Friday, January 18, 2013

The Bornean Orangutan

            The Bornean Orangutan (Pongo pygmaeus) is one of only two species of Orangutan, which together are the only species of great apes to be found in Asia, and Orangutans are the largest tree-dwelling mammals in the world. Orangutans have a distinctive body shape, with very long arms that may reach up to two metres in length. They have a coarse, shaggy, reddish coat and grasping hands and feet. The skin of the face is bare and black, but can be pinkish around the eyes and muzzle in younger individuals.

            Orangutans are highly sexually dimorphic, with adult males being distinguished from females by their larger size. The adult male Bornean Orangutan occurs in two forms, flanged or unflanged. Flanged males are larger than unflanged males, and also differ in possessing fleshy, protruding ‘flanges’, or cheek pads, on either side of the face. The transition from the unflanged to the flanged form can happen anytime; this depends mostly on complex social cues that are not yet fully understood.

Did You Know
            Bornean Orangutans build nests from bent branches high up in the trees where they sleep at night. On average, female Orangutans only give birth every eight years, making them the slowest breeding of all mammal species.

Scientific Classification


Other Names

Bornean Orang-utan
Orang-outan De Bornéo

            The Bornean Orangutan is classified as Endangered (EN) on the IUCN Red List, and listed on Appendix I of CITES.


            The Bornean Orangutan 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 Bornean Orangutan lives in tropical and subtropical moist broadleaf forests in the Bornean lowlands, as well as mountainous areas up to 1,500 metres above sea level. This species lives throughout the canopy of primary and secondary forests, and moves large distances to find trees bearing fruit.

            The Bornean Orangutan is endemic to the island of Borneo where it is present in the two Malaysian states of Sabah and Sarawak, as well as in three of the four Indonesian Provinces of Kalimantan. Species distribution is now highly patchy throughout the island: it is apparently absent or uncommon in the south-east of the island, as well as in the forests between the Rejang River in central Sarawak and the Padas River in western Sabah (including the Sultanate of Brunei).

            Three subspecies are currently recognised, and their ranges are as follows; 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


           Orangutans are semi-solitary animals, but complex social networks of loose relationships are maintained between members of a community. More than 500 plant species have been recorded in their diet. Fruits make up more than 60% of their average total intake. The diet also includes leaves, barks, flowers and insects. Orangutans are best described as “gardeners” of the forest as they play a vital role in seed dispersal. Fruit availability in the Bornean forest directly impacts all aspects of their life: ranging patterns, seasonal movements, health, social and reproductive behaviour.

            Females generally give birth to a single infant after a gestation period of approximately 245 days (Nowak 1999). Female Bornean Orangutans reach maturity between 10 and 15 years old and reproduce every six to eight years on average making them the slowest reproducing mammal.


The total number of Bornean Orangutans is estimated to be less than 14% of what it was in the recent past (from around 10,000 years ago until the middle of the twentieth century) and this sharp decline has occurred mostly over the past few decades due to human activities and development.

Major threats include:

Habitat losses with the destruction of vast areas of tropical forest throughout the island and their conversion to agriculture (mostly oil palm plantations - Elaeis guineensis, but also acacia, rice, subsistence crops, cocoa, etc). An overall loss of 15.5 million hectares of forest (24% of total forest area) was recorded between 1985 and 1997 in Sumatra and Kalimantan, while 37% of the total forest area was lost in Sabah between 1950 and 2000. In the lowlands (prime Orangutan habitat) this figure is higher and reaches more than 60%.

Fires, The El Niño climatic event has been occurring repeatedly in the last few decades, and is associated with severe droughts and forest fires. Ninety percent of Kutai National Park was lost to massive fires in 1983 and 1998 and its Orangutan population was reduced from an estimated 4000 individuals in the 1970s to a mere 500 today. Over 400,000 ha of peatland forest in South Kalimantan were burnt to ashes in six months during 1997-98, representing an estimated loss of 8,000 Orangutans. As a result of the 1997-98 fires, we estimate that the Bornean Orangutan population was reduced by 33% in just one year.

Habitat exploitation and illegal logging It is well established that more aggressive and conventional logging practices have a negative impact on Orangutan populations. Rampant legal and illegal logging results in the destruction of key food sources that sustain Orangutans, and in the fragmentation of remnant sub populations which subsequently become more prone to local extinction and catastrophes.

Hunting and Pet Trade In some parts of the island, hunting has been a major threat and is directly responsible for local extinctions. Major reasons for hunting include: bush meat trade, wanton killing as part of poaching for other forest products use of body parts for traditional medicine and pet trade. Illegal export of animals continues. In early 2004 about 100 individuals of Bornean origin were confiscated in Thailand and 50 of them were repatriated to Kalimantan in 2006

Conservation Measures

            The Bornean Orangutan 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. While some populations do occur within protected parks, illegal logging even within protected areas remains a key threat to the survival of this species, and has increased with political instability in Indonesia.

            Current conservation priorities for the Bornean Orangutan include the long-term protection its forest habitat. In order to ensure their long term success, conservation projects need to involve local communities that occur in close proximity to Orangutan habitat. Conservationists are also working to reduce conflict between people and Orangutans, by devising practical solutions to prevent Orangutans from raiding crops. Captive Bornean Orangutans, often rescued from the illegal wildlife trade, are being re-introduced into the wild in rehabilitation centres.



  1. i think the people who wrote this deserve Nobel prizes.i am not kidding.

  2. i wish that the hunters would drop dead

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