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 Ta 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°C ([Figure 4]). The intercepts and coefficients of the X, X2, and X3 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 X2 (p<0.05) and X3 (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°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 X2 (p<0.05) and X3 (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°C ([Figure 5]).
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.
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.