Unusual behaviour of captive-raised gibbons: implications for welfare

Unusual behaviours not normally seen in the wild were studied in 52 captive agile (Hylobates agilis albibarbis) and 23 Müllers gibbons (H. muelleri spp) at three locations within the Kalaweit Gibbon Rehabilitation Project. Unusual behaviours included stereotypic behaviour (SB), human-directed masturbation and posterior presenting. These data were collected over 18 months as part of an ongoing study into behavioural adaptation of gibbons in a rehabilitation programme. Data were also collected on the unusual behaviours observed, for example, SB, human-directed masturbation and posterior presenting. I suggest causes of the abnormal behaviours and propose solutions to reduce their incidence in order to improve the gibbon’s progress in rehabilitation. From this study I conclude that most gibbons can be rehabilitated from the point of view of acquiring and maintaining a normal behavioural repertoire once in suitable housing. Encouraging the gibbons to reduce and/or stop these unusual behaviours is key to the welfare of the gibbons while in the rehabilitation programme and to successful release into a forest habitat. An erratum to this article can be found at