Vol. 23, No. 3 
Page 2 
Ecology and Management of Squirrels - W-66-ft 
C. M. Nixon, 
L. P. Hansen 
In evaluating habitat selection by squirrels, we reduced the number of 
habitat variables potentially important to gray and fox squirrels into a much 
smaller number (10) of uncorrelated component variables by principal factoring 
analysis (MWRL 23(2):2). Factor scores for each of the 10-component variables 
were assigned to each plot. The number of squirrels captured on each plot 
(dependent variable) was related to the 10-factor scores for each plot 
(independent variables) by stepwise multiple regression. The most significant 
and consistent results were obtained by lumping captures into 2 categories: 
total fox squirrels and total gray squirrels. 
The largest number of fox squirrels were associated with upland habitats 
having high densities and high basal areas of white oak, black oak, shagbark and 
tight-bark hickories, and all trees combined. Plots on the edge of the timber 
with high densities and high basal areas of sassafras, honey locust, and crab 
apple also held high densities of fox squirrels. The fewest fox squirrels were 
associated with plots containing high densities and high basal areas of beech and 
low densities of seedling and sapling trees. Low numbers of fox squirrels were 
also found in areas with high densities and high basal areas of ash and tulip. 
Sites preferred as habitat by gray squirrels were ravines with high densities 
and high basal areas of beech and sugar maple; edge habitats dominated by 
sassafras, elm, ash, honey locust, and tulip; and lowland habitats with high 
densities and high basal areas of black walnut and sycamore. Gray squirrels 
apparently avoided upland habitats dominated by white and black oaks. 
Although both fox and gray squirrels utilize some "edge" habitats, each 
species was associated with different types of cover. It is not known if these 
2 species of squirrels preferred their associated habitat or whether competition 
forced occupancy of marginal habitat by 1 of the species. From literature on 
habitat selection by fox and gray squirrels, the association of gray squirrels 
with ravine habitats in which large trees with numerous cavities are abundant 
would be expected, as would the proclivity of fox squirrels for upland oak- 
hickory habitats. It is likely, however, that competition played some role in 
the evolution of these preferences. 
Responses of Prairie Chickens to Habitat Manipulation - W-66-R R. L. Westemeier 
This report further explains the management plan proposed for the hypo¬ 
thetical sanctuary described in MWRL 23(1):2-3. The 10-acre field size in the 
plan may appear as unnecessarily intensive management to those who envision 
prairie chicken habitat as square miles of unbroken prairie grassland. Such a 
view is still characteristic of prairie chicken habitat in the western great 
plains. Sanctuary units in Illinois, however, range in size from 17 to 232 acres 
--not square miles—and these relatively small tracts continue to support higher 
densities of prairie chickens than are found in any other state. 
