Bornean Orang-utan (Pongo pygmaeus)

Bornean Orang-utan. Photo © Chris Perrett.

The Bornean Orang-utan is the largest tree-dwelling mammal in the world. Females reach an average height of 1 – 1.2m and weigh around 40kg, whilst males are slightly larger, up to 1.4m in height and between 50 – 90 kg. Males develop cheek pads on the side of their faces, the size of which determine their age.

Orang-utans occur in Indonesian and Malaysian Borneo and can live for up to 35-40 years in the wild. The name orang-utan originates from the Malay orang hutan which literally means ‘person of the forest’.

Orang-utans differ from other great apes in several ways:

• Their hair is reddish orange rather than the more common black and brown;
• Their arms are much longer relative to the legs than in other ape species - twice as long as the legs;
• They are semi-solitary whilst most other ape species live in large social groups.

Behaviour

Orang-utans spend almost their whole lives in the tree tops, rarely descending to the forest floor. They feed mostly on fruit, but also leaves, bark and termites when food is scarce. They use their arms and legs to swing between trees in the forest canopy and build a nest to sleep in each night, usually in a fork of two branches.

Female orang-utans give birth to one offspring every 8 years on average. The mother will carry her infant around for the first 2-3 years of its life and it will remain with her for up to 7 years.

Habitat and ecology

The Bornean Orang-utan is restricted to the Island of Borneo, although it is believed they were once widely distributed across South East Asia. Orang-utans are hugely dependant on continuous forest cover with a male orang-utan covering up to 4,000 hectares in his lifetime. This also means that orang-utans play a vital role in forest regeneration as they act as seed dispersal agents and create light gaps when they move through the forest canopy.

Status and conservation

Young orang-utan in a rehabilitation centre, Borneo. Click on the image to see a larger version.

The Bornean Orang-utan is more common than its relative, the Sumatran Orang-utan, with an estimated 45,000 individuals in the wild. In the past baby orang-utans were captured for sale in the pet trade, but they are now protected by law in both Malaysian and Indonesian areas of Borneo.

The protection of Orang-utans is closely linked to the protection of their habitat due to their dependence on the forest. Borneo's forests are threatened by illegal logging, gold mining and agriculture, particularly oil palm plantations. In just 20 years, orang-utan habitat have become reduced by 80%. The Bornean Orang-utan is therefore classified as Endangered. (See the IUCN Red List for more information on the classification of the Bornean Orang-utan.)

Help Protect the Orang-utan and Other Wildlife in Borneo

Orang-utans can be found living in the World Land Trust project area in Borneo.
Please help protect orang-utan habitat: Support our urgent Orang-utan Appeal.