Orangutans Not The Swingers They Were Made Out To Be
July 29, 2013

Orangutans Not The Swingers They Were Made Out To Be

Lee Rannals for redOrbit.com - Your Universe Online

Primatologists writing in the American Journal of Primatology found that great apes spend a large amount of time walking on the ground.

Orangutans have been known as the king of swingers, but finding that the apes come down from the trees to forage or to travel could lead to implications for conservation efforts.

Researchers traveled to the East Kalimantan region of Borneo to a place known as a hotspot for primates, including the Bornean orangutan subspecies, which is the least studied orangutan known.

"Orangutans are elusive, and one reason why recorded evidence of orangutans on the ground is so rare is that the presence of observers inhibits this behavior," said Brent Loken from Simon Fraser University, who led the expedition, in a press release. "However, with camera traps we are offered a behind the scenes glimpse at orangutan behavior."

The team used ground-based cameras across a 23-square-mile region of the forest and captured the first evidence of orangutans regularly coming down from the trees. The researchers said the amount of time the apes were spending on the floor was comparable to the ground-dwelling pig-tailed macaque. Over an 8-month period, the Orangutans were photographed 110 times on the ground, while macaques were seen 113 times.

Although scientists now have a better idea of how often orangutans come down to the ground, the reason they do so still remains a mystery. The team hypothesized that one of the reasons could be the loss of Borneo's orangutan habitat.

"Borneo is a network of timber plantations, agro-forestry areas and mines, with patches of natural forest," said Loken. "The transformation of the landscape could be forcing orangutans to change their habitat and their behavior."

Scientists say that this subspecies of orangutan may be adapted for life in more resource-scarce forests, because they have evolved larger jaws which will allow them to consume more tree bark and less fruit.

"While we're learning that orangutans may be more behaviorally flexible than we thought, and that some populations may frequently come to the ground to travel, they still need forests to survive," said Dr. Stephanie Spehar from the University of Wisconsin Oshkosh in a press release. "Even in forest plantation landscapes they rely heavily on patches of natural forest for food resources and nesting sites."

The region studied, Wehea Forest, is one of the only places in Borneo where ten primate species overlap in their ranges. Since the area is a biodiversity hotspot, paperwork has been submitted to change the status of the forest from "production forest" to "protected forest." Because 78 percent of wild orangutans live outside of protected areas, it is critical that all of the apes there are protected or sustainably managed.

"We do not know how long this may take, but protecting Wehea Forest and Borneo's remaining forests is vital to the long term survival of the orangutans," concluded Loken. "Fortunately 60 percent of Wehea Forest falls under Indonesia's logging moratorium, which helps give legal protection to a large part of the forest for a few more years."