Selective basis for emigration of the prairie vole, Microtus ochrogaster: open field experiment.

Tested the hypothesis that for prairie voles, emigrating from and 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. Emigrants were predicted to 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 1979-82: a control (grid A), and experimental (grid 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 on both experimental grids, and subadult and juvenile females on grid I was higher than the corresponding group of residents. Results were consistent with 4 predictions. Females on grid G consistently had lowest fitness. Grid G seemed to represent suboptimal habitat for females.-from Authors