Tuesday last week was International Orangutan Day. This year, it followed hot on the heels of exciting genetic results from Sumatra that were made public at the International Primatological Society’s biannual conference last Sunday, which suggest the discovery of a new species of the ape.
Zurich University researcher Michael Krutzen studied the southernmost population, known as the Batang Toru orangutans, in the Tapanuli region of northern Sumatra.
“From a genetics point of view, we were taken by surprise to see these stark differences compared to other Sumatran orangutan populations further north,” he said. “Our findings highlight the urgent need for special conservation status for the Batang Toru forests.”
Illustration: Kevin Sheu
Indonesia is home to 59 primate species, of which 35 are found only in Indonesia. However, today about 70 percent of Indonesia’s primate species are threatened with extinction.
The majority of orangutans live in the protected Leuser Ecosystem, but the regional Aceh Government plans to develop the area, which is reportedly rich in minerals.
“We are extremely concerned about this situation. With these new developments, it seems crystal clear the Aceh Government deliberately intends to open up and destroy huge tracts of the Leuser Ecosystem. This will be disastrous for Sumatra’s orangutans and also Sumatra’s other iconic megafauna — the Sumatran rhino, elephant and tiger,” the Orangutan Project’s conservation director Ian Singleton said.
Orangutans have been studied for 200 years, and in 1837 were the first great ape species to be displayed at the London Zoo. Charles Darwin’s observations of Jenny, the zoo’s first captive orangutan, led him to write in The Descent of Man: “Let man visit Ouranoutang in domestication, hear its expressive whine, see its intelligence … as if it understands every word said, see its affection to those it knew, see its passion and rage, sulkiness and very actions of despair; and then let him boast of his proud pre-eminence.”
Due to their gentle nature, orangutans were Hollywood’s favorite ape. However, after years of animal cruelty — when movies such as Every Which Way But Loose were made — the genre came to an end.
Orangutan experts are pleased by motion-capture performances, such as Karin Konoval’s portrayal of Maurice in the new Planet of the Apes movies. Konoval modeled her performance on Towan, the oldest captive male orangutan in the US and a resident of Woodland Park Zoo in Seattle, Washington. Primate expert Frans de Waal said her performance was “superb.”
Today’s zoological collections of orangutans, such as that at Chester Zoo in the UK, provide breeding programs, conservation initiatives and captive groups for study.
Despite the declining populations of its subjects, field research on the Bornean (Pongo pygmaeus) and the Sumatran (Pongo abelii) orangutans still yields fascinating data. It has recently been discovered that wild orangutans can make plans for the future. Adult cheek-padded male Sumatran orangutans make a final “long call” before bed. Remarkably, these vocalizations broadcast important information across several kilometers of rainforest, including his intended direction of travel the following day, up until 4pm. Female orangutans need to be aware of this, as it allows those that are sexually receptive to seek him out, confirming that females prefer the locally dominant male (who tends not to rape).
Because flanged, or dominant, males will fight other males, sexually unreceptive females will also follow him to receive his protection from unflanged males who are likely to harass and rape unreceptive females. The study confirms that forward thinking is an adaptive trait in both sexes and not unique to humans, as previously thought.
As part of the Tuanan Orangutan Research Project, Brigitte Spillmann established that long calls can be used by listening orangutans to differentiate among males. Spillmann also found that the males’ long calls change according to the context. For example, one male might show off by noisily “snag crashing” — pushing over a dead tree — and another male will respond with a distinct long call.
Orangutans diverged from the lineage leading to humans, gorillas, chimpanzees and bonobos about 10 million years ago. They are the only Asian great ape and the only non-human ape with a fossil record. From it we know that archaic orangutans had bigger heads and far bigger teeth. The fossil record also suggests that 5 million years ago, orangutans spent more time on the ground and used more complex tools. It is thought that living in trees limits the tool use of modern orangutans.
“Orangutans are not more intelligent than chimps or bonobos in all domains, but they do have greater technical intelligence,” the University of Zurich’s Karin Isler said.
Male orangutans are three times the size of females. They also exhibit other ancestral traits of great apes, including rape, a lack of infanticide, extended lifespans (wild orangutans can live 50 years), and prolonged sexual intercourse. Orangutans and humans are more like each other than other apes in their prolonged, flexible and varied copulation postures.
Analysis of the genes for proteins in seminal fluid, associated with sperm competition in apes, has revealed that they are inactive in orangutans. This suggests that their mating system, which involves protracted mating with a single dominant male, did not alter after separating from the common ancestor of great apes. Prolonged intercourse among humans may also date back many millions of years.
It has been claimed that orangutan wrists are evolving a ball-and-socket joint, which would give them greater flexibility in the trees than they already possess and contribute to further divergence from other apes.
However, with habitat loss serving as their greatest enemy, safety may no longer be found high in the canopy. The uniquely human adaptations of long muscular legs, arched feet and Achilles tendons that enable running on the ground might help them more in the long term.
Female orangutans do not breed until 15 years of age, they have one baby at a time and six to eight years can pass before their next offspring. Combined with habitat loss, this makes the orangutan vulnerable to extinction.
At the upcoming October Convention on Biodiversity, the Sumatran orangutan is to be included in the list of the world’s top 25 most-endangered primates.
The orangutan is the only great ape with an annual international day, so stop buying palm oil products (a crop that encroaches on their habitats in Sumatra and Borneo) and consider “big upping” your endangered red-haired relative — and the new Sumatran species — while you still have the opportunity to do so.
You can virtually visit the Sumatran orangutans and the disappearing Tripa peat swamp at www.vEcotourism.org.
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