Bornean orangutan

High-quality habitat is critical

While Bornean orangutans appear tolerate habitat disturbance better than Sumatran orangutans, the species breeds much faster in high-quality habitat.

Social structure
Adult orangutans are generally solitary, although temporary aggregations are occasionally formed. 

Although arboreal, Bornean orangutans (especially adult males) more often descend to the ground than Sumatran orangutans.
 

Population & distribution

Previous population & distribution
The Bornean orangutan was once distributed throughout large areas of Kalimantan (Indonesia) and Sarawak and Sabah (Malaysia) on the island of Borneo, but typically at a relatively low abundance.

Three subspecies are recognized, localized to different parts of the island (see map to the right):

• P. p. pygmaeus
• P. p. morio
• P. p. wurmbii (the most common subspecies).

Current population & distribution
Both numbers and distribution have declined rapidly since the middle of the 20th century, due to human activities. These include hunting, unsustainable and often illegal logging, mining, and conversion of forests to agriculture. One particularly catastrophic event was the 1997/ 98 forest fires in Kalimantan, which killed up to 8,000 individuals.

Overall, numbers of Bornean orangutans have declined by more than 50% over the past 60 years, while the species' habitat has been reduced by at least 55% over the the past 20 years.

Most Bornean orangutans are now found in Kalimantan, where extensive areas of forest still exist, especially along the east coast. The majority of  wild populations are located outside of protected areas, in forests that are exploited for timber production or in the process of being converted to agriculture. 

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

• The most numerous subspecies, P. p. wurmbii, is primarily found in the large swamp and lowland dipterocarp forest areas of Central Kalimantan, where at least 35,000 individuals survive. 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. However, while still extensive, this habitat is becoming increasingly fragmented. Elsewhere, other once sizeable populations are disappearing fast.
   
• P. p. pygmaeus is the most endangered subspecies. Core populations are found in four protected areas in western Borneo: Lanjak Entimau, Batang Ai, Danau Sentarum and Betung Kerihun. Its stronghold, Danau Sentarum, has been seriously affected by logging and hunting, and a mere 1,500 individuals or so remain. Many swamps in the area are small, fragmented and targeted by hunters. 
   
• The main stronghold of P. p. 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.

What are the main threats?

Habitat loss and degradation
While Bornean orangutans appear to survive in logged habitat at lower densities – and while some such populations remain surprisingly substantial – habitat loss nevertheless continues to threaten the species.

Massive land conversion projects such as the disastrous Mega-Rice Project in Kalimantan demonstrate how rapidly areas of orangutan habitat can be destroyed. One million hectares of peat-swamp forest was partly cleared and drained during 1995-97 for conversion to rice fields, despite the inadequacy of the land for agriculture.

• More on habitat loss and degradation

Habitat disappearing even in protected areas
The boundaries of protected areas in Borneo are often not clearly delineated, which makes them difficult to patrol. Furthermore, many parks are understaffed and underfunded. Consequently, shifting cultivators, oil palm companies and logging concessions have encroached into all the parks. 

Illegal logging has been controlled to some extent in Tanjung Puting and Gunung Palung National Parks. However, illegal logging and other damaging human activities occur in the four protected areas housing P.p. pygmaeus, the most endangered subspecies. 

Collateral damage
Collateral problems associated with habitat loss include the spread of fire, hunting and human-animal conflict.

For example, the drainage of peat-swamp forest mentioned above contributed to uncontrollable fires in Kalimantan in 1997/98, which lasted for 6 months. Due to clearing of vast tracts of the surrounding forests, almost no forest remained for orangutans to seek refuge in, and land changes prevented them from escaping. It is thought that up to 8,000 individuals could have perished in the fires.

Hunting
Orangutans are hunted for food in some areas. Hunting intensity seems to vary from one region to another, a phenomenon probably explained by cultural and religious differences. However, even the slightest hunting pressures can cause a steep decline in numbers, even in good quality habitat. 

Hunting is the likely cause of the very low estimated densities of orangutans in low-hill forests, particularly in the upper reaches of the Katingan and Barito rivers in Central Kalimantan and Pawan river in West Kalimantan. 

Conflict with humans
The animals are also sometimes shot in retaliation when they move into agricultural areas, such as oil palm plantations, and destroy crops. This occurs particularly in times of hardship when orangutans can’t find the food they need in the forest.

Pet trade
Young orangutans are in demand for a flourishing pet trade, with each animal fetching several hundred dollars in city markets in nearby islands such as Java.

Studies have indicated that 200-500 orangutans from Indonesian Borneo alone enter the pet trade each year. In order to obtain live young orangutans, poachers must at least kill the mother, so this trade represents a real threat to wild orangutan populations.

There is also trade in dead orangutan parts in Kalimantan, with orangutan skulls fetching up to US$70 in towns.

• More on wildlife trade

You can help

• Adopt an orangutan through WWF-UK or WWF-US and support our work to protect orangutans (international adoptions possible)
   
• Buy sustainable wood, paper and palm oil. By purchasing certified sustainable palm oil and FSC-certified forest products, consumers, retailers, traders, and manufacturers help protect orangutan habitat by limiting illegal logging and forest conversion to oil palm plantations. 
   
• Spread the word! Click on the button to share this information with others via email or your favourite social networking service.