8,000 more Sumatran orangutans than we thought, but worries remain

Finally some good news for the Sumatran orangutan population. Well, kind of.

The Sumatran orangutans’ total population was previously estimated at 6,600 individuals. But in a new study published Friday in the journal Science Advances a team of 12 scientists from the UK, the Netherlands, Indonesia, the US and Germany disagree with this figure – they say a population of 14,613 exist as of 2015.

And while this is good news, it’s not time to celebrate yet. Sumatran oranguatan populations have not increased, but rather been previously miscalculated. 

In their recent study, the study’s authors surveyed habitats previously overlooked as orangutan habitats. Individuals were found at 1,500 meters above sea level, in previously logged areas and west of the Tobas Lake: three habitats that past studies had not previously evaluated. 

“These are really remote areas,” the study’s lead author, Serge Wich from Liverpool John Moores University, tells The Christian Science Monitor in a Skype interview Sunday. “We never had the funding to survey these areas so extensively, and we just didn’t think they occurred there. Sometimes its just a week’s walk to reach [these habitats].” 

The authors say the animals’ range is now about 2.56 times as big as previously thought. And Dr. Wich says orangutans have probably always lived in these places, unbeknownst to researchers. Deforestation has not forced the animals into these areas, but it has likely made these habitats more populated.  

“They start using the parts of their home range that has not been deforested, so there will be an increase in density,” explains Wich. Deforestation typically occurs on the lowlands, but that doesn’t mean these highland individuals are safe. Regardless of where their nests are located, all Sumatran orangutans have come down to the deforested lowlands for food. 

Earlier estimates pair the smaller population figures with a 80 percent population drop in the last 75 years: a rate that Wich says it pretty much still accurate. Because finding more orangutans that exist, also means we also find more organutans that have died from human-induced causes.

“If we project orangutan losses due to deforestation [with the new population numbers] there is not difference there,” Wich tells The Monitor. “They were always probably more widespread than we thought. And some of those areas that we hadn’t gone to, they probably had orangutans that are now gone.” 

“It is therefore very important that these results are not interpreted as indicating that Sumatran orangutan numbers have increased, nor that their range has expanded,” the researchers explain in their paper. “Since 2004, Sumatran orangutan numbers have undoubtedly declined, and they continue to do so at an alarming rate because of ongoing deforestation and poaching/persecution.”

And going forward, Wich says Indonesia has the right regulations put in place – they just don’t enforce them.

“Indonesia has a solid set of environmental regulations and protected areas. And if all of these laws would be followed, then the vast majority of orangutans would be safe,” Wich tells The Monitor. “And that’s all were asking for. It is not an outrageous ask, I think, to ask a country to follow its own laws.” 

If current deforestation trends continue unabated, at least 4,500 Sumatran orangutans could vanish by 2030. 

Living exclusively in the North Indonesian island of Sumatra, Sumatran orangutans are one of two remaining species of orangutan. Between 50,000 and 60,000 Bornean orangutans live on the island of Borneo. Besides humans, these two orangutan species are the only great apes living in Asia today.