The University of Wisconsin Oshkosh’s Stephanie Spehar recently traveled to the East Kalimantan region of Borneo where she helped compile research that showed orangutans spend more time on the ground than what was previously known of these “king of the swingers.”
Spehar is working with Brent Loken from Simon Fraser University.
This sort of research is not new to Spehar, who is the anthropology assistant professor at UW Oshkosh, as she, along with UWO student Eric Fell, found one of the rarest and least known primates in Borneo, Miller’s Grizzled Langur in 2012.
This species was suggested to be extinct or on the verge of extinction, but the team’s findings confirmed the continued existence of the endangered monkey and revealed that it lives in an area where was previously not known to exist.
Spehar’s discovery could not have happened without her semi-permanent research site in Borneo where she conducts research each summer on the behavior of several different primate species.
In Borneo again, the primatologists are uncovering new information on the oragnutans.
Their research has been published in the American Journal of Primatology, which states it is common for orangutans to come down from trees to forage or to travel, a discovery which may have implications for conservation efforts.
“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 behaviour,” said Loken. “However, with camera traps we are offered a behind the scenes glimpse at orangutan behavior.”
The team positioned ground-based cameras across a 38-square-kilometer region of the Wehea Forest, which is a known biodiversity hotspot for primates, including the Bornean orangutan subspecies, Pongo pygmaeus morio, the least studied of orangutan subspecies.
With the cameras they succeeded in capturing the first evidence of orangutans regularly coming down from the trees. During the eight months orangutans were photographed 110 times, while the macaques were photographed 113 times.
Loken and Spehar discovered the amount of time orangutans spent on the forest floor was found to be comparable to the ground-dwelling pig-tailed macaque, Macaca nemestrina, which is equally abundant in Wehea Forest.
This research helps to reveal how orangutans can adapt to their changing landscape; however, this does not suggest they can just walk to new territory if their habitat is destroyed.
The orangutan subspecies P. p. morio may be adapted to life in more resource scarce forests, having evolved larger jaws which allow them to consume more tree bark and less fruit but they are still dependent on natural forests for their long term survival.
“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 Spehar. “Even in forest plantation landscapes they rely heavily on patches of natural forest for food resources and nesting sites.”
The reason orangutans come down from the trees remains a mystery. However, while the absence of large predators may make it safer to walk on the forest floor, a more pressing influence is the rapid and unprecedented 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.”
Wehea Forest is one of the only places in Borneo where ten primates species, including five species found only in Borneo, overlap in their ranges. Since Wehea Forest is a biodiversity hot spot, paperwork has been submitted to legally change the status of Wehea Forest from “production forest” to “protected forest”. However, given that 78 percent of wild orangutans live outside of protected areas, it is critical that all of Borneo’s remaining forests are either 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,” said 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.”