EFFECTS OF VEGETATIVE COVER ON THE POPULATION-DYNAMICS OF MEADOW VOLES

Twelve experimental patches of grassland varying in vegetative cover ( reduced cover, enhanced cover, and control; n = 4 each) were live-trap ped 4 May-22 October 1992 and 14 May-29 October 1993 to examine the ef fects of patch quality on the population dynamics and dispersal behavi or of the meadow vole (Microtus pennsylvanicus). Although enhancing th e litter component of vegetative cover did not increase population den sity or survivorship, reducing the amount of litter and biomass of the standing crop had detrimental effects on population dynamics of meado w voles during 1993, especially early in the growing season. Mean popu lation densities and cumulative recruitment of voles were significantl y greater in the control and enhanced-cover treatments compared to the reduced-cover treatment in 1993. Mean body mass of female voles was s ignificantly greater in the enhanced-cover and control treatments comp ared to the reduced-cover treatment during both years of the investiga tion. In addition, survivorship of female voles from the founder popul ations was much higher in the control and enhanced-cover treatments co mpared to that in the reduced-cover treatment. Significantly greater m ean population density and lower per capita dispersal in 1993 compared to 1992 were related to an increase in both components of cover (i.e. , biomass of standing crop and litter). Results show the need to furth er examine the relationship of vegetative cover and food quality as co mponents of habitat quality for small mammals.