The Bornean orangutan (Pongo pygmaeus) is a species of orangutan endemic to the island of Borneo. Together with the Sumatran orangutan (Pongo abelii) and Tapanuli orangutan (Pongo tapanuliensis), it belongs to the only genus of great apes native to Asia. Like the other great apes, orangutans are highly intelligent, displaying tool use and distinct cultural patterns in the wild. Orangutans share approximately 97% of their DNA with humans. Also called mias by the local population, the Bornean orangutan is a critically endangered species, with deforestation, palm oil plantations, and hunting posing a serious threat to its continued existence.
The Bornean orangutan lives in tropical rain forests in the Bornean lowlands, as well as montane rain forests in mountainous areas up to 1,500 metres (4,900 ft) above sea level. This species lives throughout the canopy of primary and secondary forest, and moves large distances to find trees bearing fruit.
It is found in the two Malaysian states of Sabah and Sarawak, and four of the five Indonesian Provinces of Kalimantan. Due to habitat destruction, the species distribution is now highly patchy throughout the island, the species has become rare in the southeast of the island, as well as in the forest between the Rajang River in central Sarawak and the Padas River in western Sabah. Its presence in Brunei is uncertain and unconfirmed.
In history, orangutans ranged throughout Southeast Asia and into southern China, as well as on the island of Java and in southern Sumatra. They primarily inhabit peat swamp forest, tropical heath forest, and mixed dipterocarp forest. Bornean orangutan are more solitary than their Sumatran relatives. Two or three orangutans with overlapping territories may interact, but only for short periods of time. Although orangutans are not territorial, adult males will display threatening behaviors upon meeting other males, and only socialize with females to mate. Males are considered the most solitary of the orangutans. The Bornean orangutan has a lifespan of 35–45 years in the wild; in captivity it can live to be about 60.
Despite being arboreal, the Bornean orangutan travels on the ground more than its Sumatran counterpart. This may be in part because no large terrestrial predators could threaten an orangutan in Borneo. In Sumatra, orangutans must face predation by the fierce Sumatran tiger.
The Bornean orangutan exhibits nest-building behavior. Nests are built for use at night or during the day. Young orangutans learn by observing their mother's nest-building behaviour. This skill is practiced by juvenile orangutans. Nests may be elaborate and involve a foundation and mattress made by intertwining leaves and branches and adding broken leafy branches. Additional features such as shade, waterproof roof, "pillow", and "blanket", all of which are made from branches, twigs and leaves, may also be added. Nest-building in primates is considered as an example of tool use and not animal architecture.
The Bornean orangutan diet is composed of over 400 types of food, including wild figs, durians (Durio zibethinus and D. graveolens), leaves, seeds, bird eggs, flowers, sap, vines, honey, fungi, spider webs, insects, and, to a lesser extent than the Sumatran orangutan, bark. They have also been known to consume the inner shoots of plants and vines. They will also occasionally eat nutrient rich soil. They get the necessary quantities of water from both fruit and from tree holes.
