International Journal of Primatology

, Volume 31, Issue 4, pp 647–663 | Cite as

Adaptation to Forest Life During the Reintroduction Process of Immature Pongo abelii

  • Barbara Riedler
  • Eva Millesi
  • Peter H. Pratje


Reintroduction of Sumatran orangutans can be an important tool to conserve the species in the face of the current decline of wild populations. Monitoring ex-captive orangutans during the reintroduction process provides insight into their adaptation to forest life and is important for evaluating the success of such programs. We investigated activity patterns, food choice, height use, and nest-building abilities of 8 immature orangutans at a reintroduction station in Sumatra. All focal individuals spent most of their time in the forest feeding, but at a lower proportion than wild conspecifics. Among the focal individuals, the behavior of orangutans that avoided human contact differed in several aspects from those that were human bonded. Their diet was composed mainly of fruits, similar to the food choice of wild orangutans, and their ground-avoidance and superior nest-building abilities indicated more effective predation-avoidance behavior vs. that of human-bonded animals. Finally, these immatures showed regular social contact with more experienced conspecifics, which ultimately may facilitate the social learning of local feral expertise. Human-bonded individuals, in contrast, preferentially stayed on the ground and at low heights and rarely built nests, thereby increasing predation risk. Their choice of leaves over fruits as foods indicated a less effective foraging strategy. Nevertheless, this group exhibited individual learning trends toward an adult-like foraging pattern and height use. We conclude that social interactions with conspecifics and humans, especially during an early developmental period, can affect adaptation to forest life and probably also influence the success of orangutan reintroduction processes.


foraging height use immature orangutan reintroduction 



We thank the Indonesian Institute of Science (LIPI) for permission to work in Indonesia, and the Directorate General of Forest Protection and Nature Conservation and the Nature Conservation Departments of the Provinces of Riau and Jambi for permission to conduct research at Bukit Tigapuluh National Park. We thank the University of Vienna for providing financial support for this study and the Frankfurt Zoological Society for logistic as well as financial support. We thank Isa, Damson, Suparman, Arlen, Habib, Josua, Krismanko, Marjuni, Sumarno, Puji, Syarif, and all local guides for their help in the field, and Betty for administrational advice. Finally, we thank 2 anonymous reviewers for many helpful comments on an earlier version of this manuscript.


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Barbara Riedler
    • 1
  • Eva Millesi
    • 1
  • Peter H. Pratje
    • 2
  1. 1.Department of Behavioural BiologyUniversity of ViennaViennaAustria
  2. 2.Indonesia Programme, Frankfurt Zoological SocietySumatraIndonesia

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