Social influences on intergroup transfer by pine voles (Microtus pinetorum)

Selection to obtain mating opportunities is hypothesized to be a major fact or in dispersal. Thus, if individuals move to another group or switch nests to maximize their reproductive opportunities, they should move to groups o r sites where they minimize competition for resources or mates and where th ey can find potential mates. We examined movement of pine voles (Microtus p inetorum) in an orchard habitat. Males dispersed later than females, but th e two sexes showed similar patterns of movement with respect to conspecific s. Males and females immigrated to territories that contained some opposite -sex conspecifics; they also immigrated to territories without same-sex con specifics. The latter suggests that they may avoid competitors and move to territories where an opening exists. When female breeders were removed from a social group, a replacement female arrived and began to breed relatively rapidly. In control groups where breeding females were not removed, no rep lacement females appeared. These results suggest that pine voles, at least females, may monitor vacancies and immigrate if a vacancy appears.