Diet

The Bornean orangutan is an omnivore. The majority of their diet is fruit. They will move around their environment throughout the year to areas where fruit is in abundance. The rest of their diet is incredibly varied and may include leaves, shoots, bark, stems, flowers, sap, roots, insects, eggs, honey, birds and small lizards.

Sumatran orangutans eat a range of seeds which are then expelled in their poo and help to grow new trees.

Their water needs can be taken care of either from free water in tree hollows and on plants or from their food.

Range

Their natural home is Borneo in Asia. Borneo is an island shared between the countries of Malaysia, Indonesia and Brunei. They are confirmed to range through Malaysia or Indonesia. Their presence in Brunei is unknown. Fossil records suggest they previously ranged across the majority of the island but their distribution is now patchy.

They are unable to cross large rivers and these break up their range.

Habitat

Bornean orangutans are found in lowland and tropical rainforests, swamps, mountain forests and mosaic forests.

Up to 45% of their habitat is currently marked for conversion to agriculture representing a major threat to their future survival.

Reproduction

Breeding can take place year round with a peak around periods where fruit is most abundant.

A dominant male will maintain a home range which overlaps that of multiple females. He will call to announce his presence and females will come to mate with him. Only flanged males are dominant enough to maintain a home range but non-flanged males can still mate and will roam through females territories to mate with them.

Gestation is 8.5 months and following this a single young is born. On a rare occasion they can have twins.

They have an extremely long interbirth interval. Females look after the young for 6 years and will typically not give birth again until 8 years after their last pregnancy. This is the longest gap between infants of any known animal. This is a significant contributor to their endangered status as they are very slow to repopulate. Males have no involvement in raising the young.

Infants are dependent on the mother for all of their needs until 2 years old. Weaning off of milk takes place at around 4 years old.

Once they leave mum a female will immediately establish her own territory while males will need to wait till they are mature and can challenge other males to maintain their territory.

Females become sexually mature between 6 and 11 while males mature later at 8 to 15. Most males will not breed till their flanges develop around 15 years old.

Behavior

Bornean orangutans are primarily arboreal and spend the majority of their time in the trees. An exception to this is adult males who are so large that there is little natural threat on the ground. Their strong arms allow them to swing between trees and hang upside down for long periods while eating.

They are primarily solitary with most orangutans maintaining their own home range which they prevent others entering. On occasion females may meet at fruit trees and travel together for a short period of time.

Males vocalize a long call which can carry 1.9km (1.2miles) through the forest. This is used to attract mates and to alert other males to their presence and prevent them from entering their territory.

Predators and Threats

The only natural predator of the Bornean orangutan is the clouded leopard which can only prey on young individuals. They are also hunted by humans.

Bornean orangutans are one of the most endangered ape species and scientists suggest that they could be the first apes to go extinct.

They are threatened by logging, fires, palm oil plantations and hunting. Hunting takes place both for poaching of infants for the pet trade and capture for the bush meat trade.

Quick Facts

The orangutan is the only of the world’s four non-human great ape species found outside of Africa.

Orangutans are the largest arboreal (tree-climbing) animal on Earth.

The name orangutan is derived from Indonesian words which translate as ‘man of the forest.’