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Vol. Ik, Ho. 10 
Page 2 
Ecology and Managemen t of Squi rre 1 s - W-66-R C. M. Mixon, 
L. P. Hansen 
To understand why and to what extent life history characteristics such as 
reproduction and survival fluctuate is to understand why squirrel numbers 
fluctuate and why knowledge of these demographic parameters is essential to 
sound management. As part of a 7~year study of an unexploited squirrel population 
at the Vermilion River Observatory (VRO) near Danville, we live-trapped and marked 
squirrels at 6-month intervals. This permitted life-table analyses and evaluation 
of seasonal and annual variability of both recovery and reproductive rates. 
The life-table analysis indicated that mean annual mortality rates for male 
(3*s%) and female (37%) fox squirrels at the VRO was low compared to mortality 
rates reported in the literature, especially those of exploited populations. For 
fox squirrels less than 1.0 year old, males survived better than females, although 
the differences were not significant. Male and female fox squirrels 1.0 year and 
older had similar survival rates. A comparison of age classes with sexes lumped 
indicated that survival of fox squirrels 0.2 year old at first capture was 
significantly poorer (P < 0.01) than survival of squirrels 0.5 year old at first 
capture; survival of both these age groups was poorer (P < 0.01) than that of 
squirrels older than 0.5 year at first capture. Yearling and adult survival did 
not differ significantly. 
Six-month recovery rates also indicated that survival of young at the VRO 
was poorer and more variable than that of yearlings and adults. At least part 
of the loss of young was due to dispersal off the study area. Fox squirrels 
apparently become 'established 11 some time between 0.5 and 1.0 year, after which 
little dispersal occurs and survival is high. Some adults apparently did 
disperse, as indicated by the capture of untagged adults during some trapping 
periods. Survival of these adult dispersers was significantly poorer (P < 0.01) 
than that of adults that had been tagged as young and remained on the area. 
Apparently these dispersing adults had not established residency but were 
wandering in search of suitable unoccupied habitat. 
In next month's newsletter we will evaluate the factors that most strongly 
influence survival rates. 
Pxes ponses of Prai rie C h ? cken s to l> ab ? tat Man i pul at io n - V/-66-R R.L. Westemeier, 
J.E. Ruhnerkempe 
The number of unsuccessful prairie chicken nests parasitized by pheasants 
has increased with the increase in pheasant abundance at Bogota (Table 2). The 
desertion of unparasitized prairie chicken nests has also increased and may be 
related to pheasant abundance. Chickens deserted their nests at similarly high 
rates in both 1969-73 and 1901, but pheasant numbers were not similar: *»-3 cocks 
in 1969~73 and hZ cocks in 1901. Some nest desertion in 19b9"73 may have been 
due to intra-specific behavior generated by high population density of chickens; 
nest desertion in 1931 may have been due to interspecific pressure from pheasants. 
