Title
Behavioral responses to the introduction of immature members to a previously established bachelor group of western lowland gorillas (Gorilla gorilla gorilla) (meeting abstract)
Author(s)
Gartland, K.N.;McDonald, M.;Slade, S.B.;Sanz, C.;White, F.
Published
2018
Publisher
American Journal of Physical Anthropology
Abstract
In order to maximize social opportunities, western lowland gorillas (Gorilla gorilla gorilla) in zoos are housed in family or bachelor groups. While wild bachelor groups are transient, all-male groups in zoos may be maintained for many years. These groups should be carefully monitored, as keeping multiple males of different ages classes together, particularly during transitional periods, can result in escalating social tension. In this study, we examined how the bachelor group at the Saint Louis Zoo responded to the introduction of two immature males in 2011. Behavioral data were collected on all group members using 15-minute focal observations with 30-second instantaneous scans, totaling 185.25 hours with equal effort in baseline and transition conditions. A two-way ANOVA was used to determine differences in aggressive and affiliative behavior between individuals and the before and after conditions. There were no significant differences in aggressive behavior either between individuals or between conditions. However, we found significant differences both between individuals (F=8.88, n=30, P<0.01) and between conditions (F-32.76, n=30, P<0.001) for affiliation as well as a significant interaction term (F=13.32, n=30, P<0.01). All individuals displayed an increase in affiliation following the introduction. Overall, we conclude that bachelor groups can endure destabilizing social transitions and remain cohesive social units. Behavioral changes will result from these transitions, but the extent to which they affect certain individuals and the group as a whole may vary. Therefore, longitudinal monitoring of bachelor groups can add to our understanding of the effects of demographic transitions on social behavior.
Keywords
Anthropology;Evolutionary Biology
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PUB22999