_Body Temperature_
In both summer and winter, T_{b}'s increased during metabolic
measurements at T_{a}'s above T_{lc} (Figure 6). This response also
was seen during metabolic measurements conducted on other procyonids
(Mueller and Kulzer, 1977; Chevillard-Hugot et al., 1980; Mueller and
Rost, 1983; Chevalier, 1985).
_Summer_
During summer our data suggested that the upper critical temperature
(T_{uc}) was higher than 35 deg.C. The lowest rates of oxygen consumption
at T_{a} = 35 deg.C occurred after 1.5 to 2.5 hours of exposure to that
temperature. Prolonged exposure to this temperature in summer did not
make animals restless, and their rate of oxygen consumption was very
stable throughout each measurement. Body temperature responses at
T_{a} = 35 deg.C were recorded from two males and two females that had
implanted radio transmitters. With the exception of one male, T_{b}'s
were maintained near 38 deg.C (Figure 6). The one exception (a male)
maintained its T_{b} at 39.3 deg.C. At T_{a} = 35 deg.C, summer males had
rates of evaporative water loss that were lower than those of summer
females (Figure 4). At this temperature, males dissipated 35% +-6% and
females 56% +-18% of their metabolic heat via evaporative water loss.
Thus, at T_{a} = 35 deg.C, males must have utilized modes of heat transfer
other than evaporative cooling (convective and conductive heat
transfer) to a greater extent than females.
_Winter_
Body temperature, evaporative water loss, and metabolic data indicated
that, in winter, T_{uc} was very close to 35 deg.C. In winter, the lowest
level of oxygen consumption was recorded during the first hour after
the chamber had reached T_{a} = 35 deg.C. Unlike summer, animals became
restless after the first hour at 35 deg.C, at which point their oxygen
consumption increased and showed a high degree of variability. Body
temperature responses at 35 deg.C were recorded from both females that had
implanted radio transmitters. In one case, T_{b} rose from 37.9 deg.C at
the end of the first hour to 40.5 deg.C by the end of the second hour, and
as it did not show signs of leveling off, we terminated the
experiment. We exposed that same animal to T_{a} = 35 deg.C one other time
during winter. In that instance, its T_{b} rose to 40.0 deg.C during the
first 30 minutes and was maintained at that level for three hours with
no apparent distress. The other female elevated its T_{b} from 37.3 deg.C
to 39.0 deg.C during the second hour at T_{a} = 35 deg.C and maintained its
T_{b} at that level for two hours. Thus, during winter, prolonged
exposure to T_{a} = 35 deg.C stimulated more of an increase in T_{b} than
it did in summer. During winter, both males and females increased
evaporative water loss at T_{a} = 35 deg.C (Figure 5) but only to the
extent that they dissipated 35% +-10% of their metabolic heat
production. Thus, even in winter, convective and conductive heat
transfers were still the most important modes of heat loss at this
temperature.