VoI, 17, No. 6 
Page 2 
are available to hunters at the beginning of the season in August and September. 
However, squirrels born in July and August, from the second or summer breeding 
season, do not become self-dependent and available to hunters until October, when 
hunter interest is waning. 
The reproductive condition of squirrels in east-central Illinois this past 
spring was unusual. Two study areas in Vermilion County were livetrapped for 10 
days in May for the fourth consecutive spring. The number of adult female fox 
and gray squirrels that had litters this spring was noticeably less than in previous 
years. Also, no juvenile squirrels were trapped. Twenty-four adult female squirrel 
were caught in Hay 1974, and only eight or 33 percent had spring litters. In com¬ 
parison, 75 percent, 84 percent, and 69 percent of the adult female squirrels 
trapped on these two areas had spring litters in 1971 , 1972 , and 1973 , respectively. 
Reasons usually offered for poor spring reproduction in squirrels are mast 
failure and severe winter conditions, which adversely affect the physical condition 
of squirrels, and high population densities and resulting social stress. Other 
researchers have noted a reduction in squirrel reproduction in the winter breeding 
season after a fall mast shortage. One of the major staple mast crops for squirrels 
in Illinois is white oak acorns. There were virtually no white oak acorns available 
last fall in many areas of the state, including Vermilion County, because of a late 
freeze in Hay 1973 that killed the young fruit. Also, the severe cold, the large 
amount of snow, and the long duration of snow cover in December and January of this 
past winter in east-central Illinois may have adversely affected the squirrels' 
physical condition and, therefore, reproduction. 
Trapping of squirrels in southern Illinois, on the Old Barn Sale Area in Pope 
County, this past March yielded different results for the winter breeding season 
(MWRL 17(4):2). A total of eight adult female squirrels were trapped and all had 
spring litters. However, the Old Barn Sale Area consists mainly of large red 
oaks, which take 2 years for their mast crops to ripen. Therefore, the freeze in 
May of I 973 would affect the red oak crop in 1974 and not in l973--as with white 
oaks. Apparently, an ample supply of red oak mast was available to the squirrels 
inhabiting the Old Barn Sale Area. The winter in southern Illinois was also less 
severe than in east-central Illinois and thus allowed squirrels to reach the winter 
breeding season in better physical condition. 
Squirrel reproductive success varies among localities not only because of 
differences in population densities but also because of differences in climate and 
habitat and their interactions, which affect the physical condition of squirrels. 
Responses of Bobwhites to Habitat Manipulation J. A. Ellis 
In 1966 a study was initiated on a 250-acre portion of the Dale Area to 
determine the responses of vegetation and bobwhites to prescribed burning. The 
250-acre zone was divided into 21 plots comprising 125 acres. From 1 966 to 1970, 
half the plots were burned each year. In 1970 and in 1971, all 21 plots were 
burned. In 1972, 16 plots were burned and the prescribed burning program was 
