3862 x 4555 px | 32,7 x 38,6 cm | 12,9 x 15,2 inches | 300dpi
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orangutans are a species of great apes. Known for their intelligence, they live in trees and they are the largest living arboreal animal. They have longer arms than other great apes, and their hair is reddish-brown, instead of the brown or black hair typical of other great apes. Native to Indonesia and Malaysia, they are currently found only in rainforests on the islands of Borneo and Sumatra, though fossils have been found in Java, the Thai-Malay Peninsula, Vietnam and China. They are the only surviving species in the genus Pongo and the subfamily Ponginae (which also includes the extinct genera Gigantopithecus and Sivapithecus). Adult male orangutans exhibit two modes of physical development, flanged and unflanged. Flanged adult males have a variety of secondary sexual characteristics, including cheek pads (called "flanges"), throat pouch, and long fur, that are absent from both adult females and from unflanged males. Flanged males establish and protect territories that do not overlap with other flanged males' territories. Adult females, juveniles, and unflanged males do not have established territories. A flanged male's mating strategy involves establishing and protecting a territory, advertising his presence, and waiting for receptive females to find him. Unflanged males are also able to reproduce; their mating strategy involving finding females in estrus and forcing copulation. Males appear to remain in the unflanged state until they are able to establish and defend a territory, at which point they can make the transition from unflanged to flanged within a few months. The two reproductive strategies, referred to as "call-and-wait" for flanged male and "sneak-and-rape" for the unflanged male, were found to be approximately equally effective in one study group in Sumatra, though this observation did occur during a period of instability in flanged male rank and unflanged male mating success may be lower in Borneo.
