Distribution of Orangutans (Pongo pygmaeus) in Indonesia, from Orangutan Foundation International, 1997.
Map compiled by World Conservation Monitoring Centre.

WCMC data set compiled by Rachel Cook from the following sources:

Land cover data from WCMC / Asian Bureau for Conservation.
Wolfheim. J.H. 1982. Primates of the World, Abundance and Conservation. University of Washington Press.
Rijksen. H.D. 1978. A Field Study on Sumatran Orangutans. Wageningen.
Conservation Areas of Indonesia. 1991. Unpublished Report. WCMC.
Orang-utan Conservation in Sabah. Payne. J. 1988. WWF Malaysia Project 3759.
A Faunal Survey of Sabah. Davies. G. & Payne. J. 1982. WWF/IUCN Project 1692.
Sumatra's Orang-utans. Borner. M. 1976. Oryx. Volume Xiii No3.
Surveying Orang-utan Populations By Counting Nests From A Helicopter. 1986. WWF Project Malaysia.