Why do some males choose to breed at home when most other males disperse?

ABSTRACT

Dispersal is a key driver of ecological and evolutionary processes. Despite substantial efforts to explain the evolution of dispersal, we still do not fully understand why individuals of the same sex of a species vary in their propensity to disperse. The dominant hypothesis emphasizes movements and assumes that leaving home (dispersal) and staying at home (philopatry) are two alternative strategies providing different fitness. It suggests that only individuals of high phenotypic quality can pursue the most beneficial strategy; the others are left to do a "best-of-a-bad" job. An alternative hypothesis emphasizes settlement decisions and suggests that all individuals pursue a single strategy of choosing the breeding habitat or group with the highest fitness prospects; choosing the natal group (philopatry) and choosing a nonnatal group (dispersal) are then outcomes of these decisions. We tested both hypotheses using a long-term study of a free-ranging population of a group-living carnivore, the spotted hyena. We combined demographic data with data on dispersal-relevant phenotypic traits, breeding-group choice, survival, and reproductive success of 254 males. Our results contradict the best-of-a-bad-job hypothesis: philopatric males and dispersers were of similar phenotypic quality, had similar fitness, and applied similar settlement rules based on the fitness prospects in groups. Our findings demonstrate that the distribution of breeding partners can be more important in shaping dispersal patterns than the costs associated with the dispersal movement. The study provides novel insights into the processes leading to the coexistence of philopatry and dispersal within the same sex of a species.