Poaching Has Caused Bornean Orangutan Populations To Collapse Over The Past Two Decades

The apes are surprisingly resilient, but can do nothing when faced with a gun.

The apes are surprisingly resilient, but can do nothing when faced with a gun. © Serge Wich

The most comprehensive study of orangutan numbers on the island of Borneo has revealed some sobering news. Despite close to half a century of conservation efforts to protect the red ape, their numbers have collapsed, with over 100,000 of the animals lost over the past 16 years.

This startling news is a massive blow to those who have dedicated so much to prevent the Bornean orangutan from slipping into extinction. The latest report, published in the journal Current Biology, has revealed two important details about the species. This first is that there were far more orangutans living on Borneo than ever imagined, and the second that they are disappearing at a much quicker rate.


You’ll be unsurprised to learn that the most dramatic rates of decline in orangutan numbers came from deforested regions and tracts of rainforest turned over to agriculture. But what is most worrying is that the total number of the apes that were lost was greatest in both selectively logged and untouched primary rainforest.

The authors suspect that retaliatory killings, poaching for their meat, and the collection of babies for the pet trade likely have a far greater effect on these populations that many might have assumed were relatively safe.

Fragmented rainforest is still a major problem for the apes. © Marc Ancrenaz

The report was published with the help of 38 international institutions, giving the team an unprecedented view of the apes’ situation. 

It has long been thought that the Bornean orangutan is a highly sensitive species, and can only survive in the most pristine of rainforests. But this is not actually true. “We learned that orangutans are distributed much more widely and also occur in more degraded forest areas and even some plantations,” explained lead author Maria Voigt.


The apes are far more resilient to new environments, able to adapt to new food sources such as acacia and oil palm. It also turns out that despite being the most arboreal of the great apes, the orangutans walk along the ground far more frequently than thought. This all means that the apes are much better at surviving in a fragmented landscape than imagined.

Unfortunately, none of this helps when the animals are being slaughtered by people. “Orangutans are a very slow breeding species, and models used in previous studies indicate that if only one in 100 adult orangutans is removed from a population per year, this population has a high likeliness to go extinct,” said co-author Serge Wich. It is estimated that around three to four out of every 100 are currently being killed.

The positive aspect is not only the adaptability of the apes, but that there are more of them than thought. This means that Bornean orangutans are unlikely to go extinct, but only if those national parks in which they survive are properly protected. 


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