Behavioural response of a Western lowland gorilla Gorilla gorilla gorilla group to the loss of the silverback male at Zoo Atlanta

At Zoo Atlanta in December 1994 a silverback ♂ Western lowland gorilla Gorilla gorilla gorilla group leader died of cardiovascular disease. The behavioural responses of the remaining members of the group were studied and a variety of individual and social behaviours was recorded. For 3 months following the death of the ♂ there was a significant increase in aggressive display behaviours, such as lunge, quadrupedal stiff stance, displace and head divert, and the mother-offspring relationship intensified. An understanding of the ‘control role’ of the silverback ♂ and the behaviour of group members following changes in social group structure can help zoo managers plan their management strategy when periods of social change are unavoidable.