Spatial variation in population density affects dispersal behavior in brush mice

Abstract

Population density can influence all three phases of natal dispersal: departure from the place of birth, searching the landscape, and selecting a new site in which to settle. The direction of the effect of density on dispersal should be affected by the relative costs and benefits of living in an area with high population density. Animals may benefit from high population density due to mate availability and predator risk dilution, but may also face increased competition in high density areas. These conflicting mechanisms should influence the pattern of change in population density between pre‐ and post‐dispersal locations: do dispersing individuals choose to move to areas of higher or lower population density than that at their natal site? We examined the influence of density on dispersal in brush mice (Peromyscus boylii). We documented pre‐ and post‐dispersal locations of individuals using both radio telemetry and live‐trapping, and used a spatially explicit capture–recapture model to estimate density across the landscape. We also tested for a relationship between dispersal distance and local population density at the natal site. Animals tended to settle in areas with higher population densities than where they were born. This pattern held when landscape‐level changes in population density were incorporated: the magnitude of change in local population density between the pre‐ and post‐dispersal locations of a given individual tended to be greater than would be explained by increasing population density across the landscape alone. Further, dispersal distances were shorter when local natal population density was higher.