Because humans are fundamentally cooperative creatures, understanding the evolution of cooperative systems is essential to understanding human social behavior. Of particular interest are public goods scenarios, like neighborhood clean-ups of public parks or even waging war. The persistence of this collective action is enigmatic since an individual's best strategy is "free riding": free-riders reap the benefit of others' actions, but do not contribute to the public good themselves. Despite apparent advantages of free-riding, collective action does persist in human societies, where it often cannot be explained in terms of the benefits of helping relatives. Its similar persistence in the societies of non-human primates suggests that understanding the evolutionary basis of this form of cooperative behavior requires us to look beyond our own species at its close relatives. In non-human primates, however, strategies of individuals that engage in collective action have been very little examined. This project focuses on collective action in wild monkeys and tests different hypotheses about the evolution of this puzzling but persistent form of social cooperation.
PI Marina Cords will lead an international field team in examining communal territorial defense by African blue monkeys. Aggression between groups, carried out almost exclusively by females, is important in this species, which therefore makes a good model system. The field team will collect observational data on the behavior of females in four wild monkey groups, part of a long-studied population in the Kakamega Forest, Kenya. Observations will include participation in between-group aggression, within-group grooming, and feeding tolerance. The team will use the data to evaluate whether females reciprocate cooperation of different behavioral types. For example, do females who participate often in territorial defense receive grooming, or tolerance at feeding sites, from their groupmates more readily than females who participate less often? Do females who develop good reputations by participating more often in territorial defense or grooming receive cooperation more readily when they request it?
Evolutionary studies of behavior focus on the costs and benefits of different behavioral programs. While receiving reciprocated cooperation is one benefit of cooperating, theory suggests other potentially important factors. The research will also investigate how cooperation is related to personal risk, in relation to physical and reproductive condition, and the degree to which partners are relatives. Kin selection theory predicts that cooperation will be nepotistic. Pedigree records and genetic analyses will allow evaluation of both maternal and paternal kinship, and the predictions of kin selection theory will be tested with behavioral data. Fieldwork will thus include collection of fecal samples, from which DNA is extracted for paternity analysis. The DNA analysis, including development of several new markers, will be carried out under the supervision of co-PI Todd Disotell,. Studying the effects of paternal kinship is a new focus in investigations of social cooperation, and the project will provide valuable comparative data on the degree to which paternal kinship drives social behavior.
Broader impacts of the study include training of American and foreign students, both graduate and undergraduate, as well as a post-doctoral researcher. International collaboration with a Kenyan university will also be facilitated. The PI's longterm presence at the field site will continue to contribute to rainforest conservation strategies through a local community-based conservation education program.
