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The status of the Sumatran orang-utan Pongo abelii: an update


S. A. Wich a1c1, I. Singleton a2, S. S. Utami-Atmoko a3, M. L. Geurts a1, H. D. Rijksen a4 and C. P. van Schaik a5
a1 Sumatran Orang-utan Conservation Programme, P.O. Box 1472, Medan 20001, Sumatera Utara, Indonesia
a2 Universitas Nasional, Jl. Sawo Manila, Ps. Minngu, Jakarta, Indonesia, and Utrecht University, Behavioural Biology, P.O. Box 80086, 3508 TB, Utrecht, The Netherlands
a3 Utrecht University, Behavioural Biology, P.O. Box 80086, 3508 TB, Utrecht, The Netherlands
a4 Federation for International Nature Protection, Sparrenbos 19, 6705 BB Wageningen, The Netherlands
a5 Biological Anthropology and Anatomy, Duke University, Box 90383, Durham, NC 27708-0383, USA

Abstract

The Sumatran orang-utan Pongo abelii is categorized as Critically Endangered on the 2002 IUCN Red List. Although several reports have suggested that the species occurs in the region to the south of Lake Toba in Sumatra, Indonesia, their distribution is poorly known. In order to determine whether orang-utans still occur in this region we surveyed areas in which orang-utans have been reported as well as a number of other forested areas. Orang-utan signs were found in only two areas. This indicates that habitat loss and hunting have recently caused local extinctions. We combine these results with other available information to provide a summary of the current distribution of P. abelii in Sumatra and, based on our surveys, previous population estimates, and estimates of losses, we speculate that only c. 3,500 orang-utans still occur in the wild in Sumatra at the end of 2002.

(Received January 14 2002)
(Revised June 5 2002)
(Accepted September 26 2002)


Key Words: Indonesia; Lake Toba; orang-utan; Pongo abelii; Primates; Sumatra.

Correspondence:
c1 Corresponding author Utrecht University, Behavioural Biology, P.O. Box 80086, 3508 TB, Utrecht, The Netherlands. Email: s.a.wich@bio.uu.nl


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