Dynamics of Exploited and Unexploited Fox Squirrel (Sciurus Niger) Populations in the Midwestern United States

Abstract

We examined factors influencing fox squirrel population dynamics in one exploited and two unexploited central Illinois woodlots between 1984–1987. Each fall hunters removed 54–76% of the resident squirrel population on the exploited area during a 50–55 day season. Despite this high annual removal of squirrels during the hunting season, the exploited population was able to attain pre-harvest densities within two to three months following autumn harvests. The reconstituted exploited population was composed largely of immigrants and had a significantly younger age structure than either of the protected woodlots. Reproductive intensities among the three areas were not significantly different. Annual disappearance rates for marked squirrels were significantly higher in the exploited woodlot (79%) than in either of the unexploited areas (44% and 45%). Disappearance rates outside of the hunting season (December - August), however, were not significantly different among exploited and protected populations. Our results indicate that successful recruitment of immigrants allows exploited fox squirrel populations to recover rapidly from hunting induced mortality if an adequate source of recruits is available. Moreover, our results show that hunting mortality is additive in fox squirrels and can greatly increase annual mortality in exploited populations. The maintenance of stable squirrel populations on areas receiving heavy hunting pressure depends on recruitment from nearby refuges or other lightly hunted areas.