Ecology of Sympatric Fox Squirrels (Sciurus niger) and Gray Squirrels (S. carolinensis) at Forest-farmland Interfaces of Pennsylvania

Abstract

We compared abundance, habitat use and diurnal activity patterns of sympatric populations of fox squirrels (Sciurus niger) and gray squirrels (S. carolinensis) in forest-farmland interfaces in a four-county area of Pennsylvania from August 1995 to October 1996. The mean number of fox squirrels observed was significantly less (F = 21.34, P < 0.001) than that of gray squirrels. Fox squirrel abundances were significantly greater in spring than in summer or fall (F = 6.1, P < 0.01). Habitat use by fox squirrels and gray squirrels was differentiated primarily by the distance to a forest-farmland edge, with fox squirrels using areas closer to the forest edge. Habitat used by fox squirrels was also characterized by fewer short shrubs compared to available habitat. Habitat used by gray squirrels was farther from the edge and had fewer understory trees and logs and a greater basal area of snags compared to available habitat. Gray squirrels were more active in the morning compared to midday (P < 0.001), but activity of fox squirrels did not vary between time periods. We conclude that the relatively sparse populations of fox squirrels coexisting with the more abundant populations of gray squirrels on our study sites differ in habitat use principally with regard to proximity to the forest-farmland edge.