ABSTRACT
Orangutans are the great apes of Asia and highly arboreal despite their large size. They are the most sexually dimorphic living primates except for mandrills. The descriptions of primate behavior are arranged under four headings: ecology, sociality, life cycle, and cognition. Orangutan social interactions are more limited than in any other anthropoids. Both sexes use tools that provide evidence for cognition and culture. Forced copulations occur and dominant males may provide protection from sexual harassment. Orangutans have low infant mortality and very slow life history. Male home ranges are at least three times larger than those of females. Some males were called wanderers, supposedly having no fixed association with place. Unflanged males sometimes display affiliative behavior, such as play and isosexual interactions. They may associate with females at the same time with no conflict between them. Male vulnerability is an important feature of orangutan life history. Orangutans learn quickly from other animals and from humans.
