Niche Overlap in Sympatric Populations of Fox and Gray Squirrels

Resource overlap between fox squirrels (Sciurus niger) and gray squirrels (S. carolinensis) has been reported, but quantitative measures of niche overlap in sympatric populations are unavailable. We examined niche breadth and niche overlap in habitat and nest characteristics among sympatric fox and gray squirrels in central Georgia during 1989-90. We used radiocollared squirrels to locate nests and record locations within forested stands. We classified habitat and nest characteristics into 12 niche dimensions: 2 nest and 10 habitat. On several dimensions, fox squirrels occupied narrower niches relative to gray squirrels. Gray squirrels nested in a greater variety of tree species and selected stands with broader ranges in midstory pine (Pinus spp.) stems per hectare and overstory species. Intraspecific niche overlap between species was greater (P < 0.05) than interspecific overlap on 9 of 12 dimensions. Intraspecific and interspecific niche overlap did not differ (P > 0.05) on overstory hardwood stems per hectare, overstory pine per hectare, and midstory tree species. These findings suggest that coexistence between fox and gray squirrels was maintained, in part, through niche partitioning on several dimensions.