Scientists have identified a new species of orangutan in Indonesia, but there are so few individuals in the population that the newly named Tapanuli orangutan is already being described as one of the most endangered great ape species in the world.
The Tapanuli orangutan (Pongo tapanuliensis) lives in the Batang Toru forest, south of Lake Toba on the island of Sumatra.
Fewer than eight hundred of the primates remain and they are surviving in about 1,000 square kilometres of remaining habitat, which is divided into three blocks of forest, separated by roads and agricultural land. There is no great ape species that has a smaller population.
Matthew Nowak, who is the co-author of the recently published “Population
Habitat Viability Analysis for Orangutans,” says that, despite only just being described, “with so few individuals left, the Tapanuli orangutan is already the most endangered great ape species in the world.”
Serge Wich from the IUCN/SSC Primate Specialist Group’s section on great apes, said: “Orangutans reproduce extremely slowly, and if more than 1 percent of the population is lost annually this will spiral them to extinction.”
Most of the Batang Toru forest has protected status, but two potentially devastating industrial projects – a hydroelectric dam and an expansion of gold mining – are proposed in a sensitive area of connectivity inside the unprotected area.
The international team of scientists who identified the Tapanuli orangutan came to their conclusion after comparing its skeleton and genomes with the two other orangutan species, the Bornean orangutan (Pongo pygmaeus) and the Sumatran orangutan (Pongo abelii).
The researchers, whose paper has just been published in the journal Current Biology, say that the Tapanuli orangutan is genetically and morphologically distinct from the other two species. The new species, they say, is more closely related to the Bornean orangutan than the other orangutans in Sumatra, who live further north.
The oldest lineage belongs to the newly discovered species.
When the scientists compared the cranio-mandibular and dental characteristics of an orangutan who died from wounds inflicted by local villagers in November 2013 with those of 33 adult male orangutans at a similar stage of development, they found consistent differences.
The Tapanuli orangutan’s skull was found to be smaller than that of Sumatran and Bornean orangutans. Its face was flatter and its canine teeth were wider.
“Our analyses of 37 orangutan genomes provided a second line of evidence,” the researchers said.
The researchers also found some subtle differences between the call of the Tapanuli orangutan and that of other orangutan populations.
The Tapanuli orangutans have frizzier hair than their Bornean and Sumatran relatives, and the females grow beards. The dominant males have a prominent moustache and flat flanges covered in downy hair, whereas the flanges of older males are more like those of Bornean males.
Featured image © Maxime Aliaga