Objective To assess the influence of set aside on the spatio-temporal behavior of voles and their impact on adjacent crop fields.Methods A new system for automatic radio tracking was used which allowed tracking at 1 min intervals and up to 1 000 bearings per vole per day.A common vole population living in a set aside was monitored from May to October 2003 and from March to September 2004.Results Voles showed small home ranges with a median size of 125m~2(minimum convex polygon) and 30m~2(Kernel),respectively.Home ranges were stable with a median overlap of 90% for consecutive days,were almost exclusively within the set aside and contained several core areas per range.A poly phasic activity pattern with a phase length of 1.7 h was found during summer with a trend towards diurnal activity.Conclusions Overall set asides were high quality habitats for voles and sustained high population densities without increased risk of voles dispersing into adjacent fields. Objective To assess the influence of set aside on the spatio-temporal behavior of voles and their impact on adjacent crop fields. Methods A new system for automatic radio tracking was used which allowed tracking at 1 min intervals and up to 1 000 bearings per vole per day. A common vole population living in a set aside was monitored from May to October 2003 and from March to September 2004. Results Voles showed small home ranges with a median size of 125m ~ 2 (minimum convex polygon) and 30m ~ 2 (Kernel ), respectively. Home ranges were stable with a median overlap of 90% for consecutive days, were almost exclusively within the set aside and contained several core areas per range. A poly phasic activity pattern with a phase length of 1.7 h was found during summer with a trend towards diurnal activity. Conclusions Overall set asides were high quality habitats for voles and sustained high population densities without increasing risk of voles dispersing into adjacent fields.