Orangutan

Orangutans are the only exclusively Asian genus of extant great ape. The largest living  arboreal animals, they have longer arms than the other, more terrestrial, great apes.  They are among the most intelligent primates and use a variety of sophisticated tools,  also making sleeping nests each night from branches and foliage. Their hair is typically  reddish-brown, instead of the brown or black hair typical of other great apes.Native to Indonesia and Malaysia, orangutans 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 Mainland China. There are only two surviving species,  both of which are endangered: the Bornean Orangutan (Pongo pygmaeus) and the  critically endangered Sumatran Orangutan (Pongo abelii). The subfamily Ponginae also  includes the extinct genera Gigantopithecus and Sivapithecus. The word “orangutan”  comes from the Malay words “orang” (man) and “(h)utan” (forest); hence, “man of the forest”.

Orangutans live a more solitary lifestyle than the other great apes. Most social bonds occur between adult females and their dependent and weaned offspring. Adult males and independent adolescents of both sexes tend to live alone. The society of the orangutan is made up of resident and transient individuals of both sexes. Resident females live with their offspring in defined home ranges that overlap with those of other adult females, who may be their relatives like mothers and sisters. One to several resident female home ranges are encompassed within the home range of a resident male, who is their primary breeder.  Transient males and females range broadly.  They usually travel alone, but as sub-adults they may travel in small groups. However this behavior does not extend to adulthood. The social structure of the orangutan can be best described as solitary but social. As the ranges of males and females overlap, they commonly encounter each other while traveling and feeding and may have brief social interactions.Interactions between adult females range from friendly, to avoidance to antagonistic. Resident males may have overlapping ranges and interactions between them tend to be hostile.

During dispersal, females tend to settle in home ranges that overlap with their mothers. However, they do not interact when them any more than the other females and they do not seem to form bonds though affiliation, grooming, or agonistic support. Males disperse much farther from their mothers and enter into a transient phase. This phase lasts until a male can challenge and displace a dominant, resident male from his home range.There are dominance hierarchies between adult males that regularly encounter each other with the most dominant males being the largest and having the best body conditions. Adult males dominate sub-adult males. Both resident and transient orangutans aggregate on large fruiting trees to feed. The fruits tend to be abundant, so competition is low and individuals may benefit from social contacts. Orangutans will also form travelling groups in which members coordinate travel between food sources for a few days at a time. These groups tend to be made of only a few individuals. They also tend to be mating consortships, each made of an adult male and female traveling and mating.