RYSER: VIRGINIA OPOSSUMS (DIDELPHIS VIRGINIANA) IN FLORIDA


 If opossums clearly shifted their area of activity and did not return to the
previously used area, the new location points were excluded or two separate home
ranges were calculated if data were sufficient. For the calculation of average home
range sizes, the data set was restricted to values based on at least 40 location points in
order to reduce the effect of sample size on home range size. Factors associated with
home range size (MCPcorr) were investigated by a partial correlation analysis.
Examined variables included age, body size, tracking period (days), number of
location points (N), and the percentage of total home range size comprised of sandhill
and of old fields and pastures. These are areas of presumably low productivity with
regard to food abundance. Studies on population densities and habitat use of rodents
(Brand 1987; Jones 1989), and an analysis of habitat use of opossums showing that
these two habitats were used significantly less than expected based on their area (Ryser
1990), supported this notion.
 Means were compared for significant differences using student's t-test (two-
tailed). The level of significance was set at 0.05.


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AUG SEP OCT NOV DEC


Figure 1. Distribution (half-hour-intervals), means (arrows), and extremes (1) of the individual onset and end of
nightly activity from August to December. The lower and upper bordering lines represent the time of sunset and
sunrise. Average nightly minimum temperatures of each month are connected by straight lines. Minimum
temperatures varied from 21-220C in August, 19-200C in September, 12-140C in October, 1-16C in November,
and 0-15C in December. Samples sizes for the five months are 35, 16, 17, 43, and 32, respectively. Data from
males and females were pooled.