“Nobody knows exactly how many orangutans there are in the wild of Borneo and Sumatra. Everybody who says he does is lying”. Interview orangutan expert Dr. Marc Ancrenaz
Trying to get your head around orangutan numbers can be a confusing exercise. Depending who you listen to, orangutan populations are “increasing” or at the “brink of extinction”. Dr. Marc Ancrenaz, Scientific Director at the non-governmental organisation HUTAN, knows how to count orangutans. I talked to him and asked how there can be more and less orangutans at the same time.
While western activists, plantation industries and local governments introduce you their latest orangutan number, Marc and his colleagues step into a 5-seat helicopter to fly over the Borneo rainforest. “More than orangutan numbers, scientists are interested in orangutan trends.” I quickly put my mobile on speaker and catch up taking notes.
“Nobody knows exactly how many orangutans there are in the wild of Borneo and Sumatra. Everybody who says he does is lying. You should imagine this is a species that lives in low density across a big range. They are very difficult to spot and live in remote areas. That makes counting orangutans extremely difficult”.
Marc co-published a study on orangutan loss in Borneo that made headlines in western newspapers. Orangutans numbers are declining indeed, but populations are also bigger than previously thought. “The media always asks us for numbers. When we started counting orangutans 20 years ago in the Malaysian State of Sabah, the official number for Sabah was 600 orangutans. We surveyed orang-utans where people didn’t expect them: in non-protected forests that were degraded or exploited for timber, or that were high up in the mountains… The result was that we identified more than 11,000 individuals for Sabah alone.” More interestingly, it appeared that orangutans did well in sustainably-managed, degraded forest and could even survive in fragmented landscapes.
“We will come to palm oil later.” He comes across as a structured academic with a natural need to tell the whole story. “Counting of orangutan nests used to be done by foot. You would typically count in a small area and then extrapolate your number for the whole of the population distribution area or Borneo”.
The real change we introduced about orangutan monitoring is the use of the helicopter. “In the Kinabatangan, for example, we used to spend half a year counting nests from the ground to cover only 1% of the sampling area. Now we fly over the same area in 6 hours and cover 15% of the population range. This is much more accurate and less time consuming.”
Orangutans build a new nest almost every night. Spotting these nests along a transactional line allows you to calculate the orangutan density. “It doesn’t matter if you miss nests. As long as you know the proportion of what you detect.” Based on proportion of nest builders, nest building and decay rate you can then calculate a range of orangutan numbers in a specific area.
In Sabah, orangutan populations have remained stable for the past 15 years in well-managed logged forests in the central uplands. Better sampling methods gave even higher numbers for some mixed forest landscapes. In eastern Sabah however, the orangutans compressed in fragmented forest due to large scale agriculture development in the 80s and 90s, are expected to decline at unknown rates.
Conservationist like Marc take a pragmatic approach. Also to palm oil. In Ketapang, on the Indonesia part of Borneo, there are companies successfully protecting orangutans by setting rainforest aside. Even Sabah’s intensive palm oil landscape could sustain orangutans if the industry agreed on planting eco-corridors of natural forest across the agricultural landscape.
We need to accept that big animals such as orangutans or elephants can survive in fragmented landscapes and thus we need to protect and to manage them in these non-protected areas. Their numbers might be declining. “But they are still there, and translocating them to move them in nearby forests is not an option”.