Philopatry can arise from lack of a suitable territory (ecological constraints hypothesis) or a potential mate (limited mate hypothesis) outside the natal area. We tested predictions from these hypotheses by creating territorial vacancies with and without potential mates for female prairie voles (Microtus ochrogaster). Standard mark-recapture techniques were used to determine group composition and residency before and after removals. Either all adults, all adult females, or no animals were removed from 1 group within each enclosure. Territorial vacancies stimulated rapid immigration of adult female prairie voles. The presence of adult male(s) on the territory resulted in an intermediate amount of immigration compared to vacant and control territories. Immigrants arrived from neighboring groups more often than expected, suggesting that proximity to territorial vacancies affected replacement. The patterns of immigration observed in this study were more consistent with the ecological constraint hypothesis than with the mate limitation hypothesis.