Orangutan

Orangutans are great apes native to the rainforests of Indonesia and Malaysia. Today they are found only in parts of Borneo and Sumatra. There are three species: the Bornean orangutan, the Sumatran orangutan and the Tapanuli orangutan, and all three are critically endangered.

They are the most tree-dwelling of the great apes, with proportionally long arms and short legs and long reddish hair that starts bright orange and darkens to maroon or chocolate with age. The skin is grey-black. Females stand around 115 cm tall and weigh about 37 kg, while adult males stand around 137 cm and weigh about 75 kg. A male's arm span is about 2 m.

Dominant adult males develop large cheek pads called flanges, throat pouches and sometimes a beard. Sumatran orangutans are more slender, with paler, longer hair and a longer face. Tapanuli orangutans have shaggier hair, smaller skulls and flatter faces.

Orangutans belong to the genus Pongo and are the only surviving members of the subfamily Ponginae. They split from the African great ape line between about 19.3 and 15.7 million years ago. Their extinct relatives include apes found in China, Thailand, India and Pakistan, and the closest known relative is thought to be Khoratpithecus, which lived in Thailand 5-7 million years ago.

During the Pleistocene, orangutans ranged across Southeast Asia and South China. Their range shrank by the end of that period, most likely as forest habitat was reduced. Ancestors reached Sumatra and then Borneo across land bridges when sea levels were low.

They were long known to the native people of Sumatra and Borneo, who call them maias or mawas. Europeans learned of them in the 17th century. They were first described scientifically in the 18th century. They were originally treated as one species, split into two in 1996, and the Tapanuli orangutan was identified definitively in 2017. Most Western sources trace the name to Malay words meaning person and forest. Field studies by Biruté Galdikas, beginning in 1971, taught us much of what is known about their behaviour.

Orangutans are the most solitary of the great apes, though their society is described as solitary but social. Strong bonds occur mainly between mothers and their dependent young. Females live in overlapping home ranges within the range of a resident male. Flanged males are often hostile to other males, while places with plenty of fruit can draw gatherings of orangutans.

They spend the day feeding, resting and travelling: feeding for two to three hours in the morning, resting at midday and travelling in the late afternoon. Each evening they build a night nest from branches and foliage, sometimes with pillows and blankets. Fruit is the main food, but they also eat leaves, bark, honey, insects and bird eggs.

Dominant flanged males make long calls to attract females and warn off rivals. Orangutans are among the most intelligent primates. They use tools, such as sticks to extract insects and seeds, and different populations seem to have their own cultures.

Orangutans can live over 30 years, both in the wild and in captivity.

The most common parasites are nematodes of the genus Strongyloides and a ciliate called Balantidium coli. Strongyloides infections are reported in young individuals. Captive orangutans may suffer an upper respiratory tract disease.

Orangutans use a plant, Dracaena cantleyi, as an anti-inflammatory balm. In 2022 a male Sumatran orangutan was observed applying chewed vine leaves to a facial wound, which healed within a few weeks. Human activities have caused severe declines in their numbers.

This is general awareness only, not veterinary advice. If you find an injured or unwell wild animal, contact a vet or a wildlife rescue.

What is an orangutan?

Orangutans are great apes from the rainforests of Borneo and Sumatra. Most Western sources trace the name to Malay words meaning person and forest. They are the most tree-dwelling of the great apes.

How long do orangutans live?

They typically live over 30 years, both in the wild and in captivity. Females first give birth at around 15 and nurse young for up to eight years.

Are orangutans endangered?

Yes, all three species are critically endangered. Threats include deforestation for palm oil and logging, poaching and the illegal pet trade. Fewer than 800 Tapanuli orangutans are estimated to remain.

Are orangutans protected by law?

Yes. They are legally protected in Malaysia and Indonesia, and international law prohibits their unlicensed trade. The illegal pet trade is a major threat, and mothers are killed so infants can be sold.

Are orangutans social animals?

They are more solitary than the other great apes. Mothers and young stay close for years, but adults mostly live apart and meet at food-rich spots.

Orangutan mothers nurse their young for up to eight years, longer than any other mammal. Females also have the longest gap between births of any great ape, six to nine years.

They build a fresh nest each night, and young orangutans learn by watching their mothers.

Some orangutans have been seen poking sticks at catfish so the fish leap out of the water. Others use leaves to amplify their kiss squeak sounds.

Orangutans may eat soil, possibly for minerals that counter toxins in their diet.

A male orangutan's cheek pads are mostly fatty tissue, and his throat pouches act as resonance chambers for long calls. Males can delay developing these features until a dominant male is absent.

In central Borneo, some folk beliefs say it is bad luck to look an orangutan in the face.