Changes in nearest-neighbor associations in a captive group of western lowland gorillas after the introduction of five hand-reared infants

The successful. management of a captive gorilla population often necessitat es the hand-rearing of infants and their subsequent re-integration into soc ial groups of conspecifics. In the present study we quantified the changes in nearest-neighbor associations in a group consisting of a silverback male , three adult females, and two sub-adult females after the introduction of five hand-reared infants. Additionally, we examined the associations among kin and non-kin group members to determine whether genetic relatedness was a factor influencing the integration of the infants into the group and the subsequent patterns of association among infants and adults. Results showed that after the introduction, the silverback male spent >60% of his time in close proximity to an infant and 10% of his time within a "cluster" of inf ants. There was a significant,change in a female's nearest-neighbor associa tions; however, the change did not include an infant. The most significant finding among infants was a strong bias by each to associate with another i nfant. When the infants associated with an adult, three of the five associa ted most with the silverback male (P < 0.001), whereas the other two infant s distributed their time among all the adults. The most significant change in behavior patterns was exhibited by one of the sub-adult females who disp layed parental behaviors 18% of the time compared to <1% for all other fema les. Adults and one sub-adult female associated significantly more often wi th related infants compared to unrelated infants (P < 0.025), and the infan ts showed a bias to associate with another related infant (P < 0.0001). Res ults of an infant's association with an adult showed that three of the five infants preferred to associate with a related adult (P < 0.0001). An indiv idual's age, sex, and behavioral profile may have also influenced associati on patterns among group members. These findings lend strong support to the importance of peer groups and the presence of a silverback male for facilit ating the integration of hand-reared infants into established adult groups. Zoo Biol 18:261-278, 1999. (C) 1999 Wiley-Liss, Inc.