Vol. 23, Ho. 10 
Page 2 
Ecology and Management of Squt rrels - V/-66-R 
C. K. M i xon , 
L. P. Hansen 
V/ i thin an unexploited (unhunted) fox squirrel population that We studied 
near Danville, Illinois, the proportion of adult (1.5 years +) and yearling 
female fox squirrels breeding during the 2 main breeding seasons (spring «* Jan- 
Mar, summer * May-July) was negatively correlated with the number of squirrels 
(both sexes) present during the breeding season (jr = -.522) (Ml/RL 23(7):2). This 
correlation suggests that squirrel density is an important regulator of breeding 
rates and may account for the considerable difference in the number of females 
that breed in spring vs. those that bread tn summer (Table 2). 
These breeding rates are significantly lower (P<0.01) in the summer for 
the 1.5" and 2.0-year classes. The difference in yearling breeding rates 
approached significance (0.10>P>0.05). Squirrel densities increase in May 
and June as the spring-born young are weaned and leave the natal den. This 
period coincides with the time the summer young of the previous year (yearlings) 
also disperse, creating a potential for considerable conflict between resident 
and immigrating squirrels. He do not know if social interaction at this time 
creates stress among breeders that blocks the normal estrous cycle or if agonistic 
behavior between potential breeders actually represents a denial of access to 
the food and shelter that females need to stimulate the reproductive hormones 
leading to estrus. 
Table 2. Percentage of female fox squirrels breeding in each age class during 
the spring and summer breeding seasons. 
Age at 
breeding 
(years) 
Spri ng 
Summer 
M umber of 
females 
Humber 
breeding 
Percent 
breeding 
Humber of 
females 
Humber 
breeding 
Percent 
breeding 
.8 
32 
0 
0 
61 
0 
0 
1.0 
42 
12 
28.6 
10 
0 
0 
1.5 
us 
36 
73.5 
33 
8 
24.2 
2.0+ 
114 
87 
76.3 
80 
35 
43.7 
Totals 
237 
135 
56.9 
184 
43 
23.4 
Responses 
of Prairie 
Chickens to 
Habitat Manipulation-H-66 
-R R.L. 
J.E. 
Westemeier, 
Buhnerkempe 
During late spring and summer of 1920, 464 acres of nest cover on sanctuaries 
were systematically searched for prairie chicken nests. Mests of other grassland 
birds and mammals were also recorded. In Jasper County, 27 prairie chicken nests 
were found in 447 acres of nest cover. Among 24 nests of known fate at Bogota, 
12 were hatches. This level of 50% hatch success usually indicates a stable 
population between spring counts (MWRL 22(9):3). All 12 nest losses were due to 
predation, primarily by the striped skunk. 
