A New Orangutan Population on Borneo

Finding a new population of any species is good news in conservation. But finding a hitherto undiscovered population of orangutans (see one in the video above) is really exciting. And we did just that.

In December 2008, we found a significant population of Bornean orangutans. This is some welcome news on a generally gloomy conservation agenda.

Orangutans are among the rarest primates on Earth. Populations are plummeting under the various pressures on their forest habitats. An increasing demand for timber, palm oil, coal and other things desired by the world’s growing human population makes life for orangutans very difficult these days.

So, we all got pretty excited when our field team came back from a survey in a really inaccessible part of Borneo with photos and videos of orangutans. They had traveled to the heart of a 2-million-acre forest area situated in the rugged Sangkulirang limestone mountains in East Kalimantan Province.

Since I first surveyed the vicinity of these mountains in the mid 1990s, I had heard rumors of orangutans in this largely unexplored part of the island. In 2003, The Nature Conservancy organized a major expedition to this same region, and confirmed that at least on the western fringes of the area there were orangutans. But we didn’t expect any significant orangutan populations further east.

Our recent preliminary survey seems to have proven us wrong. Along some six miles of forest transect we found 219 orangutan nests. We cannot yet determine the density from this, but such number generally indicates medium densities of orangutans.

A rapid botanical analysis showed the presence of several orangutan food trees. And because we know that there are very few people in this area and that the forest remains largely untouched, it is quite likely that this area has a population of several hundred orangutans, possibly more than a thousand.

On a total population on Borneo of probably fewer than 50,000 animals, such a find is really important.

The next steps are to work with the local governments to protect these crucial orangutan habitats, and keep orangutan populations from declining further.

The Conservancy is working closely with Indonesian and international partners, including 18 local NGOs, the Indonesian Orangutan Forum, the USAID-funded Orangutan Conservation Services Program, and the Indonesian government, industries, and local communities to develop and implement more coherent and effective strategies to reverse the rapid decline of orangutans.

It’s a struggle, but one that we cannot afford to lose.

(Video: Male orangutan encountered in the Sangkulirang limestone forests. Credit: Nardiyono/TNC.)

If you believe in the work we’re doing, please lend a hand.


  1. The orangutans should be left alone. Once people start going in to protect them, it leads the way for more people. And eventually logging companies start going in due to infrastructure (roads) being set up. Sometimes I think its a better idea to just keep quiet and pretend we never saw them if we really have the greater good of nature/animals in mind.

  2. I agree, the less humans know the better off the Orangutans are. I still find it hard to understand how a country could allow the beautiful Orangutans to become extinct for Palm Oil. The LOVE of money is the root to all evil, and what they have done to the Orangutan is as evil as it gets.

  3. I agree fully with YT and Wanda. We can’t afford loosing one of our closest relatives. In many ways I think orangutans are far ahead of us. They will never destroy the rainforest.
    Please help the Borneo Orangutan Survival Foundation. Look at our Dutch website at “links” and find your own countries partner organisation.

  4. I disagree with YT, for if the Nature Conservancy hadn’t found and documented these orangutans, some other group–probably loggers, miners, or farmers–would have. Environmental groups now, because of this discovery, have the opportunity to work with the government and local people to protect the orangutans.

  5. It is great news, but letting the world know is not the best means of protection. Next will come the ecotourism hordes demanding their personal experience, and there goes what we all say we want to save.

  6. I agree with John. We need to work to make the area protected from loggers or the area will be taken over.

  7. I think humans are the root of all evil. We take, and plunder the earth and its a tragic tragic shame. Orangutans are an amazing species and we have systematically ruined their way of life because some idiots want palm oil? Its repulsive what we do to nature, animals and the world. I dont think that the plan for humans was to become so big and overpopulated. If you think of other species, their populations are controlled by natural phenomena which humans have figured away around. And, because of our dedication to find ways to live longer, build cities, we’ve done it at the expense of a really wondrous world and animal population.

  8. Way to go Erik for all of your great work with the TNC.

  9. It’s great to hear about this encouraging discovery. However, I’m wondering how reliable the nest count method is for estimating total orangutan population size in this forest area. Nest/orangutan densities could not be provided. However, I would think that would be important information to have before making a reasonable estimate. Since orangutans are semi-solitary apes, you’d not be likely to find a high number of them living in a small area. So, if you found a high number of nests in one area, it would be possible for many of those nests to have been built by the same individuals. No? So, I’m hoping that the next step in the research provides more detailed information on the densities and that more actual sightings will verify the existence of different individuals living in the area.

    Another article on this discovery mentions future research plans to use interviews and reports from local people to gather data in a more in-depth census (according to the head of the Indonesian Primate Association and Orangutan Forum): http://m.apnews.com/ap/db_7731/contentdetail.htm?contentguid=1pG8E71C I’m not sure if documenting reports/interviews from the locals will be much more reliable, however. As the NC researchers pointed out, there are “very few people in this area” of the forest which is “largely untouched”. If that’s the case, how will local people be able to report accurately on different individual orangutans living there? Perhaps they will be trained to do this? Of course, I applaud the researchers’ efforts and hope they will keep up their hard work.

  10. Having recently returned from a visit to Borneo I have to say that I was surprised by the number of Orangutans that I saw whilst visiting established natural parks where tourism is controlled. The discovery of this new population is encouraging and important and my view is that this area should be afforded specific protection but at the same time left alone. There are plenty of places where people can already readily see these beautiful animals in their natural environment and there is no need for another. Let’s leave this new population alone but protected so that we can rest assured that somewhere in Borneo there is a completely wild and untouched population that is even free from the click of tourist cameras.

  11. They are discovered so that they can be protect? I doubt so sometimes..

  12. I would prefer to find out and be told it is in an undisclosed location; however, the authorities have been made aware and the area is now fully protected…..what planet am I on?

  13. i like the website to learn about the nature and it is helpful to me

  14. This is fantastic I would like to help the orangutans but the more we try to help them, the more trouble we could cause. So if we leave the oragutans alone, they will be much better off. They know hoe to take care of them selves they have been doing it for years.

  15. Let’s treat these precious creatures as we wish to be treated. The discovery is totally thrilling to us! Is it to them? We would do better to exercise some restraint amid all of our excitement.

  16. Many holiday makers don’t take the time to find out what are the special things that each country they visit are responsible for. Thanks for the awareness as I never new Borneo was home to the orangutan in such numbers.

  17. do u know the population of Borneo??

    1. Sarah, do you mean the entire island, or just the Indonesian part?

      Looks like more than 18 million people for the entire island, and 12 million for East Kalimantan, the Indonesian part.

      Or did you mean orangutan population?

  18. I think all you folks trying to suggest we should ignore them are woefully ill-informed. You seem to have no understanding of reality; you do not grasp how they NEED our involvement in order to persist in the wild.

    Sorry, but you all need to pop out of the holes in the sand and try to see that orangutans need our involvement to continue living in the wild. Not only that, the anthropological information to be gained is astonishing! You seem to run your logic on puppydogs and sunshine, and that’s a joke…

    As for the question about numbers of orangs compared to numbers of nest sites: There is plenty of room for a population in the thousands, and it is simply implausible that these 200+ nests were made by a small number of individuals. The fact that they are generally solitary has been taken into account.

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