Vol. 22, No. 10 
Page 2 
Ecology and Management of Sguirrels 
C. M. Nixon, 
L. P. Hansen 
Winter, the season most usually detrimental to wildlife populations, does 
not appear to be particularly difficult for gray and fox squirrels. Indeed, 
survival rates of marked adult fox squirrels during the past 8 winters suggest 
that these squirrels are more likely to survive the winter months than the 
spring and summer months. 
The survival rate of marked adult (1.5 years +) males averaged 64% from 
May through September but increased to 84% from October through April. For 
adult females, the average survival rate increased from 72 % spring-to-fal1 to 
78% from fa 11 - to-spring. 
We believe these survival rates for adult squirrels more accurately reflect 
seasonal differences in mortality than would rates calculated for squirrels 
^1.5 years, which also reflect the high rate of egress associated with younger 
squirrels prior to reaching breeding age. 
During spring and summer, the increased activity associated with breeding, 
caring for preweaned young, and caching food supplies may render adult squirrels 
more vulnerable to predation, disease, and accidents. In winter, adult squirrels 
often spend days or even weeks in a leaf nest or tree cavity. They rarely 
venture far from shelter except to die 1 or 2 buried nuts and return to the snug 
confines of their den. 
Responses of Prair?e Ch ? ckens to H abitat Manipu1 ation R. L« Westemeier 
Management of grassland cover on prairie chicken sanctuaries in Illinois 
has typically involved grass seed harvesting, mowing for weed control, mowing 
for hay, or no disturbance the summer preceding a nesting season. Preliminary 
evaluation of these management approaches may be most feasible on the 232-acre 
Yeatter-Field-McGraw sanctuary unit because of annual consistency in nest-search¬ 
ing effort, high population density, and high nest density. 
Among the best sample sizes, the density of established nests was highest 
in undisturbed cover; however, nest success was higher in meadows harvested for 
grass seed and both types produced the same density of hatches--1 per 4 hectares 
(10 acres) (Table 2). Grass seed harvesting results in (1) weather resistant 
stubble 35-40 cm high, (2) some weed and wcody sprout control, and (3) income to 
help defray land taxes and management costs. 
Among the 4 management categories, mowing for weed control resulted in the 
lowest density of hatched nests and the lowest percentage success. The poor 
results following weed mowing may be due to the weediness, the sparse cover density, 
and often the low cover height (^30 cm) that c'arcctef ice this category. Mowing 
for hay showed the highest nest success and a slightly higher density of hatched 
nests, but the low sample size precludes any strong conclusions about hay mowing. 
Typically, residual cover is lacking as a result of hay mowing, but a compensating 
factor may be the rapid concealment of nests when dense stands of red clover or 
timothy grow quickly from fertile soil. The hay-mowing category has typically 
involved small clutches that are indicative of late establishment or renesting. 
