BEHAVIORAL-EFFECTS OF CHANGING GROUP MEMBERSHIP AMONG CAPTIVE LOWLANDGORILLAS

Group membership was modified among 4 gorilla groups at Zoo Atlanta in an attempt to increase compatibility and sexual behavior. The modific ations ultimately moved 7 adult females among the groups. The moves we re made by individually introducing the new group members to the old m embers, resulting in 18 total introductions. Several individual and so cial behaviors differed in the two conditions. The most obvious change was a temporary increase in aggressive display behaviors, as well as an increase in contact and social examination, in the postmovement con dition. Additionally, the individual behaviors of travelling and eatin g increased after the introductions, while resting decreased. Other se lf-maintenance behaviors did not change. Finally, there was an increas e in time mothers and offspring spent closer to one another following the moves. Previous research and anecdotal evidence suggest that goril las respond to changes in group membership with aggression; these data support and extend those data to different age/sex groups, postmoveme nt trends in behavior, and other aspects of gorilla behavior. (C) 1996 Wiley-Liss, Inc.