Newly discovered Sumatra orangutan species is already endangered

November 6, 2017, 8:51 a.m.
Frontal view of a male Pongo tapanuliensis orangutan.
Photo: Tim Laman/Morphobank

The first new species of orangutan in 80 years has been discovered in the rugged highland forests of Batang Toru in western Sumatra, and it's already facing habitat dangers.

Tapanuli orangutans (Pongo tapanuliensis) were first reported in the 1930s as an isolated population, but it wasn't until 2013 that scientists were able to confirm that the apes were in fact a different species from the other two extant orangutan species, the Bornean (Pongo pygmaeus) and Sumatran (Pongo abelii) orangutans.

Much of the identification work relied on field observations and a single specimen killed by villagers in the area. The Tapanuli orangutans have smaller heads and flatter faces than their counterparts, and they have frizzier hair as well. The DNA provided by the recovered specimen locked in the new species' designation for researchers.

What surprised researchers about the Tapanuli's DNA was that it had more in common with Bornean orangutans than with Sumatran orangutans, even though the latter shares the same island with the Tapanuli, albeit in the far north.

The Tapanuli are likely the closest descendants of the apes that crossed into what is now Sumatra from Asia 8 million years ago. The Sumatran apes split off from this group about 3.4 million years ago, based on genetic data, but the Bornean group may have only split from the Tapanuli's ancestors some 674,000 years ago. They continued to occasionally interbreed, and this would explain their genetic similarities.

Numbering around 800, the Tapanuli orangutans face an uncertain future. While they reside on land protected by the Indonesia government, a proposed hydroelectric dam along a Batang Toru river would flood part of their habitat and split an already small and inbred population. The dam could likely bring more humans to the area, increasing the odds of hunting.