In this investigation we measured basal and thermoregulatory
metabolism, evaporative water loss, and body temperature of raccoons
from north central Virginia. Measurements were conducted on both sexes
in summer and winter to determine how season and sex influenced these
variables. We then compared the data for this widely distributed
generalist with data from literature for its ecologically more
restricted relatives. Dietary data for all species were taken from
literature, as were reproductive data for calculation of r_{max}.
Our analysis demonstrated clear differences between _Procyon lotor_
and other procyonids with respect to [.H]_{b}, C_{mw}, D_{d}, and
r_{max}. The composite score calculated from these variables for
_Procyon lotor_ was much higher than those derived for other species,
and there was a positive correlation between the number of climates a
species occupies and the magnitude of its composite score. Data on
evaporative water loss, although not complete for all species,
suggested that tropical and subtropical procyonids have less capacity
for evaporative cooling than _Procyon lotor_ or _Bassariscus astutus_.
It was clear, therefore, that with respect to its thermal physiology,
_Procyon lotor_ differed markedly from other procyonids, and we
contend that these differences have allowed this species to become a
highly successful climate generalist and to expand its distribution
into many different habitats and climates. Our analysis also suggested
that the cornerstone of _Procyon lotor_'s success as a climate
generalist is its [.H]_{b}, which is higher than the procyonid norm.