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).
Bornean orangutans (Pongo pygmaeus) currently inhabit only the island of Borneo, excluding the southeastern portion of Borneo. Fossil evidence indicates that their past distribution included much of Southeast Asia. Pongo pygmaeus was until recently considered the only orangutan species. Sumatran orangutans (Pongo abelii) are now considered a separate species.
Biogeographic Regions: oriental (Native )
Other Geographic Terms: island endemic
Bornean orangutans are sexually dimorphic. Females range from 30 to 50 kg, whereas males are from 50 to 90 kg. Head and body length is about 1.5 meters and the arms have a spread of about 2.2 meters. They have a thin, shaggy coat that is reddish brown in color. Males have large cheek pads, which are made up of deposits of subcutaneous fat bound by connective tissue. These cheek pads continue growing for much of an adult male's life. Orangutans have a high, sloping forehead and a bulging snout. They have short, weak legs, but strong hands and arms.
Range mass: 30 to 90 kg.
Average length: 1.5 m.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
Habitat and Ecology
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).
Bornean orangutans are only found in forested areas, but can be found in various types of forests, from low-level swamps to mountainous areas 1500 m in elevation. They can be found at various heights in the trees. They may move large distances to find trees bearing fruit.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: forest ; rainforest ; mountains
The diet consists mainly of fruit, especially figs. Various species of figs ripen at different times in the year, and the movement pattern of the animals can largely be explained by their following this process. Bornean orangutans will also eat other kinds of vegetation, such as leaves, bark, buds, and flowers. They will also occasionally eat mineral-rich soil, insects, and possibly eggs and small vertebrates. They drink by reaching into tree holes and lapping water from their hands.
Animal Foods: eggs; insects
Plant Foods: leaves; wood, bark, or stems; fruit; flowers
Primary Diet: herbivore (Frugivore )
Becuase they are frugivorous, these animals play some role in seed dispersal.
Ecosystem Impact: disperses seeds
Life History and Behavior
Communication and Perception
Bornean orangutans have a vocal repertoire of about 13 sounds. Within a small social group they communicate with lip smacking. They scream when scared, and males sometimes roar. They seem to grind their teeth when frustrated. Males also emit a long series of loud groans, which can be heard by a human up to 1 kilometer away. This vocalization may serve to space males apart.
In addition to vocal communication, tactile communication is used by these animals. Social grooming is an important activity in all primates. Facial expressions, gestures, and body postures are also used to communicate.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; acoustic
All of the great apes live a long time. In captivity, Bornean orangutans may reach the age of 60 years, although the lifespan in the wild is probably shorter.
Status: captivity: 60 (high) years.
Status: captivity: 59.0 years.
Status: captivity: 57.3 years.
Status: wild: 59.0 years.
Status: captivity: 58.8 years.
Status: wild: 35.0 years.
Status: captivity: 50.0 years.
Lifespan, longevity, and ageing
Bornean orangutans are polygynous. Although mainly solitary, the home ranges of males overlap those of females. On the rare occasions that the females within their home ranges are sexually receptive, dominant males will mate with them. Younger, smaller males, which are not able to maintain home ranges of their own, often wander alone through the forests. These males may also mate with females, although such copulations are generally forced, and appear to occur as the opportunity arizes, not because the female is sexually receptive or fertile.
Mating System: polygynous
Female Bornean orangutans have an estrous cycle about 30 days in length with ovulation occurring around the 15th day. This species does not have genital swelling during estrous, and females have a light menstrual flow lasting 3 or 4 days. Copulation is usually done with the male and female facing each other, each hanging by the arms from a tree branch. Gestation can take anywhere from 233 to 263 days, and typically one offspring is born, although twinning sometimes occurs. Weaning occurs around 42 months, although the timing of this may be affected by habitat quality. The interbirth interval is about 4 years, but can be much longer if conditions are poor. In females, sexual maturity is reached at 7 years of age, by which time females have attained their adult size. Males, however, continue to grow until they are 10 years old, and do not have the physical and social maturity required for successful mating until about 14 years of age.
Breeding interval: The interbirth interval is about 4 years
Breeding season: Breeding occurs throughout the year.
Range number of offspring: 1 to 2.
Range gestation period: 233 to 263 days.
Average weaning age: 42 months.
Average age at sexual or reproductive maturity (female): 7 years.
Average age at sexual or reproductive maturity (male): 10 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous
Average birth mass: 1736.5 g.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 2555 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 2555 days.
Newborn infants weigh around 1.5 kg. Babies nurse every 3 to 4 hours, and begin to take soft food from their mothers' lips at age 4 months. A young orangutan clings to its mother's abdomen by entwining its fingers in and gripping her fur until it is a year old, then it begins to ride on her back, which it may continue to do until 2.5 years of age. An infant will scream loudly if separated from its mother. The young are not weaned until they are 3 1/2 years old.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); extended period of juvenile learning
Evolution and Systematics
The teeth of great apes help them survive times of food scarcity because they are diverse in type and material characteristics, allowing consumption of fallback foods.
"Lucas and colleagues recently proposed a model based on fracture and deformation concepts to describe how mammalian tooth enamel may be adapted to the mechanical demands of diet (Lucas et al.: Bioessays 30 2008 374-385). Here we review the applicability of that model by examining existing data on the food mechanical properties and enamel morphology of great apes (Pan, Pongo, and Gorilla). Particular attention is paid to whether the consumption of fallback foods is likely to play a key role in influencing great ape enamel morphology. Our results suggest that this is indeed the case. We also consider the implications of this conclusion on the evolution of the dentition of extinct hominins." (Constantino et al. 2009:653)
Learn more about this functional adaptation.
- Constantino PJ; Lucas PW; Lee JJ; Lawn BR. 2009. The influence of fallback foods on great ape tooth enamel. Am J Phys Anthropol. 140(4): 653-60.
- 2009. Among apes, teeth are made for the toughest times. EurekAlert! [Internet],
Molecular Biology and Genetics
Barcode data: Pongo pygmaeus
There are 2 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
-- end --
Download FASTA File
Statistics of barcoding coverage: Pongo pygmaeus
Public Records: 3
Specimens with Barcodes: 14
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1994Endangered(Groombridge 1994)
- 1990Endangered(IUCN 1990)
- 1988Endangered(IUCN Conservation Monitoring Centre 1988)
- 1986Endangered(IUCN Conservation Monitoring Centre 1986)
Bornean orangutans populations have been declining in both range and numbers for many years. The species is now in danger of becoming extinct. Humans have a long history of hunting this particular primate for various reasons, more recently for exhibition in zoos. It is estimated that at least 3 orangutans die for each one that is successfully captured and transported. They are now protected by law, but poaching still occurs. The population is currently being further devastated by the destruction of their habitat through deforestation, mainly for logging purposes.
US Federal List: endangered
CITES: appendix i
IUCN Red List of Threatened Species: endangered
Date Listed: 06/02/1970
Lead Region: Foreign (Region 10)
Population location: entire
Listing status: E
For most current information and documents related to the conservation status and management of Pongo pygmaeus , see its USFWS Species Profile
Follow link below for Tables 1a, b and c: population size estimates for P. p. wurmbii, P. p. pygmaeus and P. p. morio.
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.
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.
Relevance to Humans and Ecosystems
Economic Importance for Humans: Negative
Bornean orangutans prefer many of the same types of fruit that people do, but their numbers are so small now that this is normally not a significant problem for human food production. Attacks on humans occasionally occur.
Negative Impacts: injures humans (bites or stings)
Economic Importance for Humans: Positive
Bornean orangutans provide increasing economic benefits on Borneo by attracting "eco-tourism."
Positive Impacts: ecotourism
The Bornean orangutan, Pongo pygmaeus, is a species of orangutan native to the island of Borneo. Together with the Sumatran orangutan, it belongs to the only genus of great apes native to Asia. Like the other great apes, orangutans are highly intelligent, displaying advanced tool use and distinct cultural patterns in the wild. Orangutans share approximately 97% of their DNA with humans.
The Bornean orangutan is an endangered species, with deforestation, palm oil plantations and hunting posing a serious threat to its continued existence.
The Bornean orangutan and the Sumatran orangutan diverged about 400,000 years ago, with a continued low level of gene flow between them since then. The two orangutan species were considered merely subspecies until 1996; they were elevated to species following sequencing of their mitochondrial DNA.
- Northwest Bornean orangutan P. p. pygmaeus – Sarawak (Malaysia) & northern West Kalimantan (Indonesia)
- Central Bornean orangutan P. p. wurmbii – Southern West Kalimantan & Central Kalimantan (Indonesia)
- Northeast Bornean orangutan P. p. morio – East Kalimantan (Indonesia) & Sabah (Malaysia)
There is some uncertainty about this, however. The population currently listed as P. p. wurmbii may be closer to the Sumatran orangutan (P. abelii) than to the Bornean orangutan. If this is confirmed, P. abelii would be a subspecies of P. wurmbii (Tiedeman, 1808). In addition, the type locality of P. pygmaeus has not been established beyond doubt; it may be from the population currently listed as P. wurmbii (in which case P. wurmbii would be a junior synonym of P. pygmaeus, while one of the names currently considered a junior synonym of P. pygmaeus would take precedence for the taxon in Sarawak and northern West Kalimantan). Bradon-Jones et al considered P. morio to be a synonym of P. pygmaeus, and the population found in East Kalimantan and Sabah to be a potentially unnamed separate taxon.
Physical description 
The Bornean orangutan is the third-heaviest living primate after the two species of gorilla, and the largest truly arboreal (or tree-dwelling) animal alive today. Body weights broadly overlap with the considerably taller Homo sapiens, but that species, of course, is more variable in size. The Sumatran orangutan is similar in size, but is on average marginally lighter in weight. A survey of wild orangutans found that males weigh on average 75 kg (170 lb), ranging from 50–100 kg (110–220 lb), and 1.2–1.4 m (3.9–4.6 ft) long; females average 38.5 kg (85 lb), ranging from 30–50 kg (66–110 lb), and 1–1.2 m (3.3–3.9 ft) long. While in captivity, orangutans can grow considerably overweight, up to more than 165 kg (360 lb). The heaviest known male orangutan in captivity was an obese male named "Andy", who weighed 204 kg (450 lb) in 1959 when he was 13 years old.
The Bornean orangutan has a distinctive body shape with very long arms that may reach up to 1,5 metres in length. It has a coarse, shaggy, reddish coat and prehensile, grasping hands and feet.
Habitat and distribution 
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 (4,900 ft) above sea level. This species lives throughout the canopy of primary and secondary forests, and moves large distances to find trees bearing fruit.
It can be found in the two Malaysian states of Sabah and Sarawak, and three of the four Indonesian Provinces of Kalimantan. Due to habitat destruction, the species distribution is now highly patchy throughout the island; the species has become rare in the southeast of the island, as well as in the forests between the Rejang River in central Sarawak and the Padas River in western Sabah.
Behavior and ecology 
In history, orangutans ranged throughout Southeast Asia and into southern China, as well as on the island of Java and in southern Sumatra. They primarily inhabit peat swamp forests, tropical health forests, and mixed dipterocarp forests.
Bornean orangutan are more solitary than their Sumatran relatives. Two or three orangutans with overlapping territories may interact, but only for short periods of time. Although orangutans are not territorial, adult males will display threatening behaviors upon meeting other males, and only socialize with females to mate. Males are considered the most solitary of the orangutans. The Bornean orangutan has a lifespan of 35–45 years in the wild; in captivity it can live to be about 60.
Despite being arboreal, the Bornean orangutan travels on the ground more than its Sumatran counterpart. This may be in part because no large terrestrial predators could threaten an orangutan in Borneo. In Sumatra, orangutans must face predation by the fierce Sumatran tiger.
The Bornean orangutan diet is composed of over 400 types of food, including wild figs, durians, leaves, seeds, bird eggs, flowers, honey, insects, and, to a lesser extent than the Sumatran orangutan, bark. They have also been known to consume the inner shoots of plants and vines. They get the necessary quantities of water from both fruit and from tree holes.
Bornean orangutans have been sighted using spears to catch fish. The species has been observed using tools such as leaves to wipe off faeces, a pad of leaves for holding spiny durian fruit, a leafy branch for a bee swatter, a bunch of leafy branches held together as an "umbrella" while traveling in the rain, a single stick as backscratcher, and a branch or tree trunk as a missile. And in other regions, orangutans occasionally eat soil to get minerals that may neutralize the toxins and acids they consume in their primarily vegetarian diets. On rare occasions, orangutans will prey upon other, smaller primates, such as slow lorises.
Males and females generally come together only to mate. Subadult males (unflanged) will try to mate with any female and will be successful around half the time. Dominant flanged males will call and advertise their position to receptive females, who prefer mating with flanged males. Adult males will often target females with weaned infants as mating partners because the female is likely to be fertile.
Females reach sexual maturity and experience their first ovulatory cycle between about six and 11 years of age, although females with more body fat may experience this at an earlier age. The estrous cycle lasts between 22 and 30 days and menopause has been reported in captive orangutans at about age 48. Females tend to give birth at about 14–15 years of age. Newborn orangutans nurse every three to four hours, and begin to take soft food from their mothers' lips by four months. During the first year of its life, the young clings to its mother's abdomen by entwining its fingers in and gripping her fur. Offspring are weaned at about four years, but this could be much longer, and soon after they start their adolescent stage of exploring, but always within sight of their mother. During this period, they will also actively seek other young orangutans to play with and travel with.
A 2011 study on female orangutans in free-ranging rehabilitation programs found that individuals that were supplemented with food resources had shorter interbirth intervals, as well as a reduced age, at first birth.
Conservation status 
The Bornean orangutan is more common than the Sumatran, with about 54,500 individuals in the wild, whereas only about 6,600 Sumatran orangutans are left in the wild. Orangutan are becoming increasingly endangered due to habitat destruction and the bushmeat trade, and young orangutans are captured to be sold as pets, usually entailing the killing of their mothers.
The Bornean orangutan is endangered according to the IUCN Red List of mammals, and is listed on Appendix I of CITES. 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 20th century), and this sharp decline has occurred mostly over the past few decades due to human activities and development. Species distribution is now highly patchy throughout Borneo; it is apparently absent or uncommon in the southeast 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). A population of around 6,900 is found in Sabangau National Park, but this environment is at risk. According to an anthropologist at Harvard University, in 10 to 20 years, orangutans are expected to be extinct in the wild if no serious effort is made to overcome the threats they are facing.
This view is also supported by the United Nations Environment Programme, which stated in its 2007 report that due to illegal logging, fire and the extensive development of oil palm plantations, orangutans are endangered, and if the current trend continues, they will become extinct.
A November 2011 survey, based on interviews with 6,983 respondents in 687 villages across Kalimantan in 2008 to 2009, gave estimated orangutan killing rates of between 750 and 1800 in the year leading up to April 2008. These killing rates were higher than previously thought and confirm that the continued existence of the orangutan in Kalimantan is under serious threat. The survey did not quantify the additional threat to the species due to habitat loss from deforestation and expanding palm-oil plantations. The survey found that 73% of respondents knew orangutans were protected by Indonesian law.
However, the Indonesian government rarely prosecutes or punishes perpetrators. In a rare prosecution in November 2011, two men were arrested for killing at least 20 orangutans and a number of long-nosed proboscis monkeys. They were ordered to conduct the killings by the supervisor of a palm oil plantantion, to protect the crop, with a payment of $100 for a dead orangutan and $22 for a monkey.
Rescue and rehabilitation centers 
A number of orangutan rescue and rehabilitation projects operate in Borneo.
The Borneo Orangutan Survival Foundation (BOS) founded by Dr Willie Smits has rescue and rehabilitation centres at Wanariset and Samboja Lestari in East Kalimantan and Nyaru Menteng, in Central Kalimantan founded and managed by Lone Drøscher Nielsen. BOS also works to conserve and recreate the fast-disappearing rainforest habitat of the orangutan, at Samboja Lestari and Mawas.
Orangutan Foundation International, founded by Dr Birutė Galdikas, rescues and rehabilitates orangutans, preparing them for release back into protected areas of the Indonesian rain forest. In addition, it promotes the preservation of the rain forest for them.
See also 
This article incorporates text from the ARKive fact-file "Bornean orangutan" under the Creative Commons Attribution-ShareAlike 3.0 Unported License and the GFDL.
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