International Journal of Primatology

, Volume 27, Issue 6, pp 1535-1550

First online:

Dietary and Energetic Responses of Pongo abelii to Fruit Availability Fluctuations

  • S. A. WichAffiliated withBehaviroural Biology Department, Utrecht, UniversityGreat Ape Trust of Iowa Email author 
  • , S. S. Utami-AtmokoAffiliated withUniversitas Nasional
  • , T. Mitra SetiaAffiliated withUniversitas Nasional
  • , S. DjoyosudharmoAffiliated withTaman Nasional Gunung Leuser
  • , M. L. GeurtsAffiliated withBehaviroural Biology Department, Utrecht, UniversityGreat Ape Trust of Iowa

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Like many primates, orangutans face fluctuations in fruit availability. We show that in Ketambe (Sumatra), fruit availability fluctuations have very little influence on orangutan diet. Most importantly, the percentages of fruits including figs, fruits excluding figs, and figs in their diet do not differ significantly between periods of varying fruit availability. In addition, there is no trace of ketones in orangutan urine samples during periods of varying fruit availability. Unlike 1 orangutan population in Borneo, orangutans in Sumatra experience no prolonged negative energy budget because of fluctuations in fruit availability. Dietary data from other Sumatran and Bornean orangutan populations indicate that the pattern might be representative for a more general difference between Sumatra and Borneo, and we discuss how this might have affected orangutan reproduction and life history for the 2 species.


diet ketones orangutan phenology