The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

The pendular movement in brachiation: A simple model for a locomotion system used in complex environments


1Department of Biology- Functional Morphology group, Antwerp University, Belgium, 2Centre for Research and Conservation, RZSAntwerp, Belgium, 3Department of Anatomy, Catholic University Leuven-Kortrijk, Belgium, 4Department of Movement and Sport Sciences, University of Ghent, Belgium

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Gibbons are known to brachiate using a pendular mechanism, which is thought to be very energy efficient in controlled conditions. However, little is known about how these animals react biomechanically to an unpredictable, complex environment, such as the rainforest they live in. So far, how robust brachiation efficiency is with respect to support compliance has not been tested.

We carry out a kinematic and kinetic comparison (in captivity) of two siamangs, using two setups, to investigate the effect of a compliant branch on gibbon locomotion. Both setups are identical with handholds at the same level, 1.2 m apart and the three middle handholds equipped with force transducers. Only, one setup has all fixed handholds, while the other one has a spring-like handhold in the middle. In total, 30 sequences were analyzed.

Preliminary results lead us to think there are two strategies to cope with the compliant handhold. One animal uses only ricochetal brachiation and although the spring is not skipped, very little force is executed on it. However, judging by the com pattern, it seems the spring is ignored and not used to redirect the com, nor does it affect its position. The other animal brachiates over the spring using slow continuous contact brachiation. Under its weight, the spring elongates, yet the com does not always follow this elongation.

Comparison of energy exchange, collision reduction, forces, joint angles,… on these two setups and between the two strategies will enable us to understand how animals cope with their complex environments.

This study was funded by the National Fund for Scientific Research (Belgium)

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