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.
