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Metabolic Adaptation to Climate and Distribution of the Raccoon Procyon Lotor and Other Procyonidae By: John Seidensticker |
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Metabolic Adaptation to Climate
and Distribution of the Raccoon
Procyon lotor and Other Procyonidae
John N. Mugaas, John Seidensticker,
and Kathleen P. Mahlke Johnson
[Smithsonian Institution logo]
SMITHSONIAN INSTITUTION PRESS
Washington, D.C.
1993
ABSTRACT
Mugaas, J. N., J. Seidensticker, and K. Mahlke Johnson. Metabolic
Adaptation to Climate and Distribution of the Raccoon Procyon lotor
and Other Procyonidae. Smithsonian Contributions to Zoology , number
542, 34 pages, 8 figures, 12 tables, 1993. Although the family
Procyonidae is largely a Neotropical group, the North American
raccoon, Procyon lotor , is more versatile in its use of climate, and
it is found in nearly every habitat from Panama to 60°N in Canada. We
hypothesized that most contemporary procyonids have remained in tropic
and subtropic climates because they have retained the metabolic
characteristics of their warm adapted ancestors, whereas Procyon
lotor evolved a different set of adaptations that have enabled it to
generalize its use of habitats and climates. To test this hypothesis
we compared Procyon lotor with several other procyonids
( Bassariscus astutus , Nasua nasua , Nasua narica , Procyon
cancrivorus , and Potos flavus ) with respect to (1) basal metabolic
rate ([.H] {b}), (2) minimum wet thermal conductance (C {mw}), (3)
diversity of diet (D {d}), (4) intrinsic rate of natural increase
(r {max}), and, where possible, (5) capacity for evaporative cooling
(E {c}). We measured basal and thermoregulatory metabolism,
evaporative water loss, and body temperature of both sexes of Procyon
lotor from north central Virginia, in summer and winter. Metabolic
data for other procyonids were from literature, as were dietary and
reproductive data for all species. Procyon lotor differed from other procyonids in all five
variables. (1) Procyon lotor 's mass specific [.H] {b} (0.46
mL O {2}·g^{ 1}·h^{ 1}) was 1.45 to 1.86 times greater than values for
other procyonids. (2) Because of its annual molt, Procyon lotor 's
C {mw} was about 49% higher in summer than winter, 0.0256 and 0.0172
mL O {2}·g^{ 1}·h^{ 1}·°C^{ 1}, respectively. The ratio of measured to
predicted C {mw} for Procyon lotor in winter (1.15) was similar to
values calculated for Potos flavus (1.02) and Procyon cancrivorus
(1.25). Values for other procyonids were higher than this, but less
than the value for Procyon lotor (1.76) in summer. On a mass
specific basis, Bassariscus astutus had the lowest C {mw} with a
ratio of 0.85. (3) Procyon lotor utilized three times as many food
categories as Procyon cancrivorus , Nasua nasua , and Bassariscus
astutus ; about two times as many as Nasua narica ; and nine times as
many as Potos flavus . (4) Intrinsic rate of natural increase
correlated positively with [.H] {b}. Procyon lotor had the highest
r {max} (2.52 of expected) and Potos flavus the lowest (0.48 of
expected). The other procyonids examined also had low [.H] {b}, but
their r {max}'s were higher than predicted (1.11 1.32 of expected).
Early age of first female reproduction, fairly large litter size, long
life span, high quality diet, and, in one case, female social
organization all compensated for low [.H] {b} and elevated r {max}.
(5) Although data on the capacity for evaporative cooling were
incomplete, this variable appeared to be best developed in Procyon
lotor and Bassariscus astutus , the two species that have been most
successful at including temperate climates in their distributions. These five variables are functionally interrelated, and have
co evolved in each species to form a unique adaptive unit that
regulates body temperature and energy balance throughout each annual
cycle. The first four variables were converted into normalized
dimensionless numbers, which were used to derive a composite score
that represented each species' adaptive unit. Procyon lotor had the
highest composite score (1... Continue reading book >>
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