Influence of social and environmental factors on nesting behaviour in captive gorillas (Gorilla gorilla gorilla).

Field studies on gorilla sleeping sites usually emphasize environmental influences on nest site selection, as individual nesting behaviours are usually not observed directly. In captivity, nesting behaviour and influencing factors are often overlooked. In the present study, the sleeping sites of members of a captive group of 16-21 gorillas were analysed, based on 152 nights over a 5-year period. Subadults tended to sleep apart from adults but clustered around the oldest blackback male. Full siblings and mothers with offspring were often nearest neighbours. Some sleeping dyads notably endured. Neither age of offspring nor rank of adult females influenced neighbour choice or distances; an interadult distance of 1.5-3 m was typical. Group dynamics were reflected in nesting arrangements. We suggest that possibilities for co-nesting and choice of sleeping sites should be provided to improve the welfare of captive gorillas and other great apes.