Wednesday, 18 March 2015

Terrestrial behaviour in Borneo Orangutans.

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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