Conservation news

Orangutans in Indonesian Borneo doomed to extinction?

  • A new study finds orangutans in Indonesian Borneo in unprotected areas are being killed at a rate faster than what population viability analysis considers sustainable.
  • Conflict between orangutans and humans is worst in areas that have been fragmented and converted for timber, wood-pulp, and palm oil production, but hunting is occurring in relatively intact forest zones away from industrial development

Bornean orangutan in Central Kalimantan. Photo by Rhett A. Butler.

A comprehensive new study finds that orangutan populations in Indonesian Borneo are being diminished at unsustainable rates due to conflict with humans. The results suggest orangutans outside protected areas may be headed toward extinction.

The study, published Friday in PLoS One, is based on 18 months of interviews with nearly 7,000 people across 687 villages in areas where orangutans persist in East, Central, and West Kalimantan. The research involved 18 NGOs, including local and international organizations.

The study, which sought to address a dearth of quantitative data on human-orangutan conflict, asked villagers about their knowledge of wildlife laws and orangutan conflict and killing. The researchers tracked responses across age, ethnicity, religion, and livelihoods as well as geography and the villages’ proximity to industrial operations, including oil palm and pulp and paper plantations, mining areas, and logging concessions. Two-thirds of respondents were Dyaks, about a third were Malays and migrants, while less than one percent were punans, who until recently were nomadic forest people.

Crop raiding intensity in different villages across Kalimantan. High = reported conflict frequency every week; Medium = every month; Low = once a year or less frequently. Courtesy of PLoS One.

The assessment, which included responses only from people who were able to reliably differentiate orangutans from other primate species, found that only a small number of people have personally killed an orangutan, but that nearly a sixth of villages reported agricultural conflicts with orangutans and a quarter had killed at least one orangutan. At 18 percent, East Kalimantan had the highest rate of conflict, while West Kalimantan had the lowest at 12 percent.

Crop-raiding by orangutans was commonly cited as a reason for conflict in agricultural areas, while hunting for food was the prime motivation in relatively intact forest zones away from industrial development. Conflict and killing for crop-raiding was most frequent in village areas where palm oil, rice, and industrial pulp and paper was being produced. Those most likely to kill an orangutan were involved with logging, hunting or mining, rather than collection of non-wood forest products.

“Our data suggest that conversion of forests to other land uses can result in orangutans entering villagers’ gardens and raiding crops,” write the authors, led by Erik Meijaard, an ecologist formerly with The Nature Conservancy who now works for People and Nature Consulting International in Jakarta. “This form of direct conflict can result in killing.”

Crop raiding intensity in different villages across Kalimantan. High = reported conflict frequency every week; Medium = every month; Low = once a year or less frequently. Courtesy of PLoS One.

The study found marked differences in the level knowledge between different ethnic groups. 17 percent of respondents were unable to identify an orangutan, but that number was lower for traditional forest people: only 13 percent of Dyaks and less than 0.1 percent of Dyaks failed to distinguish orangutans from other primates. However migrants were considerably more likely than forest people to know that killing an orangutan was against the law. Overall 73 percent of villagers said they knew orangutan-killing was illegal under Indonesian law. 15 percent reported orangutans were protected under customary law known as adat.

The most troubling finding is the scale of orangutan killing, which the study estimated at 750-1790 in past year and 1970-3100 per year on average during respondents’ lifetimes — higher than previously thought.

“These killing rates… are high enough to pose a serious threat to the continued existence of orangutans in Kalimantan.”

Of particular concern is the implied impact of killing female orangutans, which have low reproductive rates due to the extended amount of time they spend rearing their young.

“Population viability studies of orangutans suggest that if annual mortality of females is higher than 1% then populations will go extinct,” write the authors, who go on to estimate the current kill rates of females at 0.9 percent and 3.6 percent, suggesting a dire future for orangutans in Indonesian Borneo.

Bornean orangutan with baby in Central Kalimantan. Photo by Rhett A. Butler.

“These mortality rates caused by hunting alone are higher than the theoretical maximum mortality for population viability, suggesting that unless they can be reduced most Kalimantan populations will go extinct,” they write.

“The data suggest no orangutans outside Kalimantan’s protected areas are safe. They are either threatened by habitat degradation and deforestation, or they are threatened by ongoing hunting within their forest habitats.”

The authors conclude with a call to better target anti-killing measures to specific groups within Kalimantan. They note that because the vast majority of villagers don’t themselves kill orangutans there may be an opportunity to convince those who killing orangutans opportunistically that it is no longer socially acceptable to do so.

Orphaned orangutan in Central Kalimantan. Photo by Rhett A. Butler.

CITATION: Meijaard E, Buchori D, Hadiprakarsa Y, Utami-Atmoko SS, Nurcahyo A, et al. (2011) Quantifying Killing of Orangutans and Human-Orangutan Conflict in Kalimantan, Indonesia. PLoS ONE 6(11): e27491. doi:10.1371/journal.pone.0027491

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