Effect of forest patch area on population attributes of white-footed mice (Peromyscus leucopus) in fragmented landscapes

We studied population densities, sex ratios, adult masses, reproductive activity, age structure, and over-summer recapture rates of white-footed mice (Peromyscus leucopus) in 15 woodlots of various sizes and three continuous-forest sites to ascertain the effects of forest patch area on these population attributes. Our study was conducted in west-central Indiana during spring 1992 and 1993 and autumn 1992. Densities of white-footed mice were inversely related to forested area. A survey of previous studies conducted at similar latitudes revealed a similar pattern. Extremely high densities (up to 200 adults/ha) were found in small woodlots (< 0.5 ha). Mass of adult male mice also was inversely related to forest area, and a positive relationship between proportion of adult male mice and forest area was suggested. Ratios of juveniles to adults were positively related to forest area in autumn but not in spring. The proportion of sexually active individuals in the population was not related to forest area, nor were over-summer recapture rates. Our findings indicate that patch area can have dramatic effects on the structure and dynamics of populations of white-footed mice inhabiting fragmented landscapes.