Young Sumatran orangutan (Pongo abelii). The orangutan is an arboreal (tree-dwelling) great ape endemic to Sumatra. It is a solitary animal, meeting others only to mate, although females and their young may stay together for several years. An adult male does not seem to have a defined territory, and never fights other males. The orangutan's diet consists mainly of fruit and insects. Photographed in Gunung Leuser National Park, Sumatra, Indonesia.