An international team of researchers has just described a new great ape species, the Tapanuli orangutan (Pongo tapanuliensis). With no more than 800 individuals, it is endemic to the three Tapanuli districts of North Sumatra, Indonesia, and occurs in roughly 1.100 km2 of upland forest in the Batang Toru Ecosystem. It is therefore the most endangered great ape species. Jaume Bertranpetit, Marc de Manuel and Tomàs Marquès-Bonet, researchers of IBE, have been involved in the study. Current Biology has published the results of the study.

Despite nearly 50 years of orangutan research in Sumatra, the Batang Toru population was only rediscovered in 1997 during a series of field surveys. It was not until 2013, however, when skeletal material from an adult male orangutan became available that the researchers realised its skull was quite different in some characteristics from orangutan skulls that they had seen before. While this suggested that the Batang Toru population was potentially unique, much stronger evidence was required to actually determine whether the Batang Toru orangutans were indeed a different species. This was achieved by studying this orangutan’s genome, together with the genome of other 36 wild orangutans, this being the largest genomic study of wild orangutans carried out to date. These data were generated at the CNAG-CRG, in Barcelona.

“After nearly ten years observing the population genetics of the great apes, it is always surprising to find new unique and isolated populations”, says Tomàs Marquès-Bonet, ICREA researcher at the Institute of Evolutionary Biology (CSIC-UPF).

This work “has enabled the identification of three very ancient evolutionary lineages”, states Marc de Manuel, researcher of the IBE. “When we realised that Batang Toru orangutans are morphologically different from all other orangutans, the pieces of the puzzle fell into place”, as Michael Krützen from the University of Zurich and responsible for the study puts it. “The oldest evolutionary line in the genus Pongo is actually found in Batang Toru orangutans, which appear to be direct descendants of the first Sumatran population in the Sunda archipelago”, he adds.

The research reveals that the Batang Toru population appears to have been isolated from all other Sumatran populations for at least 10,000 to 20,000 years. Adding additional evidence based on behavioural observations and ecological surveys from Batang Toru and other sites provided further support for the morphological and genetic findings.

With only 800 individuals alive, Tapanuli orangutans are therefore the most endangered ape species. Conservationists have drawn attention to the fact that urgent action is required to carefully review current proposals for further developments in the area that would threaten the livelihood of the new species. There is strong anthropogenic pressure on the Tapanuli orangutan due to conversion of pristine forest for mining, plans to build a hydroelectric dam, hunting, and general human encroachment. The scientists point out: “if steps are not taken quickly to reduce current and future threats to conserve every last remaining bit of forest, we may see the discovery and extinction of a great ape species within our lifetime”.

Paper: Nater, A. et al (2017). Morphometric, behavioral, and genomic evidence for a new orangutan species. Current Biology. DOI:10.1016/j.cub.2017.09.047

Photo credit: Maxime Aliaga, (SOCP)