol. Suppl. 26: 140.Google Scholar
  16. Leighton, M. (1993). Modeling diet selectivity by Bornean orangutans: Evidence for integration of multiple criteria for fruit selection. Int. J. Primatol. 14: 257–313.Google Scholar
  17. Leighton, M., and Leighton, D. (1983). Vertebrate responses to fruiting seasonality within a Bornean rain forest. In Sutton, S. L., Whitmore, T. C., and Chadwick, A. C. (eds.), Tropical Rain Forest: Ecology and Management, Blackwell Scientific, Boston. pp. 181–196.Google Scholar
  18. MacKinnon, J. (1971). The orangutan in Sabah today. Oryx 11: 141–191.Google Scholar
  19. MacKinnon, J. R. (1974). The behaviour and ecology of wild orang-utans (Pongo pygmaeus). Anim. Behav. 22: 3–74.Google Scholar
  20. Medway, L. (1972). Phenology of a tropical rain forest in Malaya. Biol. J. Linn. Soc. 4: 117–146.Google Scholar
  21. Milton, K., and Demment, M. W. (1988). Digestion and passage kinetics of chimpanzees fed high and low fiber diets and comparison with human diet. J. Nutr. 118: 1082–1088.Google Scholar
  22. Mitani, J. C. (1989). Orangutan activity budgets: Monthly variations and effect of body size, parturition, and sociality. Am. J. Primatol. 18: 87–100.Google Scholar
  23. Mori, A. (1979). Analysis of population changes by measurement of body weight in the Koshima troop of Japanese monkeys. Primates 20: 371–397.Google Scholar
  24. National Academy of Science (NRC) (1980). Recommended Dietary Allowances, National Academy of Sciences, Washington, DC.Google Scholar
  25. Pierce, W. C., and Haenisch, E. L. (1947). Quantitative Analysis, John Wiley & Sons, London.Google Scholar
  26. Robertson, J. B., and van Soest, P. J. (1980). The detergent system of analysis and its application to humans foods. In James, W. P. T., and Theander, O. (eds.), The Analysis of Dietary Fiber in Food, Marcel Dekker, New York.Google Scholar
  27. Robinson, A. M. (1980). Physiological role of ketone bodies as substrates and signals in mammalian tissues. Physiol. Rev. 60: 143.Google Scholar
  28. Rodman, P. S. (1977). Feeding behavior of orangutans in the Kutai Reserve, East Kalimantan. In Clutton-Brock, T. H. (ed.), Primate Ecology, Academic Press, London, pp. 383–413.Google Scholar
  29. Rodman, P. S. (1979). Individual activity profiles and the solitary nature of orangutans. In Hamburg, D. L., and McDown, E. R. (eds.), The Great Apes, W. A. Benjamin, London, pp. 234–255.Google Scholar
  30. Rodman, P. S. (1984). Foraging and social systems of orangutans and chimpanzees. In Rodman, P. S., and Cant, J. G. H. (eds.), Adaptations for Foraging in Nonhuman Primates, Columbia University Press, New York, pp. 134–160.Google Scholar
  31. Sokal, R. R., and Rohlf, J. F. (1981). Biometry, W. H. Freeman, New York.Google Scholar
  32. van Schaik, C. P. (1986). Phenological changes in a Sumatran rainforest. J. Trop. Ecol. 2: 327–347.Google Scholar
  33. van Schaik, C. P., and Fox, E. A. (1996). Manufacture and use of tools in wild Sumatran orangutans. Naturwissenschaften 83: 186–188.Google Scholar
  34. van Schaik, C. P., and Van Noordwijk, M. A. (1985). Interannual variability in fruit abundance and the reproductive seasonality in Sumatran long-tailed macaques (Macaca fascicularis). J. Zool., Lond. A. 206: 533–549.Google Scholar
  35. Watson, J., and Jaffe, M. S. (1995). Nurse's Manual of Laboratory and Clinical Diagnostic Tests, F. A. Davis, Philadelphia.Google Scholar
  36. Wheatley, B. P. (1982). Energetics of foraging in Macaca fascicularis and Pongo pygmaeus and a selective advantage of large body size in the orang-utan. Primates 23: 348–363.Google Scholar
  37. Wheatley, B. P. (1987). The evolution of large body size in orangutans: A model for hominoid divergence. Am. J. Primatol. 13: 313.Google Scholar
  38. Whitmore, T. C. (1986). Tropical Rain Forests of the Far East, Oxford University Press, Oxford.Google Scholar

Copyright information

© Plenum Publishing Corporation 1998

Authors and Affiliations

  • Cheryl D. Knott
    • 1
  1. 1.Department of Anthropology, Peabody MuseumHarvard UniversityCambridge

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