According to monthly live-trapping records, the body mass of free-ranging female raccoons increased from 3.6 ± 0.6 kg during summer to 5.6 ± 0.8 kg in early winter, and the mass of free-ranging males increased from 4.0 ± 0.5 to 6.7 ± 0.9 kg during the same interval. These seasonal changes in body mass were due to fluctuations in the amount of body fat and represent a mechanism for storing energy during fall for use in winter. In summer, captive and trapped male and captive female raccoons had the same body mass (4.73 ± 0.61, 4.41 ± 0.70, and 4.67 ± 0.88 kg, respectively, [Table 2]). Mass of captive females did not change between seasons, whereas captive males were heavier in winter than summer (p<0.005; [Table 2]). This seasonal change in mass of our captive males was of a much smaller magnitude (0.6 kg) than that observed for wild males (2.7 kg). During winter, captive males (5.34 ± 1.39 kg) were heavier than captive females (4.49 ± 0.98 kg; p<0.005; [Table 2]). Thus, our captive animals maintained a body mass throughout the year that was intermediate to the range of values found for wild raccoons in the same area.
Table 2.—Body mass in kg and basal metabolism (mL O2·kg-0.75·h-1) of Procyon lotor in summer and winter (s.d. = standard deviation and n = number of observations).
| Season and sex | Body mass, ± s.d., | (n) | Basal metabolism, ± s.d., | (n) |
|---|---|---|---|---|
| Summer | ||||
| Trapped male | 4.41 ± 0.70 | (52) | 780 ± 112 | (20) |
| Captive male | 4.73 ± 0.61 | (22) | 680 ± 102 | (8) |
| Captive female | 4.67 ± 0.88 | (41) | 618 ± 92 | (13) |
| Winter | ||||
| Captive male | 5.34 ± 1.39 | (31) | 704 ± 81 | (19) |
| Captive female | 4.49 ± 0.98 | (42) | 667 ± 139 | (25) |
Basal Metabolic Rate
Within thermoneutrality, Ḣb (mL O2·g-1·h-1) was 0.54 ± 0.09 for trapped males in summer, 0.46 ± 0.07 for captive males in summer, 0.42 ± 0.07 for captive females in summer, 0.47 ± 0.06 for captive males in winter, and 0.46 ± 0.10 for captive females in winter ([Figures 2],[ 3]). Ratios of these measured values to those predicted by the Kleiber (1932, 1961:206) equation are 1.28, 1.12, 1.02, 1.17, and 1.09, respectively. To minimize the effect of body size (Mellen, 1963) and to facilitate comparisons between sexes and seasons and between captive and trapped animals, basal metabolism also was calculated as a function of metabolic body size (mL O2·kg-0.75·h-1; [Table 2]). Based on this analysis, trapped summer males had a higher basal metabolism than captive males (p<0.025) or females (p<0.005) in either season ([Table 2]). There was no difference in basal metabolism between captive males and females in either summer or winter, and there was no seasonal difference in their basal metabolic rates ([Table 2]).