Community fission, cohesion, and a “Four-Year War” in two populations of wild chimpanzees
Joseph Feldblum, Duke, Evolutionary Anthropology
In 1973, researchers in Gombe National Park, Tanzania, observed the only apparent example of community fission in wild chimpanzees. Over the next four years, males of the northern daughter community killed all adult males and one female of the southern community, and eventually annexed their territory. However, an alternative hypothesis suggests that the two communities were always separate, brought together by human provisioning. Here, we test these competing claims, investigate potential causes of the hypothesized fission, and outline future comparative work to investigate the predictors of social cohesion in chimpanzee communities. Using male association, grooming and ranging patterns from 1967 to 1972, we employed modularity optimizing algorithms to identify the timing and nature of subgrouping, finding a dramatic increase in modularity beginning in 1971, two years before the complete fission. We then aligned this increase with candidate catalysts of the fission to determine likely proximate causes. Finally, we compare Gombe patterns with those in Ngogo, a large community in Uganda that some researchers believe may also be in the process of fissioning, from 2003 to 2008. Modularity in Ngogo rose slowly over the study period, but did not evidence the sharp increase seen in Gombe. I will discuss future work using more data from Gombe and Ngogo to investigate the general relationship between our proposed fission catalysts and modularity in Ngogo and later years in Gombe.
March, 21 2016 | 12:30 p.m. - 2:00 p.m. | Grosss Hall 270