The Effect of Female Prairie Vole (Microtus ochrogaster) Immigrants on Space Use of Conspecific Female Residents

We tested the hypothesis that female prairie vole (Microtus ochrogaster) residents change their space use patterns in response to immigration pressure. We established prairie vole populations in four 32 × 32-m enclosures during 2000 and 2001. Four populations were supplemented with adult female immigrants and the other four served as control populations in which no females were introduced. Using radio-telemetry, we monitored and compared the home ranges and movement distances of residents vs. immigrants within the same enclosures and residents in enclosures with and without immigrants. Immigrants had significantly larger home ranges and moved greater distances during the evening hours than residents. Resident home ranges and hourly movements were unaffected by the presence of immigrants. The results suggested that resident females could successfully defend their territories without changes in their home ranges and movement distances. However, due to our experimental design, we could not exclude the possibility that female immigrants affected the space use of male residents.