Orangutans are the only great apes found outside of Africa. There are two orangutan species and the Sumatran orangutan is the more endangered of the two. It differs from its Borneo relative to some extent in appearance and behavior. Found mainly in the northern and western provinces of Sumatra, Indonesia, the species is fast losing its natural habitat to agriculture and human settlements.

There are an estimated 6,500 orangutans left on Sumatra, in 10 identified populations on the island. Of those, probably only six contain more than 250 individuals, with just three of those containing more than 1,000 individuals.

According to IUCN, Sumatran orangutan populations are believed to have declined more than 80 percent in the past 75 years and are classified as critically endangered. During 1998 and 1999, losses are reported to have reached a rate of about 1,000 orangutans per year in the Leuser Ecosystem alone, one of the largest tracts of forest in the volatile northern part of the island.