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 cach) were live-trapped 4 May 22 October 1992 and in 14 May 29 October 1993 to examine the effects of patch quality on the population dynamics and dispersal behavior of the meadow vole (Microtus pennsylvanicus). Although enhancing the litter component of vegetative cover did not increase population density or survivorship, reducing the amount of litter and biomass of the standing crop had detrimental effects on population dynamics of meadow voles during 1993, especially early in the growing season. Mean population densities and cumulative recruitment of voles were significantly greater in the control and enhanced-cover treatments compared to the reduced-cover treatment in 1993. Mean body mass of female voles was significantly greater in the enhanced-cover and control treatments compared to the reduced-cover treatment during both years of the investigation. In addition, survivorship of female voles from the founder populations was much higher in the control and enhanced-cover treatments compared to that in the reduced-cover treatment. Significantly greater mean 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 liter). Results show the need to further examine the relationship of vegetative cover and food quality as components of habitat quality for small mammals.