Territorial behavior is most prevalent at high population densities.
Population density generally is lowest in spring, highest in fall (sometimes up to about 30/ha; densities as high as 109 and 163 per ha have been reported, Kirkland and Layne 1989).
In Kansas, populations increased initially following grassland fire, decreased in subsequent years (Kaufman et al. 1988, Clark and Kaufman 1990). In Virginia, populations were highest in the year following a large mast crop (Wolff 1996, J. Mamm. 77:850-856).