The Bornean orangutan, Pongo pygmaeus, is a species of orangutan native to the island of Borneo. Together with the slightly smaller Sumatran orangutan, it belongs to the only genus of great apes native to Asia.
The Bornean orangutan has a life span of up to 35 years in the wild; in captivity it can live to be 60. A survey of wild orangutans found that males weigh on average 75 kilograms (170 lb), ranging from 50–100 kilograms (110–220 lb), and 1.2–1.4 metres (3.9–4.6 ft) long; females average 38.5 kilograms (85 lb), ranging from 30–50 kilograms (66–110 lb), and 1–1.2 metres (3.3–3.9 ft) long.
There is evidence that there was gene flow between the geographically isolated Bornean orangutan populations until recently. The Bornean oranguntan and Sumatran orangutan species diverged about 400,000 years ago. This occurred way before the two islands (Borneo and Sumatra) separated. The two species of orangutan are more distantly related than the common chimpanzee and the bonobo are. The two orangutan species were only considered subspecies until 1996, following sequencing of mtDNA.
The Bornean orangutan has three subspecies:
- Northwest Bornean orangutan P. p. pygmaeus - Sarawak (Malaysia) & northern West Kalimantan (Indonesia)
- Central Bornean orangutan P. p. wurmbii - Southern West Kalimantan & Central Kalimantan (Indonesia)
- Northeast Bornean orangutan P. p. morio - East Kalimantan (Indonesia) & Sabah (Malaysia)
The population currently listed as P. p. wurmbii may be closer to the Sumatran Orangutan (P. abelii) than the Bornean Orangutan. If confirmed, abelii would be a subspecies of P. wurmbii (Tiedeman, 1808). Regardless, the type locality of pygmaeus has not been established beyond doubts, and may be from the population currently listed as wurmbii (in which case wurmbii would be a junior synonym of pygmaeus, while one of the names currently considered a junior synonym of pygmaeus would take precedence for the taxon in Sarawak and northern West Kalimantan). To further confuse, the name morio, as well as various junior synonyms that have been suggested, have been considered likely to all be junior synonyms of the population listed as pygmaeus in the above, thus leaving the taxon found in East Kalimantan and Sabah unnamed.
The Bornean orangutan lives in tropical and subtropical moist broadleaf forests in the Bornean lowlands as well as mountainous areas 1,500 metres (4,900 ft) in elevation. It lives at different heights in the trees and moves large distances to find trees bearing fruit. Its diet consists of fruit as well as shoots, bark and bird eggs. It also eats insects but to a lesser extent than the Sumatran Orangutan. Bornean Orangutans have been sighted using spears to catch fish.
The Bornean orangutan travels on the ground more than its Sumatran counterpart. It is theorized this may be in part because there is no need to avoid the large predators which only exist in Sumatra such as the Sumatran Tiger.
Behavior and reproduction
The Bornean orangutan is more solitary than the Sumatran Orangutan. Two or three orangutans that have overlapping territories may only interact for short periods of time. Males and females generally only come together to mate. Sub-adult males (unflanged) will try to mate with any female and will be successful around half the time. Dominant flanged males will call and advertise their position to receptive females, who prefer mating with flanged males.
Newborn orangutans nurse every three to four hours, and begin to take soft food from their mothers' lips by four months. During the first year of its life, the young clings to its mother's abdomen by entwining its fingers in and gripping her fur. Offspring are weaned at four years, and at around five years they start their adolescent stage. During this period they will actively seek other young orangutans to play with and travel with.
The Bornean orangutan is more common than the Sumatran, with about 54,500 individuals in the wild; there are only about 6,600 Sumatran orangutans left in the wild. Orangutans are becoming increasingly endangered due to habitat destruction and the bushmeat trade, and young orangutans are captured to be sold as pets, usually entailing the killing of their mothers.
The Bornean orangutan is endangered according to the IUCN Red List of mammals, and is listed on Appendix I of CITES. The total number of Bornean orangutans is estimated to be less than 14 percent of what it was in the recent past (from around 10,000 years ago until the middle of the twentieth century) and this sharp decline has occurred mostly over the past few decades due to human activities and development. Species distribution is now highly patchy throughout Borneo: it is apparently absent or uncommon in the south-east of the island, as well as in the forests between the Rejang River in central Sarawak and the Padas River in western Sabah (including the Sultanate of Brunei). There is a population of around 6,900 in Sabangau National Park, but this environment is at risk. According to an anthropologist at Harvard University, it is expected that in 10 to 20 years orangutans will be extinct in the wild if there is no serious effort to overcome the threats that they are facing.
This view is also supported by the United Nations Environment Programme, which states in its report that due to illegal logging, fire and the extensive development of oil palm plantations, orangutans are endangered, and if the current trend continues, they will become extinct.
Rescue and rehabilitation centres
A number of orangutan rescue and rehabilitation projects operate in Borneo.
The Borneo Orangutan Survival Foundation (BOS) founded by Dr Willie Smits has rescue and rehabilitation centres at Wanariset and Samboja Lestari in East Kalimantan and Nyaru Menteng, in Central Kalimantan founded and managed by Lone Drøscher Nielsen. BOS also works to conserve and recreate the fast disappearing rainforest habitat of the orangutan, at Samboja Lestari and Mawas.
Orangutan Foundation International, founded by Dr Birutė Galdikas, rescues and rehabilitates orangutans, preparing them for release back into protected areas of the Indonesian rain forest. In addition, OFI promotes the preservation of the rain forest for the orangutans.
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