Most Western sources attribute the name "orangutan" (also written orang-utan, orang utan, orangutang, and ourang-outang) to the Malay words orang, meaning "person", and hutan, meaning "forest". The Malay used the term to indicate forest-dwelling humans; the first recorded Malay use of "orang-utan" referring to the ape identifies it as a Western term.: 12 (There is, however, some evidence to suggest that the term may have been used in regard to apes in premodern Old Malay.)
In Western sources, the first printed attestation of the word for the apes is in Dutch physician Jacobus Bontius's 1631 Historiae naturalis et medicae Indiae orientalis. He reported that Malays claimed that 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's account referred not to apes (as this description was from Java where the apes were not known to be from) but to humans suffering some serious medical condition (most likely cretinism) and that his use of the word was misunderstood by Nicolaes Tulp, who was the first to use the term in a publication a decade later.: 10–18
The Sumatran orangutan genome was sequenced in January 2011. Following humans and chimpanzees, the Sumatran orangutan became the third species of great ape whose genome was sequenced. Subsequently, the Bornean species's genome was sequenced. Bornean orangutans (P. pygmaeus) exhibit less genetic diversity than Sumatran orangutans (P. abelii), despite the latter's population being six to seven times greater. The researchers hope these genetic data may help conservationists preserve the endangered ape, as well as learn more about human genetic diseases. Similarly to gorillas and chimpanzees, orangutans have 48 diploid chromosomes, in contrast to humans, which have 46.: 30
Compared to their relatives in Borneo, Sumatran orangutans are more slender with paler and longer hair and a longer face. Tapanuli orangutans resemble Sumatran orangutans more than Bornean orangutans in body build and hair colour. They have shaggier hair, smaller skulls, and flatter faces than the other two species.
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 tigers, clouded leopards and wild dogs.: 91 The most common orangutan parasites are nematodes of the genus Strongyloides and the ciliate Balantidium coli. Among Strongyloides, the species S. fuelleborni and S. stercoralis are reported in young individuals. Orangutans also use the plant species Dracaena cantleyi as an anti-inflammatory balm. Captive animals may suffer an upper respiratory tract disease.
Orangutans also include leaves in their diet, which take up 25% of their average foraging time. Leaves are eaten more when fruit is less available, but even during times of fruit abundance, orangutans will eat leaves 11–20% of the time. They appear to depend on the leaf and stem material of Borassodendron borneensis during times of low fruit abundance. Other food items consumed by the apes include bark, honey, bird eggs, insects and small vertebrates including slow lorises.: 65–66
Orangutans communicate with various vocals and sounds. Males will make long calls, both to attract females and to advertise themselves to other males. These calls have three components; they begin with grumbles, peak with pulses and end with bubbles. Both sexes will try to intimidate conspecifics with a series of low frequency noises known collectively as the "rolling call". When uncomfortable, an orangutan will produce a "kiss squeak", which involves sucking in air through pursed lips. Mothers produce throatscrapes to keep in contact with their offspring. Infants make soft hoots when distressed. When building a nest, orangutans will produce smacks or blow raspberries. Orangutan calls display consonant- and vowel-like components and they maintain their meaning over great distances.
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".
Unflanged males wander widely in search of oestrous females and upon finding one, may force copulation on her, the occurrence of which is unusually high among mammals. Females prefer to mate with the fitter flanged males, forming pairs with them and benefiting from their protection. Non-ovulating females do not usually resist copulation with unflanged males, as the chance of conception is low. Homosexual behaviour has been recorded in the context of both affiliative and aggressive interactions.
Females do most of the caring of the young. The mother will carry the infant while travelling, suckle it and sleep with it.: 100 During its first four months, the infant is almost never without physical contact and clings to its mother's belly. In the following months, the amount of physical contact the infant has with its mother declines. 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 are able to live alone but retain some connections with their mothers.: 100 Females may nurse their offspring for up to eight years, which is more than any other mammal. Typically, orangutans live over 30 years both in the wild and in captivity.: 15
Construction of a night nest is done by following a sequence of steps. Initially, a suitable tree is located. Orangutans are choosy about sites, though nests can be found in many tree species. To establish a foundation, the ape grabs the large branches under it and bends them so they join. The orangutan then does the same to smaller, leafier branches to create a "mattress". After this, the ape stands and braids the tips of branches into the mattress. Doing this increases the stability of the nest. Orangutans make their nests more comfortable by creating "pillows", "blankets", "roofs" and "bunk-beds".
Orangutans are among the most intelligent non-human primates. Experiments suggest they can 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 Zoo showed orangutans may practise "calculated reciprocity", which involves an individual aiding another with the expectation of being paid back. Orangutans are the first nonhuman species documented to do so.
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 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-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 can learn to mimic new sounds by purposely controlling the vibrations of their vocal folds, a trait that led to speech in humans. Bonnie, an orangutan at the US National Zoo, was recorded spontaneously whistling after hearing a caretaker. She appears to whistle without expecting a food reward.
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 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.
In June 2008, Spain would become the first country to recognise the rights of some non-human great apes, based on the guidelines 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". Sandra has since been relocated to The Center for Great Apes in the United States, as it is the only accredited orangutan sanctuary in the Americas. Animal rights groups like Great Ape Project Argentina argued the ruling should apply to all species in captivity, and legal specialists from the Argentina's Federal Chamber of Criminal Cassatio considered the ruling applicable only to non-human hominids.
Orangutans 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 an orangutan in the face. Some folk tales involve orangutans mating with and kidnapping humans. There are even stories of hunters being captured by female orangutans.: 66–71
Europeans became aware of the existence of the orangutan in the 17th century.: 60 Explorers in Borneo hunted them extensively during the 19th century. In 1779, Dutch anatomist Petrus Camper, who observed the animals and dissected some specimens, gave the first scientific description of the orangutan.: 64–65 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 loggers, palm oil plantations, gold miners, and unnatural forest fires. Along with Jane Goodall and Dian Fossey, Galdikas is considered to be one of Leakey's Angels, named after anthropologist Louis Leakey.
Orangutans 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". Around 50 years later, the anonymously written work The Orang Outang is narrated by a pure orangutan in captivity in the US, writing a letter critiquing Boston society to her friend in Java.: 108–09
By the early 19th century, orangutans were being kept in captivity. In 1817, an orangutan joined several other animals in London's Exeter Exchange. He rejected the company of other animals, aside from a dog, and preferred to be with humans. He was occasionally taken on coach rides clothed in a smock-frock and hat and even given drinks at an inn where he behaved politely for the hosts.: 64–65 The London Zoo housed a female orangutan named 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 tea parties and to perform tricks. Notable orangutan "character actors" include: Jacob and Rosa of the Tierpark Hagenbeck in Hamburg, Germany, in the early 20th century; Joe Martin of Universal City Zoo in the 1910s and 1920s; and Jiggs of the San Diego Zoo in the 1930s and 1940s.: 187–89, 193–94 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 let them display their natural behaviours.: 185, 206 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 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. American animal trafficker Frank Buck claimed to have seen human mothers acting as wet nurses to orphaned orangutan babies in hopes of keeping them alive long enough to sell to a trader, which would be an instance of human–animal breastfeeding.
Estimates in the 2000s found that around 6,500 Sumatran orangutans and around 54,000 Bornean orangutans remain in the wild. A 2016 study estimates a population of 14,613 Sumatran orangutans in the wild, twice that of previous population estimates, while 2016 estimates suggest 104,700 Bornean orangutans exist in the wild. A 2018 study found that Bornean orangutans declined by 148,500 individuals from 1999 to 2015. Fewer than 800 Tapanuli orangutans are estimated to still exist, which puts the species among the most endangered of the great apes.
Several 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 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.
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