Selective Basis For Emigration of the Prairie Vole, Microtus ochrogaster: Open Field Experiment

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Abstract
The hypothesis that for prairie voles, emigrating from an staying in a site are components of a mixed evolutionary stable strategy with emigrants and residents having equal fitness in terms of survival and reproductive activity was tested. It was predicted that emigrants would have greater fitness than residents during colonization of a site since their fitness is reduced between leaving their home site and settling elsewhere. Three populations were live-trapped from 1979 to 1982: 1 control (grid A), and 2 experimental (grids G and I). Voles were allowed to enter and colonize the experimental sites for either 8 or 16 wk intervals, run concurrently. Survival rates of emigrants were higher than those of residents in all cases except for those of adult females on grid G. Reproductive activity of males of both experimental grids, and subadult and juvenile females on grid I was higher than the corresponding group of reidents. The results were thus consistent with our predictions. Females on grid G consistenly had lower fitness than females on the other 2 grids. Grid G seemed to represent suboptimal habitat for females.