Scientists identify new species of great ape, Pongo tapanuliensis or Tapanuli orangutan, but fear its survival is already in doubt as habitat under threat

A new species of great ape has been discovered, according to scientists studying a small population of orangutans in northern Sumatra.

Among the great apes – a group that also includes humans, gorillas, chimpanzees and bonobos – orangutans are our most distant relative. Since 2001, two distinct species have been recognised: the Bornean (Pongo pygmaeus) and Sumatran (Pongo abelii) orangutans. Now, it seems, there is a third.

“It is incredibly exciting to describe a new species of ape,” said Serge Wich, professor in primate biology at Liverpool John Moores University and a co-author of the research. Wich also noted that it was a shock to find such a distinct population given Sumatran orangutans are found just 100km away.



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But how long the new species will survive is a moot point: fewer than 800 individuals are thought to exist across a 1,000km2 area, making it the great ape species with the lowest head-count, with threats including illegal trade and habitat loss.

“It is worrying that this species is under so much threat – we have hunting in the area, there is a gold mine [and] there is a hydroelectric plant planned in an area where we find a very high density of the new species,” said Wich.



The new species has been dubbed the Tapanuli orangutan, or Pongo tapanuliensis, after the area spanned by the Batang Toru ecosystem south of Lake Toba in northern Sumatra, where the creatures live.

While it had been reported in the late 1930s that there were orangutans in the area, it wasn’t until 1997 that scientists rediscovered the population and later began studying the animals.

“I was surprised about the extent to which the Tapanuli orangutans differed genetically, morphologically as well as behaviourally from the Sumatran and Bornean orangutans,” said Dr Marina Davila-Ross, another co-author of the study, from the University of Portsmouth.

Writing in the journal Current Biology, an international team of researchers describe multiple characteristics they say indicate the Tapanuli orangutans are a distinct species.

Among the evidence, the team report how they seized the opportunity to examine the remains of an adult male Tapanuli orangutan after it was killed by villagers in November 2013.

The team compared the skull and jaws to those of 33 other adult male orangutans, held in the collections of 10 institutions around the world, revealing differences in numerous metrics – including that the skull of the Tapanuli male is smaller than that of individuals of the other two species.

The authors also looked at the characteristics of living individuals, noting that the long booming calls of the Tapanuli males differ from those of the two other known species and that the creatures have more cinnamon-coloured pelts than Bornean orangutans, with a frizzier texture – particularly when compared to the loose locks of Sumatran orangutans. The team also made note of the facial hair of the Tapanuli orangutans, pointing out that dominant males have prominent moustaches, and the females sport beards.

Facebook Twitter Pinterest The Tapanuli orangutans having more cinnamon-coloured hair than Bornean orangutans, with a far frizzier texture than that of Sumatran orangutans. Photograph: Andrew Walmsley/Sumatra Orangutan Conservation Programme/Body Shop

The researchers also carried out an analysis of the entire genomes of 37 orangutans from across Borneo and Sumatra, allowing them to unpick the animals’ evolutionary “family tree”.



The results suggest that orangutans north of Lake Toba branched off about 3.4m years ago from the more southerly population of ancestral orangutans that first arrived from mainland Asia, giving rise to the Sumatran species. A further split from the population south of Lake Toba occurred about 674,000 years ago, giving rise to the Bornean orangutans as well as the newly discovered species that, like its ancestors, live south of Lake Toba.

“The new species represents the most ancestral line of living orangutans,” said Wich.

The revelations, the team add, have also solved a mystery.

Previous research had found that a type of DNA which is passed down only by mothers, known as mitochondrial DNA, is more similar between Bornean and Tapanuli orangutans, but nuclear DNA – which includes genes from both parents – is more similar between Sumatran and Tapanuli orangutans.

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The new study reveals that even after the split between orangutans north and south of Lake Toba, the animals continued to interbreed – likely a result of roving males – resulting in mixing of the nuclear DNA. This was curtailed about 100,000 years ago – a date close to the supervolcanic eruption at Lake Toba – and stopped altogether between 20,000 and 10,000 years ago. Crucially, since the females stayed put, so too did the mitochondrial DNA.

William Amos, professor of evolutionary genetics at the University of Cambridge who was not involved in the study, said it was difficult to be exact when it came to the timings of splits in the evolutionary family tree, but that the evidence for a new species stacked up. “I’m entirely happy that this is at a level where we would recognise [the Tapanuli orangutans] as a different species or at least a subspecies,” he said. “This is clearly a really different population.”

Dr Andrew Marshallof University of York, said that the study highlighted the importance of conservation, and added that there might even be further species of great ape to be discovered.

But Professor Volker Sommer from University College London was less bowled over, pointing out that there is no clear criteria for what constitutes a new species. “Any bunch of expertised biologists can invent a new species, if they get their arguments together,” he said.

