Who needs a forelimb anyway? Locomotor, postural and manipulative behavior in a one-armed gibbon

Given the predominance of brachiation and other forms of suspension in gibbon locomotion, we compared the locomotor, postural, and manipulative behaviors of a captive, juvenile, one-armed gibbon to the behavioral profiles of his family members. We expected Kien Nahn, whose arm was amputated in response to an untreatable injury approximately 1 year before observations began, to avoid suspensory locomotion, to spend more time immobile, and to be less likely to exhibit postures involving forelimb suspension. Data were collected using scan sampling to record the behaviors and postures of Kien Nahn, his younger brother, and his parents. Additional postural and manipulative behaviors were recorded ad lib. Kien Nahn and his younger sibling had similar activity levels, and although differences in postural profiles existed, they were surprisingly few. Specifically, Kien Nahn spent significantly less time in motion and in non-suspensory forms of locomotion than his brother. When compared to his parents, Kien Nahn was found to be both active and in motion more often, but was less likely to exhibit the forelimb suspension posture. Despite the increased energetic demands associated with one-armed brachiation, Kien Nahn preferred suspensory locomotion to other forms of locomotion. Furthermore, he found unique solutions for foraging and locomoting, often making use of his feet and teeth, and he was generally the first to approach and manipulate enrichment objects. We found no evidence to suggest that Kien Nahn's injury has altered his activity levels. Although the one-armed gibbon displayed slightly different locomotor, postural, and manipulative behaviors than his family members, he seems to have adapted well to his injury. Zoo Biol 0:1-8, 2007. (c) 2007 Wiley-Liss, Inc.