Scientists have discovered a new species of orangutan — but there are so few individuals that the new species is the rarest great ape on Earth.
Until now, we thought there were only two species of orangutan: the Sumatran and Bornean orangutans, both of which are critically endangered. The new species, called Pongo tapanuliensis, is found in the isolated Batang Toru forest in Sumatra, Indonesia. And it’s estimated that there are fewer than 800 individuals left, making it very vulnerable to extinction, according to a study published today in Current Biology.
There had been a few hints that the so-called Tapanuli orangutans were different. Previous research showed that this population of orangutans behaved differently than other orangutans and had some genetic differences. But it wasn’t clear whether those differences were enough to name a new species. For a long time, the Tapanuli orangutans were thought to belong to the species Pongo abelii, also known as the Sumatran orangutan.
But then in 2013, researchers got access to the skeleton of an orangutan found in the Tapanuli region. The orangutan, named Raya, had died after being harassed and injured by people, according to National Geographic. A comparison between Raya’s skull and teeth and those of 33 other adult male orangutans revealed that there were enough differences to grant a new species designation. The researchers also analyzed the genomes of 37 orangutans, and showed that the Tapanuli population split from the Bornean orangutans more than three million years ago. Then less than 700,000 years ago, the Bornean and Sumatran orangutans separated into two distinct species.
"The Batang Toru orangutans appear to be direct descendants of the initial orangutans that had migrated from mainland Asia, and thus constitute the oldest evolutionary line within the genus Pongo," said study co-author Alexander Nater of the University of Zurich, in a statement.
The orangutans are threatened by hunting and habitat loss. And with fewer than 800 individuals remaining, they’re at risk of going extinct. In comparison, there are an estimated 55,000 Bornean orangutans and an estimated 14,000 Sumatran orangutans in the world. Identifying the new species is the first step to ensure that the Tapanuli orangutans are adequately protected. But it also speaks about how little we still know about the world surrounding us.
"Great apes are among the best-studied species in the world," said study co-author Erik Meijaard of the Australian National University in a statement. "If after 200 years of serious biological research we can still find new species in this group, what does it tell us about all the other stuff that we are overlooking: hidden species, unknown ecological relationships, critical thresholds we shouldn't cross?"