IMPACT OF CROP HARVEST ON SMALL MAMMAL POPULATIONS IN BROOKINGS COUNTY, SOUTH DAKOTA

Abstract

In the Midwest, agricultural cropland provides the majority of habitat available to small mammals. In some regions of the Midwest, cropland comprises as much as 70% of the landscape. Importance of these agricultural habitats to small mammals pre- and post-harvest is not well documented. The distribution of small mammals was studied in shelterbelt, grassland, and adjacent cropland habitats pre- and post-harvest in Brookings County, South Dakota from 20 September (before crop harvest) to 15 November 2001 (after crop harvest). Deer mice (Peromyscus maniculatus) (n=30) and white-footed mice (Peromyscus leucopus) (n= 29) were captured in relatively high numbers when compared to the other species: short-tailed shrews (Blarina brevicauda) (n=13), masked shrews (Sorex cinereus) (n=7), prairie voles (Microtus ochrogaster) (n=4), meadow voles (Microtus pennsylvanicus) (n=3), and northern grasshopper mice (Onychomys leucogaster) (n=2). Deer mice and white-footed mice were the only inhabitants of cropland. When compared to cropland, proportions of deer mice using the grassland and white-footed mice using the shelterbelt decreased after harvest. Competition among small mammals and predation risks from the short-tail shrew in grasslands and shelterbelts may force deer mice and white-footed mice into habitats such as cropland. Alternatively, the abundance of waste grain after harvest may explain the increased use of cropland. The prairie vole demonstrated a strong use of grassland, while the white-footed mouse used shelterbelt habitats. Cropland habitats adjacent to shelterbelts and grasslands likely provide a relatively stable food source for small mammal populations.