Orangutans eat mostly fruits and nuts, but they may also eat leaves, bark, and insects. Males can be as large as 100 kg (220 lbs), and the females are about half that. Their armspan is usually longer than their height, which makes them most comfortable swinging from vines and sitting in the trees. Because of their dependence on trees, orangutans are threatened by the clearing of forests in their native Borneo and Sumatra.
Orangutans are born helpless and stay with their mothers to nurse for 6-7 years. Therefore, orangutan mothers only have a baby every 8-9 years. This is part of the reason that orangutans are so susceptible to extinction, because their population is slow to reproduce. Male orangutans are generally solitary creatures.
Orangutans are also pretty smart. They have been known to use tools to scratch their backs and to catch insects. They are also observant students and can be taught to communicate with sign language.