Orangutans come down from the trees and spend more time on the ground than previously¹ realised -- but this behaviour may be partly influenced by humans, a new study has found. Dr Mark Harrison, based in the Department of Geography at the University of Leicester and Managing Director of the Orangutan Tropical Peatland Project (OuTrop) has, along with international colleagues, published results of a seven year study of Orangutans in Borneo in the journal Scientific Reports.

 

The research, conducted between June 2006 and March 2013, is based on a large-scale analysis of Orangutan terrestriality using comprehensive camera-trapping data from 16 sites across Borneo. In total there were 641 independent Orangutan records taken at 1,409 camera trap stations over 159,152 trap days.

 

The Bornean Orangutan (Pongo pygmaeus) is the world's largest arboreal² (tree-dwelling) mammal. Records of terrestrial（陆地的） behaviour are rare and tend to be associated with habitat disturbance³.

 

Marc Ancrenaz, from the HUTAN / Kinabatangan Orangutan Conservation Programme in Malaysia, and colleagues conducted the study. Dr Harrison, said: "We've known for some time that Orangutans use the ground to travel and search for food, but the influence of anthropogenic disturbances⁴ in driving this behaviour has been unclear. This is crucial to understand in this age of rampant⁵ forest loss and fragmentation, which is slicing up the Orangutan's jungle home.

 

"We found that although the degree of forest disturbance and canopy⁶ gap size influenced terrestriality, Orangutans were recorded on the ground as often in heavily degraded habitats as in primary forests.

 

"All age-sex classes were recorded on the ground, but flanged⁷ males -- those with distinctive⁸ cheek pads and throat pouches⁹ -- travel on the ground more. This suggests that terrestrial locomotion¹⁰ is a greater part of the Bornean Orangutan's natural behavioural repertoire¹¹ than previously understood and is only modified by habitat disturbance."

 

Dr Harrison added: "The capacity of Orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic¹²（马赛克） landscapes, although the extent of this versatility¹³（多功能性） remains¹⁴ to be investigated."

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