Tapanuli: A Third Orangutan Species Exists

The Tapanuli orangutan. Image credit Tim Laman

Found living in the forests of North Sumatra in Indonesia, the Tapanuli orangutan (Pongo tapanuliensis) was originally considered to be part of the Sumatran orangutan population, but the discovery of a separate species means it is considered the most endangered of all great ape species.

Found in the Batang Toru ecosystem in the highland forests in three districts of Tapanuli, North Sumatra, this attractive animals are rare and even more endangered than African mountain gorillas.

An worldwide team of researchers from 34 institutions, led by anthropologist Alexander Nater of the University of Zurich in Switzerland, pursued two lines of evidence to determine if the ape colony was different enough from the two already acknowledged orangutan species - known as the Bornean and Sumatran - to be defined as a third. This is the first great ape species to be described by scientists in almost 90 years.

The Tapanuli orangutan bears a close resemblance to its Bornean and Sumatran cousins, but close observers may notice that it has a smaller head, slightly frizzier cinnamon-colored fur, and a "prominent moustache", the scientists wrote. The results confirmed their observations, with another surprising revelation: not only did they uncover three very old evolutionary lineages, but the newly discovered population was the oldest.

"The Batang Toru orang-utans appear to be direct descendants of the initial orang-utans that had migrated from mainland Asia, and thus constitute the oldest evolutionary line within the genus Pongo", Alexander Nater, of the University of Zurich said.

She also said she hoped it would spark new scientific debate on whether the three subspecies of the Bornean orangutan should themselves be elevated to full species of great ape, in particular the orangutan of eastern Borneo. Sumatran and Bornean orangutans separated around 674,000 years ago, the team estimates.

There are only believed to be around 800 Tapanuli orangutans left.

Erik Meijaard of the Australian National University said: "Great apes are among the best-studied species in the world. Humans are conducting a vast global experiment, but we have near-zero understanding of what impacts this really has, and how it could ultimately undermine our own survival".

In addition, the new species is also threatened with extinction due to widespread hunting in Batang Toru.

Prof Michael Krützen from the University of Zurich, Switzerland, who is one of the lead researchers of the study told BBC News.

"If steps are not taken quickly to reduce current and future threats and to conserve every last remaining bit of forest, a great ape species may become extinct within a few decades", Nowak added. "All conservation efforts must focus on protecting the species' environment".

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