On the evolution of delayed recruitment to food bonanzas

Whereas food sharing by immediate recruitment to food bonanzasis relatively common, especially among birds, delayed recruitmentfrom overnight roosts is comparatively rare, although it hasbeen studied extensively in the common raven (Corvus corax).Two hypotheses have been advanced to explain the evolution ofdelayed recruitment. Under the status-enhancement hypothesis,delayed recruiting is favored because the recruiter's social statusincreases with the number of followers it leads to a food source.The posse hypothesis also focuses on the number of individualsrecruited to a site, but in this case aggregation is favoredbecause larger groups are more likely to usurp a carcass defendedby a pair of territorial adult ravens. We used a game-theoreticmodel to explore the logic of immediate versus delayed recruitmentin the light of these hypotheses. In particular, we identified threecritical values of the probability of immediate recruitment:that below which delayed recruitment is a cooperative strategy,that below which delayed recruitment is an evolutionarily stablestrategy, and that below which a mutant strategy of delayedrecruitment will invade a population of immediate recruitersto reach fixation. The model demonstrates that either status enhancementor the posse effect may alone suffice for the evolution of delayed recruitmentto food bonanzas via mutualistic information sharing at communal roosts.