Orangutans are proving more adaptable than expected when it comes to getting around, giving them a better chance of survival as their homelands are carved up for logging.
Dr. Brent Loken placed 97 movement-triggered cameras in orangutan habitat in East Kalimantan, Borneo. The cameras were placed in three types of areas: primary rainforest with full ceiling canopy and complex understory, secondary forest recovering from damage, and recently logged areas.
In total, the cameras operated for 28,485 days and nights, and recorded 296 visits from the endangered species.
Image Credit: SFU - University Communications
The behavior of the great apes varied by the type of forest. In the logged areas, the Pongo pygmaeus morio were more inclined to use the ground to get around than to swing through the trees. There is an obvious explanation for this: logged forests have less tree canopy to swing through. But in Oryx, Loken concludes that this is not the whole story.
“Orangutans were also terrestrial [walking on the ground] in primary forest, where there was a closed canopy and ample opportunity for moving through the trees,” Loken writes. While there were previous reports of adult males choosing legs over arms as the preferred method of locomotion, Loken reports, “Males and females, even females with babies, were recorded almost equally walking on logging roads, trails and ridges."
“Our results indicate that orangutans may be more terrestrial than previously thought and demonstrate opportunistic behavior when moving through their environment, including using newly constructed logging roads for locomotion, possibly indicating some degree of resilience to human disturbance.”
Loken is concerned his work may be misused, stressing, "We must be careful not to reinforce the notion that orangutans can survive in any human-altered landscape. They still need trees and lots of them, and the protection of Borneo's remaining forests should continue to be of the highest priority for Indonesia and the rest of the world."
Nevertheless, the findings suggest that there may be ways to integrate human activity in rainforests in ways that do not harm our close relatives and fellow people.
Loken is a former secondary-school principal who gave up teaching to explore the ways both sustainable and environmentally damaging land-use practices affect local communities. Three years ago, his work made headlines when his cameras picked up an image of a Miller's grizzled langur, a type of monkey previously considered extinct.
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