Behavioral changes following alterations in the composition of a captive bachelor group of western lowland gorillas (Gorilla gorilla gorilla)

Abstract

Western lowland gorillas (Gorilla gorilla gorilla) in zoos are housed in family or bachelor groups to maximize social opportunities. While wild bachelor groups are transient, all‐male groups in zoos may be maintained for many years. Captive bachelor groups need to be carefully monitored, particularly during periods of demographic transition, due to the possibility for escalating aggression. We examined behavioral changes in a bachelor group at the Saint Louis Zoo following two significant alterations in group composition: (1) the introduction of two immature related males in 2011 and (2) the death of the dominant silverback in 2015. Behavioral data were collected on group members using 15 min focal observations with 30‐s instantaneous scans, totaling 185.25 hr for the first transition and 115.25 hr for the second transition (with equal effort in baseline and transition periods). We found that the addition of the two subadult males resulted in a significant increase in affiliation in the group often initiated by these new younger individuals, while the rate of abnormal and aggressive behavior did not change significantly. The rate of abnormal, aggressive, or affiliative behavior in the group also did not change significantly following the death of the dominant silverback. Overall, we conclude that this bachelor group and potentially others can endure possibly destabilizing social transitions and remain cohesive social units. Behavioral changes will result from transitions, but the effect on individuals or impact on the group will vary. Therefore, longitudinal monitoring of bachelor groups will be essential for effective management during any major changes.

Group Reunion in Zoo European Wildcats Using Cat Appeasing Pheromone (CAP) and Gradual Release of the Animals in the Exhibit—A Case Study

“…At the moment, the low number of published papers dealing with (re)unions is unlikely to represent a high percentage of the actual cases of (re)unions taking place in zoological institutions worldwide. Moreover, published papers tend to deal mainly with highly charismatic social species (such as social primates, wild dogs and elephants [3,[12][13][14][15]), although solitary species can also be kept in groups or pairs in zoos, and such an approach has been found to be beneficial for at least some of them [8,[16][17][18][19]. For example, a quick search on Scopus (https://www.scopus.com/; accessed on 16 November 2021) with the introduction AND zoo AND cat AND social AND group as keywords rendered only one result: a paper on enrichment in tigers, including a general section on social housing [20], although two cases of a semiochemical being used during the introduction of tigers have been published elsewhere [2,21].…”

Social Behaviour in Zoo Bachelor Groups: A Case Study of Related South American Fur Seals

“…Longitudinal management of bachelor groups supports optimal species management [42], and the importance of understanding social networks of animals over time has been highlighted [18]. This research advocates such recommendations in SAFSs.…”

Personality and behavioral changes in Asian elephants (Elephas maximus) following the death of herd members

“…The death of Sithami, a highly central adult female, affected the overall herd dynamic, aside from just her dependent offspring, supporting previous research from Gartland et al . (2018). We also observed changes of a differing nature in the behavior of Sundara, Sithami's eldest offspring, suggesting that the age of offspring is a variable in determining responses to a mother passing.…”

“…2010; Gartland et al . 2018), the loss of a well‐established individual within a group can still impact remaining group dynamics. The sociability of the deceased individual is seen as a primary factor influencing the reactions of others.…”