A Behavioural Case Study of Early Social Isolation of a Subadult White-Handed Gibbon (Hylobates lar).

Our aim in this study was to analyse the effects of early social isolation on the behaviour of a white-handed gibbon (Hylobates lar) and at the same time to improve his level of welfare. The subject was a 6-year-old male, isolated from conspecific as well as other non-human primates since he was 3 months old. We presented the gibbon with a series of species-specific vocalisations, and we then introduced a 23-year-old conspecific female into his cage. Our subject did not respond to playbacks, whereas he immediately interacted positively with the conspecific female. After 2 days of presentation, the pair started to spend time in proximity to each other and initiated grooming through the wire-mesh dividing the cages. Four days later we recorded vocal duets. No obvious ste-reotypic behaviours were observed, and the prolonged isolation did not seem to compromise the ability of the young gibbon to socialise with the female conspecific. It appears that prolonged isolation does not always compromise the possibility of recovering socially in a satisfactory manner.