Exploring Behavior and Social Relationships of a Captive Group of Chimpanzees (Pan troglodytes)

An observational study was conducted on a captive group of chimpanzee, Pan troglodytes to determine the overall behavior patterns, social organization, grooming relationships, and enclosure usage. Adolescence is a very dynamic time for young males and new group dynamics were expected to occur. The aim of the study was to investigate any shifting of social bonds among the group members and changes in the ranks of the two adolescent males. The two adolescent males (Lu and Mugsy) should have been demonstrating dominance behaviors towards the females, towards each other, and exhibiting sexual behaviors. Due to the unique group composition and the handrearing/ peer-rearing background ofthe males, this study also attempted to assess ifthe males of the group expressed species and sex-specific behaviors characteristic of healthy, socially capable male chimpanzees. A variety of behaviors were examined to determine interindividual relationships and to predict which male will be the next alpha individual; however, due to the low frequency of occurrence of dominance and submissive behaviors, proximity and grooming data were the primary behavioral measures.

The data revealed that the males did not exhibit behaviors characteristic of their age and sex. The group remained in a stable state throughout the observation period with no observable status striving behaviors. Overall activity levels were low, with each group member having been stationary for 50%-68% of the observable time. The males did not exhibit sexual behaviors or interest in grooming the females while they were in swell. The group distributed nearly equal amounts of grooming to each male and both males spent nearly equal amounts of time in proximity to other members of the group. Mugsy, however, groomed others significantly more than Lu. Based on previous research, those that groom others more tend to be subordinate. The grooming data analyses determined the group's hierarchical structure to be Debbie < Kerry < Julie < Lu < Mugsy. The data also indicated that Lu is likely to be the next alpha individual when Debbie's status declines as she continues to age. Enclosure usage varied for the males and the females of the group. The patterns of enclosure usage replicated the natural fission-fusion social structure found in wild chimpanzees. The females were found to distribute the majority of their time near the waterfall/second viewing area and the males distributed their time near the first and second viewing area. Although the males and females were most often in separate groups, occasionally they were observed in one group moving through the enclosure or foraging and feeding together.

Overall, this captive group of chimpanzees did not demonstrate behavior characteristic oftheir sex and age. A variety of factors may have contributed to the observed behavior patterns, such as the lack of mixed-ages for each sex, lack of adult male role models, hand/peer-rearing of the adolescent males, and the presence of a strong female coalition; however, this study could not distinguish among these factors.