Influence of Social and Environmental Factors on Nesting Behaviour in Captive Gorillas (Gorilla gorilla gorilla)

Abstract

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.

Kin, Daytime Associations, or Preferred Sleeping Sites? Factors Influencing Sleep Site Selection in Captive Chimpanzees (Pan troglodytes)

“…It is notable that the younger males, Kindia and Liberius, and the low-ranking Ricky rarely retired to the OE area, possibly to avoid any conflict with the higherranking males. Zoo-housed blackback gorillas similarly tended to remain out of view of the group silverback [Weiche and Anderson, 2007].…”

“…In contrast, data from captive apes suggest that the presence of kin and other socially affiliated individuals can influence sleep site choice. Weiche and Anderson [2007] reported strong associations between kin, including siblings and mother-offspring pairs, in zoo-housed gorillas: kin and unrelated female dyads that frequently associated during the daytime continued their association at night. Riss and Goodall [1976] reported that sleeping partner preferences reflected long-standing social bonds in captive subadult chimpanzees that had been reared together in small subgroups.…”

“…Thus, medium-sized gorillas nested approximately 1.5 m from each other and less than 1 m from juveniles, but around 4 m from silverback males. Closely affiliated gorillas may nest in closer proximity to each other [Hess, 1992, in Weiche andAnderson, 2007]. Socially lowranking bonobos have been observed to sleep at the periphery of the nesting party [Fruth and Hohmann, 1994].…”

“…Data from captive apes also indicate preferred sleeping sites. Zoo-housed gorillas, for example, slept in specific rooms within their indoor enclosure significantly more frequently than other available rooms over several years, suggesting enduring preferences for these areas [Weiche and Anderson, 2007]. To date, there have been no studies that have specifically focused on sleeping site preferences in captive chimpanzee groups.…”

“…We predicted that captive chimpanzees who frequently associated during the daytime, and kin-related individuals, would sleep in the same locations, after Videan [2006] and Weiche and Anderson [2007]. Further, it was predicted that each individual would show a clear preference for a particular sleeping site.…”