Opportunist road users? Orangutans on the logging roads of Borneo
Opportunistic Behaviour May Show Resilience to Changes in Habitat
An international team of scientists has found evidence that orangutans may be opportunistically choosing to walk on the ground. The 2 1/2 year study used a network of camera traps set in primary, secondary and recently logged forest to document whether orangutan terrestriality differed between the three levels of habitat disturbance. The team’s findings, published in Oryx, indicates that in addition to using trails and ridges, orangutans may be opportunistically using newly constructed logging roads for locomotion.
The team’s research took to them to Wehea Forest in East Kalimantan, Borneo, a large area of 38,000 ha of mostly undisturbed rainforest surrounded by logging concessions. Wehea contains at least nine known species of non-human primate, including the Bornean orangutan and gibbon.
“Discovery that orangutans were using newly constructed logging roads shortly after logging had taken place was surprising. We knew that orangutans used logging roads that had been around for some time, however to use them so quickly may mean that orangutans were opportunistically using these roads for locomotion,” said Brent Loken, from Simon Fraser University Canada. “This finding is important because sustainably logged forests could play an important role in orangutan conservation.”
“Surprisingly, orangutans were also highly terrestrial in primary forest, where there was closed canopy and ample opportunity for moving through the trees,” said Loken. “Previously orangutans were thought to be mainly arboreal, however there seems to be some advantage for them to walk on the ground, even in places where movement through the trees is possible.”
Until recently, terrestrial behavior in orangutans was considered uncommon and used only as a means of acquiring resources. These findings indicate the terrestriality may be a regular strategy employed almost equally by males and females. “We knew that large males tended to walk on the ground,” said Loken. “However we found that males and females, even females with babies, were recorded almost equally walking on roads, trails and ridges.”
“While our findings indicate that orangutans may be opportunistically using newly constructed roads for locomotion and resilient to some level of human disturbance, we must be careful not to reinforce the notion that orangutans can survive in any human-altered landscape,” said Loken. “Orangutans still need trees and lots of them and protection of Borneo’s remaining forests should continue to be of the highest priority for Indonesia and the rest of the world.”
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