Abstract # 100:

Scheduled for Thursday, August 17, 2006 07:00 PM-09:00 PM: Session 8 (Regency West 1/3 ) Poster Presentation

The Effects of Old Age on Social Behavior in Female Captive Chimpanzees (Pan troglodytes)

J. E. Davenport, E. N. Videan and J. Fritz
Primate Foundation of Arizona, P.O. Box 20027, Mesa, Arizona 85277, USA
     Limited research on aged captive chimpanzees suggests that as individuals age they may involve themselves in more non-social activities and have a tendency toward less affiliative and aggressive behaviors. However, previous studies have yielded contrasting results. This study further tested the hypothesis that older female chimpanzees will experience less affiliative and agonistic behavior, compared to younger chimpanzees. This study compared chimpanzees in larger group sizes (5-6 individuals) than has been used in previous studies (2-3 individuals) and incorporated group composition effects as well. Instantaneous scan-sampling, with 30-second intervals, was used to record the behavior of 30 adult female chimpanzees, for an average of 8-9 hours of data per individual. Nine individuals were classified as “old” (mean=37.5 years), while the other 21 were classified as prime adults (mean=20.5 years). The percent of time individuals engaged in various behaviors was compared using a factorial Analysis of Variance model, with significance set at the 0.05 level. Results indicated the older female chimpanzees engaged in significantly less affiliative behavior (F=8.31, p=0.008) and more non-social behavior (F=6.99, p=0.01) than their prime adult counterparts. These results were consistent across social groups, suggesting that group composition had no effect on social and non-social behaviors. Overall findings suggest as female chimpanzees age, they become less social and more solitary, regardless of the age-composition of their social groups.