Evaporative water loss increased as chamber temperature increased in
both summer and winter (Figures 4, 5). In summer, the pattern of
increase was different for females and males. Polynomial regressions
for trapped and captive males produced equations that describe a
concave relationship between T_{a} and evaporative water loss, whereas
the equation for females describes a sigmoid curve (Table 4; Figure 4).
For females, water loss increased rapidly at temperatures above 25 deg.C
(Figure 4). The intercepts and coefficients of the X, X squared, and X cubed terms
of the polynomial regression equations (Table 4) were compared
(_t_-tests) to determine if they differed from each other. The
coefficients in the equation for trapped males differed from those for
captive females in the X squared (p<0.05) and X cubed (p<0.025) terms. The
intercept and coefficients of the equation for captive males, however,
were not different from those for either captive females or trapped
males. Although this lack of difference is understandable in the case
of trapped males, where the shape of the two curves is similar
(concave), it is not so clear for the sigmoid curve of captive females
(Figure 4). Perhaps the lack of difference in this case is simply due
to the small number of observations available for captive males (n = 10;
Table 4). Nonetheless, in summer at 35 deg.C, both captive and trapped
males relied less on evaporative cooling than did captive females
(Figure 4).
In winter, males and females had similar rates of evaporative water
loss across the full range of temperatures tested (Figure 5).
Therefore, data for both sexes were combined. The intercept and
coefficients of this equation (Table 4) did not differ from those for
summer females, but they did differ from those in the regression for
trapped males in the X squared (p<0.05) and X cubed (p<0.025) terms. As was
the case for females in summer, rates of water loss for winter animals
increased most rapidly at temperatures above 25 deg.C (Figure 5).
[Illustration: FIGURE 4.--Relationship between evaporative water
loss and chamber air temperature for raccoons in summer: captive
females, open circles; captive males, closed circles; trapped
males, open squares. Lines represent polynomial regressions of
evaporative water loss on chamber air temperature.]
[Illustration: FIGURE 5.--Relationship between evaporative water
loss and chamber air temperature for raccoons in winter: captive
females, open circles; captive males, closed circles. Lines
represent polynomial regressions of evaporative water loss on
chamber air temperature.]
TABLE 4.--Polynomial regression equations describing evaporative
water loss (mg.g^{-1}.h^{-1}) of _Procyon lotor_ in summer and
winter (X = chamber temperature ( deg.C), Y = evaporative water loss,
n = number of observations, R squared = coefficient of determination, and
SEE = standard error of estimate).
--------------+--------------------------------------------------------
Season and sex| Equation (n) R squared
--------------+--------------------------------------------------------
Summer |
Trapped male |Y = 0.1899 + 0.0114.X + 0.0011.X squared - 0.00002.X cubed (32) 0.86
SEE | 0.0885 0.0223 0.0015 0.00003
Captive male |Y = 0.2174 + 0.0192.X + 0.0009.X squared - 0.00003.X cubed (10) 0.73
SEE | 0.3983 0.0834 0.0048 0.00008
Captive |
female |Y = 0.0127 + 0.0943.X - 0.0060.X squared + 0.00013.X cubed (31) 0.64
SEE | 0.2218 0.0547 0.0036 0.00006
Winter |
Captive, |
both sexes |Y = 0.1550 + 0.0426.X - 0.0025.X squared + 0.00006.X cubed (57) 0.80
SEE | 0.0734 0.0192 0.0013 0.00002
--------------+--------------------------------------------------------