The orangutans are the two exclusively Asian species of extant great apes. Native to Indonesia and Malaysia, orangutans are currently found only in the rainforests of Borneo and Sumatra. Classified in the genus Pongo, they comprise two species: the Bornean orangutan (P. pygmaeus) and the Sumatran orangutan (P. abelii).
Orangutans are Asia's largest primates, and males are larger than females. Males stand about four and a half feet tall and weigh 130 to 200 pounds. Females stand about four feet tall and weigh 90 to 110 pounds. Zoo animals are often heavier.
Orangutans feed primarily on forest fruits, including durians, jackfruits, lychees, mangos, and figs. Leaves and shoots make up the remainder of their diet, supplemented occasionally by small animals, tree bark, and soils rich in minerals. Researchers have documented more than 400 different foods eaten by wild orangutans.
Orangutans spend in different activities varies depending on the availability of food, social conditions, and reproductive status. On average, orangutans spend approximately 44% of their time resting, 41% feeding, 13% traveling, 2% nest building, and less than 1% engaging in other activities, such as fighting, mating, and socializing. Because orangutans are primarily solitary, their activity patterns may be very individualistic.
The destruction and degradation of the tropical rain forest, particularly lowland forest, in Borneo and Sumatra is the main reason orangutans are threatened with extinction. This has been caused primarily by human activity (intense legal logging, illegal logging, conversion of forest to palm oil plantations and timber estates, mining, clearing forest for settlements, and road construction) and also by large-scale fires facilitated by the El Nino weather phenomena. Additionally, the illegal animal trade has been a factor in the decline of wild orangutan populations. Finally, orangutans are occasionally hunted and eaten by some of the indigenous peoples of Borneo as well as migrant loggers and plantation workers who do not have dietary prohibitions against eating primate bushmeat.
Like humans, orangutans have opposible thumbs. Their big toes are also opposible. Unlike humans, approximately one third of all orangutans do not have nails on their big toes.
While other apes might go from tree to tree searching for fruit, an orangutan will just sit in the forest canopy for hours on end until the location of the hidden fruit seems to mysteriously reveal itself. Then it will swing over for its meal. Orangutans have even been known to watch villagers use boats to cross the local waterways, and then untie a boat and ride it across the river on their own!
The orangutan genome adds detail to the evolutionary tree and gives scientists insights into the unique aspects of human DNA that set man apart from the great apes, their closest relatives. Overall, the researchers found that the human and orangutan genomes are 97 percent identical.
The male great call has been documented as being heard up to 800 m away. It is used to define territories between flanged males, to coordinate group movements and cohesiveness, and to attract females. Only flanged males call; unflanged males, which are lower in status than flanged males, may be tolerated by flanged males in their territories.
Because of the semi-solitary nature of orangutans, adult males have no contact with infants and therefore no parental investment in the wild. The orangutan mother is the primary care provider and instrument of socialization for her offspring. The strongest, most salient social group among orangutans involves an adult female and her dependent offspring. Because an adult female is likely to have more than one offspring with her (an older adolescent and an infant), older siblings can be very important in socializing infants and juveniles (Munn & Fernandez 1997).