Landscape-level correlates of small-mammal assemblages in forest fragmentsof farmland

We studied effects of forest fragmentation on 15 species of small mammals, including 6 species of forest-dwelling granivorous rodents, in the Indian P ine watershed of west-central Indiana. Presence-absence and population dens ities of small mammals were assessed in spring in 35 woodlots of various si zes (0.1-150 ha) and 2 continuous forest sites (>1,000 ha) using live traps in 1992-1996. Presence-absence and population density were related to land scape attributes using logistic and multiple linear regression models, resp ectively. Species richness of forest-dwelling small mammals increased with area and was highest in continuous forest sites. Nested subsets of the full complement of species were found in smaller woodlots. White-footed mice (P eromyscus leucopus) were ubiquitous, and eastern chipmunks (Tamias striatus ) were nearly ubiquitous across the landscape; densities of both species we re related inversely to forested area. Fox squirrels (Sciurus niger) were f ound at 84% of study sites, and they did not respond negatively to isolatio n of forest patches. Red squirrels (Tamiasciurus hudsonicus) were unevenly distributed across the landscape and were found most often in woodlots with large core areas and simple shapes, possibly indicating sensitivity to edg e. Southern flying squirrels (Glaucomys volans) and gray squirrels (S. caro linensis) were restricted to continuous forest sites and >4.6-ha woodlots a djacent to other wooded habitat. Species of small mammals differ appreciabl y in their sensitivities to agriculturally induced fragmentation of forests . Interspecific differences within this assemblage were not due solely, or even primarily, to body size. Rather, differential responses of species to fragmentation likely resulted from variation in habitat breadth and ability to move through an agricultural matrix.