Bornean orang-utan  (Pongo pygmaeus)

Orang-utan means 'person of the forest' (4) and this Asian ape is indeed truly a tree-dweller. Recent genetic evidence has led to the re-classification of Bornean and Sumatran orang-utans as separate species: Pongo pygmaeus and Pongo abelii respectively (5). Orang-utans have distinctive body shapes with very long arms that may reach up to two metres in length. They have a coarse, shaggy reddish coat (6) and grasping hands and feet (2). They are highly sexually dimorphic, with adult males being distinguished by their large size, throat pouch and flanges on either side of the face, known as cheek pads (7).

Fossil evidence suggests that orang-utans were once widely distributed in South East Asia, but the Bornean orang-utan is today restricted solely to the island of Borneo with the largest population located in Kalimantan, the Indonesian part of the island (8). Three subspecies are recognised; P. p. pygmaeus ranges from northwest Kalimantan to Sarawak, P. p. wurmbi occurs on southwest Kalimantan, and P. p. morio can be found on northeast Kalimantan to Sabah (1) (7).

Mainly inhabits lowland and hilly tropical rainforests (2), up to 800 meters above sea level (7).

Bornean orang-utans are predominantly solitary, occupying large overlapping home ranges. The largest arboreal mammal, they spend almost all of their time in the trees, clambering between branches or using their body weight to bend and sway trees (2). Each night a nest is built from bent branches, high up in the trees (5).

Orang-utans are the slowest breeding of all mammal species, with an inter-birth interval of approximately eight years (7). They are long-lived and females tend to only give birth after they reach 15 years of age. The infant spends its first two to three years being carried constantly and will still remain close to the mother for at least another three years (7).

The orang-utan diet is composed of over 400 types of food, including wild figs (Ficus spp.) and durians (Durio spp.) (7). When fruit is scarce however, orang-utans will feed on leaves, seeds and even bark (5).

Orang-utans were hunted relentlessly in the majority of their South East Asian range, their large size and slow movements making them easy targets for hunters (9). However, the main threat to orang-utans today is loss of habitat. In the past twenty years, 80 percent of orang-utan habitat has been lost to illegal logging, gold mining and conversion to permanent agriculture, in particular, palm oil plantations. These animals are extremely vulnerable to exploitation, largely as a result of their extremely long inter-birth interval (7).

Forest fires raged through much of Borneo in 1997 and 1998 and it is estimated that around one third of the island's orang-utan population was lost at this time (9). Orang-utans that wander into palm oil plantations and other human-inhabited areas may also be captured for the illegal pet trade, although this is a by-product of shrinking habitat and not a main issue (7).

The Bornean orang-utan is protected by law in both the Malaysian and Indonesian areas of the island, and is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which prohibits international trade (8). Populations also occur within a number of protected parks, although illegal logging even within protected areas remains a key threat to the survival of this species, and has increased with political instability in Indonesia (2). Captive individuals are re-introduced into the wild in three rehabilitation centres in Kalimantan, one in Sabah and one in Sarawak (7). Time is running out for the Asian ape however, and there are fears that at current rates of decline, both the Sumatran and the Bornean orang-utan could be extinct in the wild by 2010 (9). Due to the large home ranges that these apes require it is the protection of habitat that will ensure that these beautiful and enigmatic 'people of the forest' survive into the next century (7).

For further information on the Bornean orang-utan see:

• The Great Apes Survival Project (GRASP):
  www.unep.org/grasp/
• The Orangutan Foundation:
  www.orangutan.org.uk
• The Bornean Orangutan Survival Foundation:
  www.savetheorangutan.info/

Information authenticated by Martha Lorenz of the Orangutan Foundation.
http://www.orangutan.org.uk