By Culturekiosque Staff
LONDON, 12 AUGUST 2013 Orangutans might be the king of the
swingers, but primatologists in Borneo have found that the great apes
spend a surprising amount of time walking on the ground. The research,
published in the American Journal of Primatology found that it is common
for orangutans to come down from the trees to forage or to travel, a
discovery which may have implications for conservation efforts.
An expedition led by Brent Loken from Simon Fraser University and Dr.
Stephanie Spehar from the University of Wisconsin Oshkosh, travelled to
the East Kalimantan region of Borneo. The regions Wehea Forest is a known
biodiversity hotspot for primates, including the Bornean orangutan
subspecies, Pongo pygmaeus morio, the least studied of orangutan
"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 behaviour."
The team positioned ground-based cameras across a 38-square-kilometre
region of the forest and succeeded in capturing the first evidence of
orangutans regularly coming down from the trees.
Orangutans walking on the ground in
Borneo's Wehea Forest.
Photo: Brent Loken
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. Over 8-months
orangutans were photographed 110 times, while the macaques were
photographed 113 times.
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 Borneos 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
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
"While we're learning that orangutans may be more behaviourally
flexible than we thought and that some populations may frequently come to
the ground to travel, they still need forests to survive," said Dr.
"Even in forest plantation landscapes they rely heavily on patches of
natural forest for food resources and nesting sites." 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 hotspot, paperwork have been
submitted to legally change the status of Wehea Forest from "production
forest" to "protected forest". However, given that 78% of wild orangutans
live outside of protected areas, it is critical that all of Borneos
remaining forests are either protected or sustainably managed.
"We do not know how long this may take, but protecting Wehea Forest and
Borneos remaining forests is vital to the long term survival of the
orangutans," concluded Loken. "Fortunately 60% of Wehea Forest falls under
Indonesias logging moratorium, which helps give legal protection to
a large part of the forest for a few more years."
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