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Abstract
We collected nesting data from 512 fresh nest sites, including 3725 individual nests, of western gorillas at the Mondika Research Site, Central African Republic and Republic of Congo from 1996 through mid-1999. The mean count of nests of weaned individuals is 7.4 per nest site. Nest types included bare earth with no construction (45% of total), partial to full ground construction (34%), and arboreal (21%). Females, blackbacks, and juveniles as a combined age-sex class built significantly more arboreal nests (21% of total) than silverbacks did (2%). Proximate rainfall (independent of temperature) is significantly correlated with nest construction, i.e., as rainfall increased, silverbacks built more ground nests, and non-silverbacks built more ground and arboreal nests. Maximum daily temperature (independent of rainfall) is significantly negatively correlated with nest construction, i.e., as temperature increased, gorillas slept more often on bare earth without constructing a nest. Accordingly, we conclude that although nest building in gorillas may have innate components shared with other great apes, it is a flexible behavioral pattern that in some western populations is often not exhibited. It appears that when gorillas in this population build nests, they do so in response to both wet and cool conditions, and independently of diet, ranging, or group size.[PUBLICATION ABSTRACT]