There May Be Twice as Many Orangutans as Thought

Researchers explored remote habitats and found evidence that there could be 14,000 orangutans on Sumatra, but deforestation remains a deadly threat.
(Photo: Chaideer Mahyuddin/AFP/Getty Images)
Mar 4, 2016· 2 MIN READ
John R. Platt covers the environment, wildlife, and technology and for TakePart, Scientific American, Audubon, and other publications.

Sumatran orangutans have been dying for some good news, and they finally got some. For now, at least.

According to the results of an extensive three-year survey, Sumatra may hold as many as 14,600 orangutans. That’s more than double the previous population estimate of 6,600 for these critically endangered apes.

A team of researchers crisscrossed Sumatra by foot, walking into remote habitats to find evidence of orangutans in areas where no one had ever looked for them before. They found fresh orangutan nests in mountains, in peat swamps, in western areas of the island that had never been surveyed, and even in partially logged forests.

Nests are the best marker for orangutan presence, since the apes build new nests every night and the old nests take about a year to degrade.

The surveys involved back-breaking work undertaken by a dedicated team of researchers. “Sometimes getting to these sites required a week of walking and then a week to walk back,” said the project’s lead researcher, Serge Wich, a professor at Liverpool John Moores University in the United Kingdom. “The mountains are very steep and unforgiving. That’s why in the past we didn’t go much into those areas.”

The peat swamps also proved more than a little challenging. “You’re up to your waist or higher in very acidic water,” Wich said. “It’s not good for your legs.”

The effort, however, was worth it, as it revealed many more orangutans than they had expected. The apes in the higher elevations, in particular, surprised them. “I certainly did not expect orangutans to be that high up so commonly in almost every area that we went to,” Wich said. “It seemed very common.”

The apes also seemed to be doing fairly well in previously logged areas, although they existed at lower population densities in those regions. “Some of those areas that had been logged by large concessions are growing back to some extent,” Wich said. “That indicates that maybe we can still have some timber harvesting and still have orangutans.”

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Conservationists praised the survey work. “This is excellent news,” said Richard Zimmerman, executive director of Orangutan Outreach, who was not involved in the research. “More individuals means more genetic diversity and a greater chance of survival. The discovery of orangutan populations living in higher altitudes is also great news—especially when it comes to finding suitable habitat to release rehabilitated orangutans or translocating those forced out of their forest homes.”

However, both Zimmerman and Wich pointed out that the threats to orangutans remain very real. Deforestation on Sumatra continues at such a pace that the paper predicts 4,500 orangutans could die on the island by 2030. “The deforestation threat is particularly large because it occurs in the lowland areas where most orangutans are,” Wich said. “Those are the main important orangutan strongholds. If we lose those, we’re not sure what will happen to the highland orangutans.”

Zimmerman added that Sumatran orangutans still should be considered critically endangered due to habitat loss and the illegal pet trade. “The catastrophic situation in which Sumatran orangutans find themselves remains unchanged,” he said. “The long-term survival of Sumatran orangutans in the wild cannot be taken for granted.”

Wich urged people to make buying choices that benefit orangutans—for example, by avoiding buying products containing palm oil—while pointing out that deforestation is not just a threat to apes. “About 20 percent of all greenhouse gas emissions are due to deforestation,” he said. “This is affecting all of us, not just the people of Sumatra and Borneo.”