Vol. 22, No. 9 
Page 2 
were seeded in 1972, 1974, and 1975 after the roadsides had been graded by 
township road commissioners following road bed improvements. An average of 
0.05 hatched nest per acre was determined for the FCGR in 1978, compared with 
0.12 in 1977 and 0.17 in 1976. Over the past 3 years, twice as many hatched 
nests have been found in roadsides on the block management area (FCMU) as in 
scattered seedings (FCGR). Nest densities on roadsides generally reflect the 
spring densities of breeding hens. 
Next month's newsletter will consider reproductive success and the 
relative abundance of pheasant broods on study areas in east-central Illinois. 
Ecology and Management of Squirrels c . M . Nixon ^ 
L. P. Hansen 
Fox squirrel populations tend toward equilibrium in numbers from year-to- 
year, that is, densities may temporarily increase in late spring and in the 
fall, but the late winter densities are about the same from year-to-year. This 
mean density is a product of the available food and shelter interacting with 
an intrinsic social behavior that is inherent in each species. 
Equilibrium density tends to increase as the habitat improves. As forests 
age and mast supplies and shelter sites increase, the survival prospects are 
improved for additional squirrels that are added to the population--either 
squirrels born on the area or those dispersing into the habitat. 
Short term year-to-year changes do occur, usually the result of climatic 
effects (frosts, hard winters), food shortages (mast failures), or excessive 
predation (over-hunting in small woodlots). The subadult squirrels, who are 
usually subordinate members of the population, are usually most affected by 
these factors, probably because they cannot utilize the remaining food and 
shelters usurped by the dominent adult squirrels. 
If fluctuations in density are upward, above equilibrium level, then 
dispersal rates for squirrels less than 1 -year old increase, fecundity rates 
decline, and mortality increases. This occurred in southeast Ohio in 1 966 
and in North Carolina in 1962. If populations fall below the equilibrium 
level, fecundity improves, fewer young disperse, and the population rises to 
equilibrium again. There is no evidence of a long term predictable cycle in 
fox or gray squirrel abundance in the midwest. 
.... ^ at d° es this discussion have to do with fox squirrel management in 
Illinois? We wish to emphasize two points that must be considered in any 
management program; ( 1 ) There is no substitute for old-growth timber as 
squirrel habitat. Population studies of the occupied ranges of gray and fox 
squirrels have consistently shown squirrel densities to be 2-3 times as high 
in old-growth forests as in second-growth stands. (2) There is an equilibrium 
density in all habitats that cannot be surpassed because of social factors 
within each population. At least for gray squirrels, the addition of supplemental 
food or additional shelter will often lessen social pressures and increase 
populations. The evidence for fox squirrels is not so clearcut, and social 
behavior may be the principal roadblock to achieving higher densities throuqh 
habitat management. 
