Orangutans, Pongo pygmaeus, are traditionally viewed as creatures of the forest
canopy, with trips to the ground usually being made only to access specific
resources and extended periods of locomotion on the ground being indicative of
stressed animals struggling to cope with human modification of the environment.
However several recent observations have suggested that Orangutans may spend
more time on or close to the ground than previously thought, illustrating a
need for a more organized, quantitative study of terrestrial behaviour in these
Apes.
In a paper published in the
journal Oryx on 22 January 2015, Brent Loken of the School of Resource and Environmental Management at Simon Fraser University, Chandradewana Boer of the Forestry Faculty at Mulawarman University and Nunuk Kasyanto of Integrated Conservation
describe the results of a 2.5 year camera-trap investigation into the behaviour
of Borneo Orangutans, Pongo pygmaeus
morio, in and around the Wehea Forest in East Kalimantan, Indonesia.
Camera Traps were located in
three types of forest; undisturbed primary rainforest, where there is a dense
canopy but little ground cover, secondary rainforest, which was last logged in
1996, and where the forest has begun to recover, but has a thin canopy and
dense ground cover, and active logging concessions, where the forest still
remains but where desirable trees are being actively removed, and where logging
roads create distinctive breaks in the canopy.
Over the period of two and a half
years from October 2012 until June 2014 Loken et al. recorded 189 instances of Orangutans moving on the ground
in logging concessions, 63 instances in secondary rainforest and 44 in primary
rainforest. While this met the prediction that Orangutans moved on the ground
far more in the logged areas, it also indicated that they spent far more time
on the ground in other areas than previously anticipated. Furthermore the
majority of sightings in the logging concessions were of Apes moving along
rather than across roads, suggesting that they were opportunistically utilizing
Human-created paths rather than moving from one area of canopy to the next
across open ground.
Female Orangutan with newborn infant at the Lamandau River Wildlife Reserve in Central Kalimantan, Borneo. Orangutan Foundation.
Loken et al. suggest that from this evidence Orangutans may be more
terrestrial in nature than previously realized, and that ground locomotion may
be a regular part of their behavioural repertoire, rather than always a
reaction to human-induced environmental stress. They further suggest that this
may indicate that Orang-utans may be slightly more resilient to some forms of
Human intervention in their environment than previously thought, though they stress that these animals
are still extremely vulnerable and cannot survive in heavily altered environments or without extensive forest ranges,
and that areas of managed timber extraction should be included in long-term
management strategies for the species.
See also…
Chimpanzees, Pan troglodytes, like all the Great Apes, face increasing conflict with Humans throughout...
Industrial scale timber extraction began on Borneo in the 1970s and during the period 1980 to 2000 more timber was harvested from Borneo than from Africa and the Amazon Basin combined. In addition much forest has been cleared to make way for monoculture plantations, for the palm oil, rubber and timber industries, as well as being burned in forest fires. For this reason the island is often assumed to be a hopeless case...
Apes (Hominoidea) are large, tailless Primates found in Africa, eastern Asia, and in one case (Homo sapiens) globally. Apes are commonly divided into Lesser and Great Apes, with the 17 species of Gibbon...
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