Sumatran Orangutan Population More Than Double Previous Estimate

There are more than twice as many Sumatran orangutans living in the wild than previous estimates suggested, a rare bit of good news for the critically endangered species. Phil Noble/REUTERS

After a detailed survey, experts now estimate there are 14,600 Sumatran orangutans living in the wild—8,000 more than previously thought.

"Given that most news about this species and their situation tend to be negative, this is very good news," says Hjalmar Kühl, a researcher at Germany's Max Planck Institute for Evolutionary Anthropology.

The new estimate, described in a study published March 4 in the journal Science Advances, is the result of a detailed survey conducted by Kühl and his colleagues, in which they counted nests of the great apes along a vast transect in northern Sumatra, where the animals live.

Despite the good news, Sumatran orangutans (Pongo abelii, one of two orangutan species, the other being P. pygmaeus) remain critically endangered. They are threatened primarily by conversion of their forest habitat into oil palm plantations, as well as by logging and fragmentation of habitat by roads. While a large chunk of their habitat is found within Sumatra's protected Gunung Leuser National Park, the majority is outside the park and may fall victim to development if more protections aren't put in place, Kühl says. Over the past 75 years, Sumatran orangutan populations have declined by more than 80 percent.

"If enough suitable habitat can be protected and is not fragmented by...infrastructure or land conversion, orangutans have a chance of surviving," Kühl notes.

The study calculates that as many as 4,500 orangtuans could vanish by 2030 if current logging and development trends continue.