An international team of researchers has identified a new species of orangutan living on the Indonesian island of Sumatra. Named the Tapanuli orangutan (Pongo tapanuliensis), the species is already at a high risk of extinction, with an estimated 800 individuals living in the upland forest regions of the island.
The Tapanuli orangutan (Pongo tapanuliensis). Image credit: Andrew Walmsley.
Scientists had thought that there were two orangutan species: the Sumatran orangutan (Pongo abelii) and the Bornean orangutan (Pongo pygmaeus).
However, the physical and genetic data now show that an isolated population of orangutans in Batang Toru, a region within the three Tapanuli districts in the province of North Sumatra, represents a distinct species.
“The first indications of the uniqueness of the Tapanuli population came from the skeletal material of an adult male orangutan killed in 2013 — when compared to other skulls it turned out that certain characteristics of the teeth and skull of the Tapanuli orangutan were unique,” said team member Matt Nowak of Sumatran Orangutan Conservation Programme and colleagues.
“We were quite surprised that the skull was quite different in some characteristics from anything we had seen before.”
This map shows the distribution of the Tapanuli orangutan and other orangutan species. Image credit: University of Zurich.
“When we realized that the Tapanuli orangutans were morphologically different from all other orangutans, the pieces of the puzzle fell into place,” added team member Professor Michael Krützen, from the University of Zurich.
“It is very exciting to discover a new great ape species in the 21st century,” he added.
“We identified three very old evolutionary lineages among all orangutans, despite only having two species currently described,” said team member Dr. Maja Mattle-Greminger, also from the University of Zurich.
The researchers also reconstructed the history of the Tapanuli population.
Their calculations show that the population appears to have been isolated from all other Sumatran populations for at least 10,000 to 20,000 years.
“The oldest evolutionary line in the genus Pongo is actually found in Tapanuli orangutans, which appear to be direct descendants of the first Sumatran population in the Sunda archipelago,” said team member Dr. Alexander Nater, also from the University of Zurich.
The Tapanuli orangutan is described in a paper that was published today in the journal Current Biology.
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Alexander Nater et al. Morphometric, behavioral, and genomic evidence for a new orangutan species. Current Biology, published online November 2, 2017; doi: 10.1016/j.cub.2017.09.047
