A remote group of frizzy-haired orangutans on the Indonesian island of Sumatra seems to be a new species of great apes, scientists say.
But the species may not be around much longer. Its numbers are so small, and its habitat so fragmented, that it is in danger of going extinct, say the scientists who studied it.
A study published last week in the journal Current Biology said there are no more than 800 of the primates, which researchers named Pongo tapanuliensis, making it the most endangered great ape species.
The researchers say the population is highly vulnerable and its habitat is facing further pressure from development.
"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," they said.
It's the first species of great ape to be discovered by scientists in nearly 90 years. Up until now, science has recognized six great ape species: Sumatran and Bornean orangutans, eastern and western gorillas, chimpanzees, and bonobos. Some scientists also classify humans as great apes, but others argue for a separate categorization.
The research is based on analysis of the skeleton of an adult male killed in a conflict with villagers, a study of the orangutans' genes, and analysis since 2006 of behavioral and habitat differences.
The primates live in about 425 square miles in the Batang Toru forest in Northern Sumatra. They differ physically from other orangutans because of their frizzier hair and smaller heads. Their diet and habitat, along with the male's long-distance calls, also make them unique.
Russell Mittermeier, head of the primate specialist group at the International Union for Conservation of Nature, called the finding a "remarkable discovery" that puts pressure on the Indonesian government to keep the species alive.
Matthew Nowak, one of the study's authors, said the Tapanuli orangutans live in three pockets of forest that are separated by nonprotected areas.
"For the species to [survive] into the future, those three fragments need to be reconnected via forest corridors," he said.
The authors are also recommending that development plans for the region be stopped by the government.
"It is imperative that all remaining forest be protected and that a local management body works to ensure the protection of the Batang Toru ecosystem," Novak said.
The head of conservation of natural resources and ecosystems at Indonesia's Forestry and Environment Ministry, who goes by one name, Wiratno, told a news conference in Jakarta that most of Batang Toru forest became protected in December 2015.
"We are deeply committed to maintaining the survival of this species," Wiratno said.
The Batang Toru orangutan population was found during a field survey by researcher Erik Meijaard in 1997, and a research station was established in the area in 2006.
It was not until 2013, when the adult male skeleton became available, that scientists realized how different the population was.