Can information sharing explain recruitment to food from communal roosts?

Abstract

The debate over whether communal nests and roosts function primarily as information centers (they facilitate the sharing of foraging information) remains unresolved. Here I use evolutionary game theory to investigate the relative importance of this influential hypothesis and an alternative: that roosts, in particular, function as recruitment centers (they facilitate aggregation at food patches). Basing my model on juvenile common raven (Corvus corax) behavior, I assume there is no net cost to being at food patches in groups, and foragers roost communally. Moreover, one strategic outcome is the observed raven behavior: individuals search independently and recruit from the roost once a patch is found (they play Search-and-Recruit, or SR). I investigate the stability of this in two scenarios that differ in the magnitude of the lost opportunity costs to mutants playing SR in populations of other strategies. When these costs only involve a chance of not being in a group at a located carcass, SR is the only evolutionarily stable strategy under all conditions. However, when these costs also include missing opportunities to be socially dominant, SR no longer enjoys exclusive dominance in the strategy set. Nevertheless, in both cases, there are conditions where group foraging benefits have no effect on the evolutionary stability of SR. Thus, contrary to assertions in the literature, the opportunity to share foraging information can be sufficient to drive the evolution and maintenance of recruitment to food from communal roosts. However, I conclude that both information and grouping benefits are likely to underlie communal roosting behavior in my focal system. Copyright 2002.