EtymologyThe name "orangutan" (also written orang-utan, orang utan, orangutang, and ourang-outang) is derived from the words ''orang'', meaning "person", and ''hutan'', meaning "forest". The locals originally used the name to refer to actual forest-dwelling human beings, but the word underwent a semantic extension to include apes of the ''Pongo'' genus at an early stage in the history of Malay. The word ''orangutan'' appears in its older form ''urangutan'', in a variety of premodern sources in the language. The earliest of these is the , a ninth-century or early tenth-century Javanese adaption of the Sanskrit . In these Old Javanese sources, the word ''urangutan'' refers only to apes and not to forest-dwelling human beings. The word was not originally Javanese, but was borrowed from an early at least a thousand years ago. Hence the ultimate origin of the term "orangutan" as denoting the ''Pongo'' ape was most likely . The first printed attestation of the word for the apes is in Dutch physician ’ 1631 ''Historiae naturalis et medicae Indiae orientalis''. He reported that Malays had informed him the ape could talk, but preferred not to "lest he be compelled to labour". The word appeared in several German-language descriptions of Indonesian zoology in the 17th century. It has been argued that the word comes specifically from the Banjarese variety of Malay, but the age of the Old Javanese sources mentioned above make Old Malay a more likely origin for the term. Cribb and colleagues (2014) suggest that Bontius' account referred not to apes (as this description was from Java where the apes were not known from) but to humans suffering some serious medical condition (most likely ) and that his use of the word was misunderstood by , who was the first to use the term in a publication a decade later. The word was first attested in English in 1691 in the form ''orang-outang'', and variants ending with ''-ng'' are found in many languages. This spelling (and pronunciation) has remained in use in English up to the present but has come to be regarded as incorrect. The loss of "h" in ''utan'' and the shift from -ng to -n has been taken to suggest the term entered English through . In Malay, the term was first attested in 1840, not as an indigenous name but referring to how the English called the animal. The word 'orangutan' in Malay and Indonesian today was borrowed from English or Dutch in the 20th century—explaining why the initial 'h' of 'hutan' is also missing. The name of the genus, ''Pongo'', comes from a 16th-century account by , an English sailor held prisoner by the Portuguese in , which describes two anthropoid "monsters" named Pongo and Engeco. He is now believed to have been describing s, but in the 18th century, the terms orangutan and pongo were used for all . French naturalist used the term ''Pongo'' for the genus in 1799. Battel's "Pongo", in turn, is from the Kongo word ''mpongi'' or other from the region: Lumbu ''pungu'', Vili ''mpungu'', or Yombi ''yimpungu''.
Taxonomy and phylogenyThe orangutan was first described scientifically in 1758 in the '' '' of as ''Homo Sylvestris''. It was renamed ''Simia pygmaeus'' in 1760 by his student Christian Emmanuel Hopp and given the name ''Pongo'' by Lacépède in 1799. The populations on the two islands were suggested to be separate species when '' P. abelii'' was described by French naturalist in 1827. In 2001, ''P. abelii'' was confirmed as a full species based on molecular evidence published in 1996, and three distinct populations on were elevated to subspecies (''P. p. pygmaeus'', ''P. p. morio'' and ''P. p. wurmbii''). The description in 2017 of a third species, '' P. tapanuliensis'', from Sumatra south of , came with a surprising twist: it is more closely related to the Bornean species, ''P. pygmaeus'' than to its fellow Sumatran species, ''P. abelii''. The Sumatran orangutan genome was sequenced in January 2011. Following humans and s, the Sumatran orangutan became the third species of to have its genome sequenced. Subsequently, the Bornean species had its genome sequenced. was found to be lower in Bornean orangutans (''P. pygmaeus'') than in Sumatran ones (''P. abelii''), despite the fact that Borneo is home to six or seven times as many orangutans as Sumatra. The researchers hope these data may help conservationists save the endangered ape, and also prove useful in further understanding of human . Similarly to gorillas and chimpanzees, orangutans have 48 s, in contrast to humans, . According to molecular evidence, within apes (superfamily Hominoidea), the s diverged during the early between 24.1 and 19.7 million years ago (mya), and the orangutans diverged from the African great ape lineage between 19.3 and 15.7 mya. Israfil and colleagues (2011) estimated based on , , and that the Sumatran and Bornean species diverged 4.9 to 2.9 mya. By contrast, the 2011 genome study suggested that these two species diverged around 400,000 years ago, more recently than was previously thought. Also, the orangutan genome was found to have evolved much more slowly than chimpanzee and human DNA. A 2017 genome study found that the Bornean and Tapanuli orangutans diverged from Sumatran orangutans about 3.4 mya, and from each other around 2.4 mya. Orangutans travelled from Sumatra to Borneo as the islands were connected by s as parts of Sundaland during recent glacial periods when sea levels were much lower. The present range of Tapanuli orangutans is thought to be close to where ancestral orangutans first entered what is now Indonesia from mainland Asia.
Fossil recordThe three orangutan species are the only extant members of the . This subfamily also included the extinct genera '' '', which lived in southern China and Thailand 8–2 mya, '' Indopithecus'', which lived in India from 9.2 to 8.6 mya; and '' '', which lived in India and Pakistan from 12.5 mya until 8.5 mya. These s likely lived in drier and cooler environments than orangutans do today. '' piriyai'', which lived in Thailand 5–7 mya, is believed to be the closest known relative of the orangutans. The largest known primate, '' '', was also a member of Ponginae and lived in China, from 2 mya to 300,000 years ago. The oldest known record of ''Pongo'' is from the of , consisting of teeth ascribed to extinct species ''P. weidenreichi''. ''Pongo'' is found as part of the faunal complex in the Pleistocene cave assemblage in Vietnam, alongside ''Giganopithecus'', though it is known only from teeth. Some described under the name '' P. hooijeri'' have been found in Vietnam, and multiple fossil subspecies have been described from several parts of southeastern Asia. It is unclear if these belong to ''P. pygmaeus'' or ''P. abelii'' or, in fact, represent distinct species. During the Pleistocene, ''Pongo'' had a far more extensive range than at present, extending throughout and mainland Southeast Asia and South China. Teeth of orangutans are known from that date to 60,000 years ago. The range of orangutans had contracted significantly by the end of the Pleistocene, most likely because of the reduction of forest habitat during the .Though they may have survived into the Holocene in Cambodia and Vietnam.
CharacteristicsOrangutans display significant ; females typically stand tall and weigh around , while flanged adult males stand tall and weigh . Compared to humans, they have proportionally long arms, a male orangutan having an of about , and short legs. Most of their bodies are covered in coarse hair that is generally red but ranges from bright orange to or dark chocolate, while the skin is grey-black. Though largely hairless, males' faces can develop some hair, giving them a beard. Orangutans have small ears and noses; the ears are unlobed. The mean The braincase is elevated relative to the facial area, which is concave and prognathous. Compared to chimpanzees and gorillas, the which show their dominance to other males. The cheek pads are made mostly of fatty tissue and are supported by the musculature of the face. Mature males also develop large throat pouches and long Orangutan hands have four long fingers but a dramatically shorter for a strong grip on branches as they travel high in the trees. The resting configuration of the fingers is curved, creating a suspensory hook grip. With the thumb out of the way, the fingers (and hands) can grip securely around objects with a small diameter by resting the tops of the fingers against the inside of the palm, thus creating a double-locked grip. Their feet have four long toes and an opposable big toe, enabling orangutans to grasp things securely both with their hands and with their feet. Since their hip joints have the same flexibility as their shoulder and arm joints, orangutans have less restriction in the movements of their legs than humans have. Orangutans move through the trees by both vertical climbing and . Compared to other great apes, they infrequently descend to the ground where they are more cumbersome. Unlike gorillas and chimpanzees, orangutans are not true knuckle-walkers. Instead they tuck in their digits and shuffle on the sides of their hands and feet. Compared to their relatives in Borneo, Sumatran orangutans are thinner with paler and longer hair and a longer face. Tapanuli orangutans resemble Sumatran orangutans more than Bornean orangutans in body build and fur colour. They have frizzier hair, smaller heads, and have flatter and wider faces than the other two orangutan species.
Ecology and behaviourOrangutans are mainly and inhabit , particularly lowland and old . Population densities are highest in habitats near rivers, such as and , while drier forests away from the are less inhabited. Population density also decreases at higher elevations. Orangutans occasionally enter grasslands, cultivated fields, gardens, young , and shallow lakes. Most of the day is spent feeding, resting, and travelling. They start the day feeding for two to three hours in the morning. They rest during midday, then travel in the late afternoon. When evening arrives, they prepare their nests for the night. Potential predators of orangutans include s, clouded leopards and . The absence of tigers on Borneo has been suggested as a reason Bornean orangutans are found on the ground more often than their Sumatran relatives. The most frequent orangutan parasites are s of the genus '' '' and the '' Balantidium coli''. Among ''Strongyloides'', the species ''S. fuelleborni'' and ''S. stercoralis'' are commonly reported in young individuals. Orangutans also use the plant species ''Dracaena (plant), Dracaena cantleyi'' as an anti-inflammatory balm.
Diet and feedingOrangutans are primarily frugivore, fruit-eaters, and 57–80% of their feeding time is spent foraging for fruits. Even during times of scarcity, fruit can still take up 16% of feeding. Orangutans prefer fruits with soft pulp, arils or seed-walls surrounding their seeds, as well as trees with large crops. Common fig, Figs fit both preferences and are thus highly favoured, but they also consume drupes and berries. Orangutans are thought to be the sole fruit disperser for some plant species including the vine species ''Strychnos ignatii'' which contains the toxic alkaloid strychnine. Orangutans also supplement their diet with leaves, which take up 25% of their foraging time on average. Leaf eating increases when fruit gets scarcer, but even during times of fruit abundance, orangutans will eat leaves 11–20% of the time. The leaf and stem material of ''Borassodendron borneensis'' appears to be an important food source during low fruit abundance. Other food items consumed by the apes include , , bird eggs, insects and small vertebrates including the slow loris. In some areas, orangutans may practice geophagy, which involves consuming soil and other earth substances. The apes may eat tubes of soil created by termites along tree trunks as well as descend to the ground to uproot soil to eat. Orangutans are also known to visit mineral licks at the clay or sandstone-like walls of cliffs or earth depressions. Soils appear to contain a high concentration of kaolin, which counteracts toxic tannins and phenolic acids found in the orangutan's diet.
Social lifeThe social structure of the orangutan can be best described as solitary but social; they live a more solitary lifestyle than the other great apes. Bornean orangutans are generally more solitary than Sumatran orangutans. Most social bonds occur between adult females and their dependent and weaned offspring. Resident females live with their offspring in defined home ranges that overlap with those of other adult females, which may be their immediate relatives. One to several resident female home ranges are encompassed within the home range of a resident male, who is their main mating partner. Interactions between adult females range from friendly to avoidance to antagonistic. The home ranges of resident males can overlap greatly, though encounters are relatively rare and hostile. Adult males are Dominance (ethology), dominant over sub-adult males, the latter of which keep their distance. Orangutans biological dispersal, disperse and establish their home ranges by age 11. Females tend to settle close to their mothers, while males disperse much farther but may include their natal range within their new home range. They enter a transient phase, which lasts until a male can challenge and displace a dominant, resident male from his home range. Both resident and transient orangutans aggregate on large fruiting trees to feed. The fruits tend to be abundant, so competition is low and individuals may engage in social interactions. Orangutans will also form travelling groups with members moving between different food sources. They are often consortships between an adult male and a female. Social grooming is uncommon among orangutans.
CommunicationOrangutans communicate with various vocals and sounds. Males will make long calls, both to attract females and to advertise themselves to other males. These are divided into three parts; they begin with grumbles, climax with pulses and end with bubbles. Both sexes will try to intimidate conspecifics with a series of low guttural noises known collectively as the "rolling call". When annoyed, an orangutan will suck in air through pursed lips, making a kissing sound known as the "kiss squeak". Mothers produce throatscrapes to keep in contact with their offspring. Infants make soft hoots when distressed. Orangutans are also known to produce smacks or blowing a raspberry, blow raspberries when making a nest. Mother orangutans and offspring also use several different gestures and expressions such as beckoning, stomping, lower lip pushing, object shaking and "presenting" a body part. These communicate goals such as "acquire object", "climb on me", "climb on you", "climb over", "move away", "play change: decrease intensity", "resume play" and "stop that".
Reproduction and developmentMales become sexually mature at around age 15. They may exhibit Neoteny, arrested development by not developing the distinctive cheek pads, pronounced throat pouches, long fur, or long calls until a resident dominant male is absent. The transformation from unflanged to flanged can occur quickly. Flanged males attract females in oestrous with their characteristic long calls, which may also suppress development in younger males. Unflanged males wander widely in search of oestrous females and upon finding one, will Sexual coercion among animals, force copulation on her, the occurrence of which is unusually high among mammals. Females prefer to mate with the fitter flanged males and seek their company for protection. Non-ovulation, ovulating females do not usually resist copulation with unflanged males, as the chance of conception is low. Resident males may form consortships that last for days, weeks or months after copulation. Homosexual behavior in animals, Homosexual behaviour has been recorded in the context of both affiliative and aggressive interactions. Unlike females of other great ape species, orangutans do not exhibit sexual swellings to signal fertility. The average age in which a female first gives birth is 15 years and they have a six to nine year interbirth interval, the longest among the great apes. Gestation lasts around nine months and infants weigh at birth. Usually only a single infant is born; twins are a rare occurrence. Unlike many other primates, male orangutans do not seem to practice Infanticide (zoology), infanticide. This may be because they cannot ensure they will sire a female's next offspring, because she does not immediately begin ovulating again after her infant dies. There is evidence that females with offspring under six years old generally avoid adult males. Females do most of the caring of the young, while males play no role. A female often has an older offspring with her to help socialise the infant. Infant orangutans completely depend on their mothers for the first two years of their lives. The mother will carry the infant while travelling, and feed it and sleep with it in the same night nest. For the first four months, the infant is carried on its belly and almost never without physical contact. In the following months, the time an infant spends with its mother decreases. When an orangutan reaches the age of one-and-a-half years, its climbing skills improve and it will travel through the canopy holding hands with other orangutans, a behaviour known as "buddy travel". After two years of age, juvenile orangutans will begin to move away from their mothers temporarily. They reach adolescence at six or seven years of age and will socialise with their peers while still having contact with their mothers. Females may nurse their offspring for up to eight years, which is more than any mammal. Typically, orangutans live over 30 years both in the wild and in captivity.
NestingOrangutans Nest-building in primates, build nests specialised for either day or night use. These are carefully constructed; young orangutans learn from observing their mother's nest-building behaviour. In fact, nest-building ability is a leading cause for young orangutans to regularly leave their mother. From six months of age onwards, orangutans practice nest-building and gain proficiency by the time they are three years old. Construction of a night nest is done by following a sequence of steps. Initially, a suitable tree is located. Orangutans are selective about sites, though many tree species are used. The nest is then built by pulling together branches under them and joining them at a point. After the foundation has been built, the orangutan bends smaller, leafy branches onto the foundation; this serves the purpose of and is termed the "mattress". After this, orangutans stand and braid the tips of branches into the mattress. Doing this increases the stability of the nest and is the final act of nest-building. Orangutans may add features, such as "pillows", "blankets", "roofs" and "bunk-beds" to their nests.
Intelligence and cognitionOrangutans are among the most intelligent non-human primates. Experiments suggest they can Object permanence#In animals, track the displacement of objects both visible and hidden. Zoo Atlanta has a touch-screen computer on which their two Sumatran orangutans play games. A 2008 study of two orangutans at the Leipzig Zoological Garden, Leipzig Zoo showed orangutans can use "calculated reciprocity", which involves weighing the costs and benefits of gift exchanges and keeping track of these over time. Orangutans are the first nonhuman species documented to do so. In a 1997 study, two captive adult orangutans were tested with the cooperative pulling paradigm. Without any training, the orangutans succeeded in pulling off an object to get food in the first session. Over the course of 30 sessions, the apes succeeded more quickly, having learned to coordinate. An adult orangutan has been documented to pass the mirror test, indicating self-awareness. Mirror tests with a 2-year-old orangutan failed to reveal self-recognition. Studies in the wild indicate that flanged male orangutans plan their movements in advance and signal them to other individuals. Experiments have also suggested that orangutans can Displacement (linguistics), communicate about things that are not present, mother orangutans remain silent in the presence of a perceived threat but when it passes, the mother produces an alarm call to their offspring to teach them about the danger. Orangutans and other great apes show Laughter in animals, laughter-like vocalisations in response to physical contact such as wrestling, play chasing or tickling. This suggests that laughter derived from a common origin among primate species and therefore evolved before the origin of humans. Orangutans have also been found to have voluntary control over vocal fold oscillation, which is essential for speech in humans, and can learn and mimic new sounds. Bonnie (orangutan), Bonnie, an orangutan at the National Zoological Park (United States), US National Zoo, was recorded spontaneously whistling after hearing a caretaker. She appears to whistle without expecting a food reward.
Tool use and cultureTool use in orangutans was observed by primatologist in ex-captive populations. Orangutans in Suaq Balimbing were recorded to develop a tool kit for use in foraging which consisted of both insect-extraction sticks for use in the hollows of trees and seed-extraction sticks for harvesting seeds from hard-husked fruit. The orangutans adjusted their tools according to the task at hand, and preference was given to oral tool use. This preference was also found in an experimental study of captive orangutans. Orangutans have been observed to jab at catfish with sticks, so that the panicked prey would flop out of ponds and into the ape's waiting hands. Orangutan have also been documented to save tools for future use. When building a nest, orangutans appear to have some technical knowledge of construction and choose branches they know can support their body weight. Primatologist Carel van Schaik, Carel P. van Schaik and biological anthropologist Cheryl D. Knott further investigated tool use in different wild orangutan populations. They compared geographic variations in tool use related to the processing of ''Neesia'' fruit. The orangutans of Suaq Balimbing were found to be avid users of insect and seed-extraction tools when compared to other wild orangutans. The scientists suggested these differences are cultural as they do not correlate with habitat. The orangutans at Suaq Balimbing live in dense groups and are socially tolerant; this creates good conditions for social transmission. Further evidence that highly social orangutans are more likely to exhibit cultural behaviours came from a study of leaf-carrying behaviours of formerly captive orangutans that were being rehabilitated on the island of Kaja in Borneo. Wild orangutans in Tuanan, Borneo, were reported to use tools in acoustic communication. They use leaves to amplify the kiss squeak sounds they produce. The apes may employ this method of amplification to Deception in animals, deceive the listener into believing they are larger animals. In 2003, researchers from six different orangutan field sites who used the same behavioural coding scheme compared the behaviours of the animals from each site. They found each orangutan population used different tools. The evidence suggested the differences were cultural: first, the extent of the differences increased with distance, suggesting cultural diffusion was occurring, and second, the size of the orangutans' cultural repertoire increased according to the amount of social contact present within the group. Social contact facilitates cultural transmission.
PersonhoodIn June 2008, Spain became the first country in the world to recognise the rights of some non-human great apes, when its parliament's cross-party environmental committee urged the country to comply with the recommendations of the Great Ape Project, which are that chimpanzees, bonobos, orangutans, and gorillas not to be used for animal experiments. In December 2014, a court in Argentina ruled that an orangutan named Sandra at the Buenos Aires Zoo must be moved to a sanctuary in Brazil to provide her "partial or controlled freedom". Animal rights groups like Great Ape Project Argentina interpreted the ruling as applicable to all species in captivity, and legal specialists from the Argentina's Federal Chamber of Court of cassation, Criminal Cassatio considered the ruling applicable only to non-human hominids.
Orangutans and humansOrangutans were known to the native people of Sumatra and Borneo for millennia. The apes are known as ''maias'' in Sarawak and ''mawas'' in other parts of Borneo and in Sumatra. While some communities hunted them for food and decoration, others placed taboos on such practices. In central Borneo, some traditional folk beliefs consider it bad luck to look in the face of an orangutan. Some folk tales involve orangutans mating with and kidnapping humans. There are even stories of hunters being seduced by female orangutans. Europeans became aware of the existence of the orangutan in the 17th century. Explorers in Borneo hunted them extensively during the 19th century. The first scientific description of orangutans was given by Dutch anatomist Petrus Camper, who observed the animals and dissected some specimens. Camper mistakenly thought that flanged and unflanged male orangutans were different species, a misconception corrected after his death. Little was known about orangutan behaviour until the field studies of Birutė Galdikas, who became a leading authority on the apes. When she arrived in Borneo in 1971, Galdikas settled into a primitive bark-and-thatch hut at a site she dubbed Camp Leakey, in Tanjung Puting. She studied orangutans for the next four years and developed her PhD thesis for UCLA. Galdikas became an outspoken advocate for orangutans and the preservation of their rainforest habitat, which is rapidly being devastated by logging industry, loggers, plantations, gold miners, and unnatural Wildfire, forest fires. Along with Jane Goodall and Dian Fossey, Galdikas is considered to be one of Leakey's Angels, named after anthropologist Louis Leakey.
In fictionOrangutans first appeared in Western fiction in the 18th century and have been used to comment on human society. Written by the pseudonymous A. Ardra, ''Tintinnabulum naturae'' (The Bell of Nature, 1772) is told from the point of view of a human-orangutan hybrid who calls himself the "metaphysician of the woods". Over half a century later, the anonymously written work ''The Orang Outang'' is narrated by a pure orangutan in captivity in the US, writing to her friend in Java and critiquing Boston society. Thomas Love Peacock's 1817 novel ''Melincourt (novel), Melincourt'' features Sir Oran Haut Ton, an orangutan who participates in English society and becomes a candidate for Member of Parliament (United Kingdom), Member of Parliament. The novel satirises the class and political system of Britain. Oran's reliability, honesty and status as a "natural man" stand in contrast to the cowardice, greed, folly, and inequality of "civilised" human society. In Frank Challice Constable's ''The Curse of Intellect'' (1895), the protagonist Reuben Power travels to Borneo to capture and train an orangutan "to know what a beast like that might think of us". Orangutans are featured prominently in the 1963 science fiction novel ''Planet of the Apes (novel), Planet of the Apes'' by Pierre Boulle and the Planet of the Apes, media franchise derived from it. Orangutans are typically portrayed as bureaucrats like Dr. Zaius, the science minister. Orangutans are sometimes portrayed as villains, notably in the 1832 Walter Scott novel ''Count Robert of Paris'' and the 1841 Edgar Allan Poe short story ''The Murders in the Rue Morgue'' where the ape was trained to murder by his human master. Walt Disney Company, Disney's 1967 The Jungle Book (1967 film), animated musical adaptation of ''The Jungle Book'' added an orangutan named King Louie, voiced by Louis Prima, who tries to get Mowgli to teach him how to make fire. The 1986 horror film ''Link (film), Link'' features an intelligent orangutan which serves a university professor but has sinister motives, particularly with his stalking of a student assistant. Some stories have portrayed orangutans as guides to humans, such as The Librarian (Discworld), The Librarian in Terry Pratchett's fantasy novels ''Discworld'' and in Dale Smith (poet), Dale Smith's 2004 novel ''What the Orangutan Told Alice''. More comical portrayals of the orangutan include the 1996 film ''Dunston Checks In''.
In captivityBy the early 19th century, orangutans were being kept in captivity. In 1817, an orangutan joined several other animals in London's Exeter Exchange. The ape was recorded to have shunned the company of other animals, aside from a dog, and appeared to prefer the company of humans. It was occasionally taken on coach rides dressed in a smock-frock and hat and even treated with refreshments at an inn where it impressed its host with its polite behaviour. The London Zoo housed a female orangutan named Jenny (orangutan), Jenny who was dressed in human clothing and learned to drink tea. She is remembered for her meeting with Charles Darwin who compared her reactions to those of a human child. Zoos and circuses in the Western world would continue to use orangutans and other simians as sources for entertainment, training them to behave like humans at Chimpanzees' tea party, tea parties and to perform tricks. Notable orangutan "character actors" include Jacob and Rosa of the Tierpark Hagenbeck in the early 20th century and Jiggs of the San Diego Zoo in the 1930s and 1940s. Animal rights groups have urged a stop to such acts, considering them abusive. Starting in the 1960s, zoos became more concerned with education and orangutans exhibits were designed to mimic their natural environment and displayed their natural behaviours. Ken Allen, an orangutan of the San Diego Zoo, became world famous in the 1980s for multiple escapes from his enclosures. He was nicknamed "the Harry Houdini, hairy Houdini" and was the subject of a fan club, T-shirts, bumper stickers and a song titled ''The Ballad of Ken Allen''. Galdikas reported that her cook was sexually assaulted by a captive male orangutan. The ape may have suffered from a skewed species identity and forced copulation is a standard mating strategy for low-ranking male orangutans.
Status and threatsAll three species are critically endangered according to the IUCN Red List of mammals. They are legally protected from capture, harm or killing in both Malaysia and Indonesia, and are listed under CITES#Appendix I, Appendix I by CITES, which prohibits their unlicensed trade under international law. The Bornean orangutan range has become patchy, being largely Local extinction, extirpated from several parts of the island, including the southeast. The largest remaining population is found in the forest around the Sabangau River, but this environment is at risk. The Sumatran orangutan is found only in the northern part of Sumatra, most of the population inhabiting the Leuser Ecosystem. The Tapanuli orangutan is found only in the Batang Toru forest of Sumatra. Birutė Galdikas wrote that orangutans were already endangered by and when she began studying them in 1971. During the early 2000s, orangutan habitats decreased rapidly because of logging and forest fires, and Habitat fragmentation, fragmentation by roads. A major factor has been the conversion of vast areas of subtropical or tropical moist lowland forest, tropical forest to plantations in response to international demand. Hunting is also a major problem, as is the illegal . Orangutans may be killed for the trade and bones are secretly traded in souvenir shops in several cities in Indonesian Borneo. Conflicts between locals and orangutans also pose a threat. Orangutans that have lost their homes often raid agricultural areas and end up being killed by villagers. Locals may also be motivated to kill orangutans for food or because of fear and self-defense. Mother orangutans are killed so their infants can be sold as pets, and many of these infants die without the help of their mother. Since 2012, the Indonesian authorities, with the aid of the Orangutan Information Center, confiscated 114 orangutans, 39 of which were pets. Estimates between 2000 and 2003 found 7,300 Sumatran orangutans and between 45,000 and 69,000 Bornean orangutans remain in the wild. A 2016 study estimates a population of 14,613 Sumatran orangutans in the wild, doubling previous population estimates. Fewer than 800 Tapanuli orangutan are estimated to still exist, which puts the species among the most endangered of the great apes. The table below shows a breakdown of the species and subspecies and their estimated populations from this or (in the case of ''P. tapanuliensis'') a 2017 report:
Conservation centres and organisationsSeveral organisations are working for the rescue, rehabilitation and reintroduction of orangutans. The largest of these is the Borneo Orangutan Survival (BOS) Foundation, founded by conservationist Willie Smits and which operates projects such as the Nyaru Menteng Rehabilitation Program founded by conservationist Lone Drøscher Nielsen. A female orangutan was rescued from a village brothel in Kareng Pangi village, Central Kalimantan, in 2003. The orangutan was shaved and chained for sexual purposes. Since being freed, the orangutan, named Pony, has been living with the BOS. She has been re-socialised to live with other orangutans. In May 2017, the BOS rescued an albino orangutan from captivity. The rare primate was being held captive in a remote village in Kapuas Hulu, on the island of Kalimantan in Indonesian Borneo. According to volunteers at BOS, albino orangutans are extremely rare (one in ten thousand). This is the first albino orangutan the organisation has seen in 25 years of activity. Other major conservation centres in Indonesia include those at Kumai District#Tanjung Puting National Park, Tanjung Puting National Park, Sebangau National Park, Gunung Palung National Park and Bukit Baka Bukit Raya National Park in Borneo and the Gunung Leuser National Park and Bukit Lawang in Sumatra. In Malaysia, conservation areas include Semenggoh Wildlife Centre and Matang Wildlife Centre also in Sarawak, and the Sepilok Orang Utan Sanctuary in Sabah. Major conservation centres headquartered outside the orangutans' home countries include Frankfurt Zoological Society, Orangutan Foundation International, which was founded by Galdikas, and the Australian Orangutan Project. Conservation organisations such as the Orangutan Land Trust work with the palm oil industry to improve sustainability and encourages the industry to establish conservation areas for orangutans.
See also* List of individual apes * Monkey Day * Orang Pendek * ''Orangutan Island'' * Skullduggery (1970 film), ''Skullduggery'' (1970 film)