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Metabolic Adaptation to Climate and Distribution of the Raccoon Procyon Lotor and Other Procyonidae   By:

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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

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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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