The Benefits-of-Philopatry Hypothesis for the Evolution of Cooperative Breeding: Variation in Territory Quality and Group Size Effects

Abstract

Cooperative breeding systems are characterized by the presence of individuals that remain as nonbreeders in their natal groups past the age of reproductive maturity. Currently, the most widely accepted explanation of this nondispersal is that immature members of cooperative species are faced with ecological constraints on independent breeding, such as habitat saturation. However, current evidence indicates that reproductive opportunities in many noncooperative breeders (where immature individuals always disperse) are just as limited as those in cooperative species. Thus ecological constraints alone cannot explain the differences in the two dispersal patterns. As an alternative, we describe a benefits of philopatry hypothesis, which proposes that nonbreeding helpers remain at home only when there is a net fitness benefit to doing so. This is most likely to occur either when territories in a local area vary greatly in quality or when group cooperation leads to high variance in fitness of individuals in di...