They use vegetation to construct nests for sleeping, which are usually only used once. Smaller nests may be made for daytime rests. Orangutans use leafy branches held over their heads or large leaves draped over their head and shoulders as protection from both rain and sun. Tool use among fully wild orangutans does not compare with that of chimpanzees, though captive orangutans released into the wild are quite adept at tool use. Ex-captives have been known to untie complex knots to untie boats and rafts, using them to cross rivers.
Males prefer mature females, and females prefer dominant males.
The estrous cycle is 30 days. The young clings to the ventral surface of the mother for about a year and may still ride on the mother at 2.5 years. Weaning is usually complete at 3.5 years. The interval between births is generally 3-4 years, though it can be as much as 8. Young may seek protection from their mother until they are about 7 or 8, at which time they are sexually mature.