Distribution and conservation status of the orang-utan (Pongo spp.) on Borneo and Sumatra: How many remain?

Serge A. Wich, Erik Meijaard, Andrew J. Marshall, Simon Husson, Marc Ancrenaz, Robert C. Lacy, Carel P. Van Schaik, Jito Sugardjito, Togu Simorangkir, Kathy Traylor-Holzer, Matt Doughty, Jatna Supriatna, Rona Dennis, Melvin Gumal, Cheryl D. Knott, Ian Singleton

Research output: Contribution to journalReview articlepeer-review

154 Citations (Scopus)


In recognition of the fact that orang-utans (Pongo spp.) are severely threatened, a meeting of orang-utan experts and conservationists, representatives of national and regional governmental and non-governmental organizations, and other stakeholders, was convened in Jakarta, Indonesia, in January 2004. Prior to this meeting we surveyed all large areas for which orang-utan population status was unknown. Compilation of all survey data produced a comprehensive picture of orang-utan distribution on both Borneo and Sumatra. These results indicate that in 2004 there were c. 6,500 P. abelii remaining on Sumatra and at least 54,000 P. pygmaeus on Borneo. Extrapolating to 2008 on the basis of forest loss on both islands suggests the estimate for Borneo could be 10% too high but that for Sumatra is probably still relatively accurate because forest loss in orang-utan habitat has been low during the conflict in Aceh, where most P. abelii occur. When those population sizes are compared to known historical sizes it is clear that the Sumatran orang-utan is in rapid decline, and unless extraordinary efforts are made soon, it could become the first great ape species to go extinct. In contrast, our results indicate there are more and larger populations of Bornean orang-utans than previously known. Although these revised estimates for Borneo are encouraging, forest loss and associated loss of orang-utans are occurring at an alarming rate, and suggest that recent reductions of Bornean orang-utan populations have been far more severe than previously supposed. Nevertheless, although orang-utans on both islands are under threat, we highlight some reasons for cautious optimism for their long-term conservation.

Original languageEnglish
Pages (from-to)329-339
Number of pages11
Issue number3
Publication statusPublished - Jul 2008


  • Borneo
  • Decline
  • Great ape
  • Orang-utan
  • Pongo
  • Sumatra


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