Bornean Orangutan

Bornean Orangutan

There are just over 40,000 orangutans left on the island of Borneo. But history has shown that population could decline rapidly if forest habitats continue to be destroyed at the current rate. Poaching also continues to be a threat to Borneon orangutan populations. WWF is actively involved in global efforts to protect habitat and halt the illegal trade in orangutans.

Key Facts

• Common names

  Bornean orangutan; Orangoutan de Borneo(Fr); Orangután de Borneo(Sp)
  

• Habitat

  Tropical and Subtropical Moist Broadleaf Forests
  

• Population

  Central Bornean = 38,000; NW Bornean = 3,000
  

• Status

  Endangered (EN - A2cd; IUCN) CITES: Appendix I
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Little resilience in the face of logging and fire

The Bornean orangutan is now recognised as a different species from its Sumatra relative. Three subspecies are recognized: Pongo pygmaeus pygmaeus, P.p. morio, and P. p. wurmbii, the most common Bornean subspecies. Although extensive, the latter's habitat is increasingly fragmented in the remaining swamp and lowland dipterocarp forests of Central and West Kalimantan.

It is estimated that about one third of Borneo's orangutan populations were lost during the 1997/ 98 forest fires. On the Indonesian side of Borneo, populations of this subspecies are not faring well either.

Although some populations live inside protected areas, illegal logging still takes place within these areas and hence remains a major threat to the survival of this species.

Major habitat type
Tropical and Subtropical Moist Broadleaf Forests

Biogeographic realm
Indo-Malayan

Range States
Indonesia, Malaysia

Geographical Location
Borneo

Ecological Region
Borneo Lowland and Montane Forests 

Ecology and Habitat

High quality habitat critical to birth-rate

Social Structure

Adult orangutans are generally solitary, although temporary aggregations are occasionally formed. The large home ranges of males overlap the ranges of several adult females. Adult males are generally hostile to one another, although they do not display territoriality.

Life Cycle

After weaning at about 3.5 years of age, young individuals become gradually independent of their mother after she gives birth to a second young. The age of first reproduction in the Borneo orangutan is around 10-15 years of age, but there may be differences between the various sub-species.

Breeding

Orangutans usually give birth to a single young, or occasionally twins, probably not more than once every five years. For the Bornean orangutan, the inter-birth interval can be as low as 5 years in high quality habitats.

The long period taken to reach sexual maturity, the long interbirth periods and the fact that orangutans normally give birth to just a single young mean that orangutans have an extremely slow reproductive rate. This makes orangutan populations highly vulnerable to excessive mortality, and means that populations take a long time to recover from population declines.

Diet

About 60% of the orangutan's diet includes fruit (e.g. durians, jackfruit, lychees, mangosteens, mangoes and figs), while the rest comprises young leaves and shoots, insects, soil, tree bark, woody lianas, and occasionally eggs and small vertebrates. They obtain water not only from fruit, but also from tree holes.

Priority Region

The Borneon orang-utan's habitat is part of the Heart of Borneo region, which is a WWF global priority region.

Population and Distribution

Kalimantan lost at least 39% of orangutan habitat within the species' range during 1992-2002

Previous population and distribution

A ten-year ongoing census of orangutans in the Sebangau Ecosystem recorded a 50% decline in numbers, from 12,000 individuals in 1995 to 6,000 in 2004. In Kutai National Park, perhaps only 10% of the area is still forested, and the orangutan population there was reduced from an estimated 4,000 in 1970 to 500 today.

Overall, analysis shows that Kalimantan (Indonesia) has lost at least 39% of its orangutan habitat within the orangutan's range over the 1992-2002 decade. 

Current population and distribution (click on map to the right to expand)

The Bornean orangutan is found in Kalimantan, and Sarawak and Sabah (Malaysia); most individuals occur in Kalimantan, where extensive areas of forest still exist, especially along the east coast.

The subspecies Pongo pygmaeus pygmaeus has been seriously affected by logging and hunting in its stronghold, Danau Sentarum, and a mere 1,500 individuals or so remain. Many swamps in the area are small, fragmented and are targeted by hunters. 

The largest population in Borneo is represented by Pongo pygmaeus wurmbii, especially in the large swamp areas of Central Kalimantan where at least 35,000 individuals are found. Major strongholds include Tanjung Puting, Sebangau and Arut-Belantikan, while an important population is found in Mawas, and a population further west in Gunung Palung. Elsewhere however, other once sizeable populations are disappearing fast.

The main stronghold of Pongo pygmaeus morio is the Berau/Gunung Gajah population, although remnants in what was once Kutai National Park may be worth protecting. New evidence suggests that P.p. morio has a strong presence in Sabah.

Densities and population sizes are in decline across the species range, and forest continues to be lost at a rapid rate.

Orangutan distribution on Borneo (Indonesia, Malaysia). The distribution of Orangutan on Borneo is rapidly decreasing, as humans reduce the available habitat for the apes. The loss of forest, through logging, clearing and burning, means reduced opportunities for hiding and food collection. In addition, orangutans are hunted for food and to be held in captivity.

Inspired by Krista Oragutan