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Tuesday is International Orangutan Day. This year it follows hot on the heels of exciting genetic results from Sumatra made public at the International Primatological Society’s biannual conference on Sunday which suggest the discovery of a new species of the ape.
Dr Michael Krützen of Zurich University studied the most southern 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.”
Indonesia is home to 59 species of primate and 35 of these are found only in Indonesia. But today around 70% of Indonesia’s primate species are threatened with extinction. The majority of orangutans live in the protected Leuser Ecosystem but the local Aceh government plans to develop the area, which is reportedly rich in minerals.
Dr Ian Singleton, conservation director of the Orangutan Project, said: “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.”
Orangutans have been studied for two hundred years and in 1837 were the first great ape species to be displayed at 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 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 favourite ape. But after years of animal cruelty, during which movies such as Every Which Way But Loose were made, the genre thankfully came to an end. Orangutan experts are pleased by motion-capture performances, such as Karin Konoval’s portrayal of Maurice the new Planet of the Apes movies. Konoval modelled her performance on Towan, the oldest captive male orangutan in the US and a resident of Woodland Park Zoo. 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 programmes, conservation initiatives and captive groups for study.
Despite their declining population, field research on the Bornean (Pongo pygmaeus) and the Sumatran (Pongo abelii) orangutans still yield fascinating data. It has recently been discovered that wild orangutans can make plans for the future. Adult cheek-padded Sumatran males make a final “long call”, before bed. Remarkably, these vocalisations broadcast important information across several kilometres of rainforest, including his intended direction of travel the following day, up until 4pm in the afternoon. Females need to be aware of this this as it allows those sexually receptive to seek him out, confirming females prefer the locally dominant male (who tends not to rape).
Because flanged (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 adaptive in both sexes and not unique to humans, as previously thought.
As part of the Tuanan Orangutan Research Project, Dr Brigitte Spillmann established that long calls can be used by listening orangutans to differentiate between 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, chimps and bonobos 10m 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 5m 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,” said Karin Isler of the University of Zurich.
Orangutans males are three times the size of females. They also exhibit other ancestral great ape traits, including rape, a lack of infanticide, extended lifespan (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, have revealed that they are inactive in orangutans. This suggests that their mating system (involving protracted mating with a single dominant male) did not alter after separating from the great ape common ancestor. Humans’ prolonged intercourse may also date back many millions of years.
It has been claimed that orangutan wrists are evolving a ball and socket joint, which will give them greater flexibility in the trees than they already possess and contribute to further divergence from other apes. But with habitat loss 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 – enabling 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 October 2014 Convention on Biodiversity the Sumatran orangutan will 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 on Tuesday tweet your positivity, stop buying palm oil products (a crop that encroaches on their habitats in Sumatra and Borneo) and spend the day bigging up 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. Click ‘Take a tour’
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