Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Hominidae

Scientific Name: Pongo pygmaeus
Species Authority: (Linnaeus, 1760)
Infra-specific Taxa Assessed:
Common Name(s):
English Bornean Orangutan
French Orang-outan De Bornéo
Spanish Orang-után
Taxonomic Notes: The Asian primate classification recently published by Brandon-Jones et al. (2004) recognized only two subspecies for the Bornean Orangutan: P. p. pygmaeus and P. p. wurmbii. However, at the last orangutan PHVA (Singleton et al. 2004), an additional subspecies was recognized: Pongo pygmaeus morio.

Warren et al. (2001) used the control region of the mitochondrial DNA on six different Bornean populations and identified four distinct subpopulations with particular regional diversity and geographic clustering: (1) Southwest and Central Kalimantan; (2) Northwest Kalimantan and Sarawak; (3) Sabah; and (4) East Kalimantan. If we correlate those four subpopulations with the three subspecies described above, we have P. p. pygmaeus in (1), P. p. wurmbii in (2) and P. p. morio in (3) and (4).

P. p. pygmaeus: Northwest Bornean Orangutan:
- Sarawak (Malaysia)
- Northwest Kalimantan (Indonesia)

P. p. wurmbii: Central Bornean Orangutan:
- Southern west Kalimantan
- Central Kalimantan (Indonesia)

P. p. morio: Northeast Bornean Orangutan:
- East Kalimantan (Indonesia)
- Sabah (Malaysia)

Assessment Information [top]

Red List Category & Criteria: Endangered A2cd+3cd+4cd ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Ancrenaz, M., Marshall, A., Goossens, B., van Schaik, C., Sugardjito, J., Gumal, M. & Wich, S.
Reviewer(s): Mittermeier, R.A. & Williamson, E.A. (Primate Red List Authority)
There has been an estimated decline of orangutan well over 50% during the last 60 years (generation length estimated at 20 years, Wich et al. in press). The decline of the species is predicted to continue at this rate, primarily because of forest loss due to conversion of forest to agriculture and fires. The majority of remnant 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. Last but not least, poaching and the pet-trade remain major threats to orangutans across most of Borneo.
Previously published Red List assessments:
2007 Endangered (EN)
2000 Endangered (EN)
1996 Vulnerable (VU)
1994 Endangered (E)
1990 Endangered (E)
1988 Endangered (E)
1986 Endangered (E)
1965 Very rare and believed to be decreasing in numbers

Geographic Range [top]

Range Description: 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).
Countries occurrence:
Indonesia (Kalimantan); Malaysia (Sarawak)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The most recent estimates for Bornean orangutan numbers are between 45,000 and 69,000 individuals living in 86,000 km² of suitable habitat (Singleton et al. 2004, Caldecott and Miles 2005). These estimates were obtained between 2000 and 2003. Since recent trends are steeply down in most places due to logging and burning, it is forecasted that the current numbers are below these figures (Tables 1a, b and c, in supplementary material).

See the supplementary material for Tables 1a, b and c: population size estimates for P. p. wurmbii, P. p. pygmaeus and P. p. morio.
For further information about this species, see 17975_Pongo_pygmaeus.pdf.
A PDF viewer such as Adobe Reader is required.
Current Population Trend: Decreasing
Additional data:
Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: Orangutans are the largest arboreal mammals found on earth today. They are semi-solitary animals, but complex social networks of loose relationships are maintained between members of a community. Males tend to disperse further than females at maturity. More than 500 plant species have been recorded in their diet. Fruits make up more than 60% of their average total intake (Wich et al. 2006). The diet also includes leaves, barks, flowers and insects. Orangutans are best described as “gardeners” of the forest (Rijksen and Meijaard 1999); they play a vital role in seed dispersal, especially for large seeds that are not dispersed by smaller animals (Ancrenaz et al. 2006). Fruit availability in the Bornean forest directly impacts all aspects of their life: ranging patterns, seasonal movements, health, social and reproductive behaviour.

The orangutan is the only primate species with two different forms of mature males (bimaturism). Flanged males are twice the size of the female; they possess a long coat of dark hair on the back, a facial disk, flanges and a throat sac used for “long calls”. These males are rather intolerant and aggressive towards other adult males. Unflanged males do not possess these secondary sexual characteristics; they are the size of an adult female, they do not emit long calls nor do they show mutual intolerance. These two types of male both sire offspring and contribute to the reproduction of a given population (Goossens et al. 2006a). 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.

Bornean orangutan distribution is patchy throughout the island. Large rivers are impassable natural barriers and limit their dispersal (Goossens et al. 2005). The species occurs typically at relatively low abundance in the Bornean forests: from 0.5 to 4.0 ind./km² in most populations (review in Singleton et al. 2004, van Schaik et al. 2005). Bornean orangutans are more abundant in low-lying forests (below 500 meters asl) than in uplands. Flood-prone forests and peatswamps produce more regular and larger fruit crops than dry dipterocarp forests and harbour the highest orangutan densities. Bornean orangutans are vulnerable to habitat disturbances, although the taxon P. p. morio shows a relative and unexpected tolerance to habitat degradation in the northern part of the island (Ancrenaz et al. 2005).

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 (Nowak 1999, Wich et al. in press).
Systems: Terrestrial

Threats [top]

Major Threat(s): 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 (Singleton et al. 2004, Goossens et al. 2006b).

Major threats include:

1. 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 (FAO 2000). In the lowlands (prime orangutan habitat) this figure is higher and reaches more than 60% (Holmes 2000). We consider that today only 86,000 km² of habitat remains available to the species throughout the island (which is about 740,000 km²). Protected areas home to significant orangutan populations are also threatened by habitat loss (Curran et al. 2003).

The rapid expansion of oil palm plantations in Borneo in response to international demand (the oil is used for cooking, cosmetics, mechanics, and more recently as source of bio-diesel) has accelerated habitat losses. Between 1984 and 2003, the area planted with palm oil on Borneo increased from 2,000 km² to 27,000 km²: about 10,000 km² is located in Kalimantan; 12,000 km² in Sabah and 5,000 km² in Sarawak. Many areas used to be prime habitat for the orangutans: eastern lowlands of Sabah, the plains between the Sampit and Seruyan rivers in central Kalimantan, etc.

2. 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 (Rijksen and Meijaard 1999). Over 400,000 ha of peatland forest in South Kalimantan were burnt to ashes in six months during 1997-98 following the collapse of the Mega-Rice project, representing an estimated loss of 8,000 orangutans (Page et al. 2002). Large numbers of orangutans are also killed by people while fleeing the flames and smoke during and after the fires. As a result of the 1997-98 fires, we estimate that the Bornean orangutan population was reduced by 33% in just one year. The most recent drought of 2006 in Kalimantan is thought to have killed several hundred orangutans in just six months. Forest fires can also result in the arrival of “refugees” in surrounding remnant and the resulting crowding effect can have serious negative impacts on the resident population (Husson et al. 2005).

3. Habitat exploitation and illegal logging. Although recent work in Sabah and East Kalimantan shows that orangutans can adapt and survive (at least in the short term) in commercial forest reserves exploited for timber according to sustainable logging practices (reduced-impact logging; FSC certification), 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 subpopulations which subsequently become more prone to local extinction and catastrophes.

4. Habitat fragmentation. Recent results from the orangutan PHVA show that Bornean orangutan populations of fewer than 50 individuals are not viable in the long-term and will most probably go extinct in the next 100 years (Singleton et al. 2004, Marshall et al. in prep.). Forest fragmentation further reduces the size of orangutan populations and makes them more prone to genetic drift and inbreeding as well as to local catastrophes, such as floods, fires, outbreak diseases, hunting pressure.

5. Hunting. In some parts of the island, hunting has been a major threat and is directly responsible for local extinctions (Rijksen and Meijaard 1999). Even low levels of hunting for traditional purposes strongly reduce orangutan population densities (Marshall et al. 2006). Indeed, recent vortex models showed that a 2% hunting rate is not sustainable for this species (Singleton et al. 2004, Marshall et al. in prep.). Major reasons for hunting include: bushmeat trade, wanton killing as part of poaching for other forest products (such as gaharu or aloe wood), use of body parts for traditional medicine, pet trade and to mitigate conflicts with agriculture.

6. 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. Several hundred Bornean orangutan orphans who were confiscated by local authorities have been entrusted to different orphanages in both Malaysia and Indonesia. They are in the process of being rehabilitated into the wild.

Conservation Actions [top]

Conservation Actions: The Bornean orangutan is a fully protected species in both Malaysia and Indonesia legislation. This species is listed on Appendix I of CITES.

Although some major populations are found within the network of protected areas existing in Borneo, it is now well established that the vast majority of Bornean orangutans live outside protected forests. New mechanisms to ensure their long-term survival outside protected forests are urgently needed.

Citation: Ancrenaz, M., Marshall, A., Goossens, B., van Schaik, C., Sugardjito, J., Gumal, M. & Wich, S. 2008. Pongo pygmaeus. The IUCN Red List of Threatened Species 2008: e.T17975A7640635. . Downloaded on 25 June 2016.
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