Coming down from the trees: Is terrestrial activity in Bornean orangutans natural or disturbance driven?

Marc Ancrenaz, Rahel Sollmann, Erik Meijaard, Andrew J. Hearn, Joanna Ross, Hiromitsu Samejima, Brent Loken, Susan M. Cheyne, Danica J. Stark, Penny C. Gardner, Benoit Goossens, Azlan Mohamed, Torsten Bohm, Ikki Matsuda, Miyabi Nakabayasi, Shan Khee Lee, Henry Bernard, Jedediah Brodie, Serge Wich, Gabriella Fredriksson, Goro Hanya, Mark E. Harrison, Tomoko Kanamori, Petra Kretzschmar, David W. Macdonald, Peter Riger, Stephanie Spehar, Laurentius N. Ambu, Andreas Wilting

The orangutan is the world's largest arboreal mammal, and images of the red apemoving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down fromthe trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated. http://www.nature.com/srep/2014/140213/srep04024/full/srep04024.html

Scientific Reports 2014; 4: 4024 doi: 10.1038/srep04024

Copyright(C) 2012 PRI (). All rights reserved.