: Metabolic Adaptation to Climate and Distribution of the Raccoon Procyon Lotor and Other Procyonidae by Mahlke Johnson Kathleen P Mugaas John N Seidensticker John - Raccoon Metabolism Climatic factors; Procyonidae Metabolism Climatic factors; Raccoon Geogra

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Materials and Methods 6 Live-trapping 6 Metabolic Studies 6 Basal and Thermoregulatory Metabolism 6 Evaporative Water Loss 7 Body Temperature 7 Calibrations 7 Calorimeter 7 Body Temperature Transmitters 8 Statistical Methods 8 Estimating Intrinsic Rate of Natural Increase 8 Comparison of Adaptive Units 8

Results 8 Body Mass 8 Basal Metabolic Rate 9 Minimum Thermal Conductance 9 Evaporative Water Loss 11 Thermoregulation at Low Temperatures 12 Body Temperature 12 Summer 14 Winter 14 Thermoregulation at High Temperatures 16 Body Temperature 16 Summer 16 Winter 16 Daily Cycle of Body Temperature 16

Appendix: List of Symbols 29

Literature Cited 30

$Introduction$

DEFINING THE PROBLEM

In the early Tertiary, mid-latitudes of North America were much warmer than they are now, but not fully tropical, and temperate deciduous forests, associated with strongly seasonal climates, occurred only in the far north . Major climatic deteriorations, with their attendant cooling of northern continents, occurred during the Eo-Oligocene transition, in the middle Miocene, at the end of the Miocene, and at about 3 MYBP . This last deterioration corresponds with closure of the Panamanian isthmus . Climatic deterioration went on at an accelerating rate during the late Tertiary, with glacial conditions developing at the poles by the mid-Pliocene . Therefore, throughout the Tertiary, as continents cooled, northern climate zones moved toward the tropics .

These are considered conspecific in some current taxonomies ; however, the scheme followed here maintains them as separate species .

During the late Miocene, late Pliocene, and Pleistocene, the Bering land bridge between North America and Asia formed periodically, offering an avenue for dispersal between northern continents . However, by the late Tertiary, northern continents had cooled to the extent that climate, with its attendant sharply defined vegetative zones, became the major factor limiting dispersal by this route . Those Holarctic mammals that did cross the Bering land bridge in the late Tertiary were "cold-adapted" species associated with relatively cool, but not alpine, climates . Among carnivores this included some canids, ursids, mustelids, and felids . Procyonids, however, did not cross the Bering land bridge into Asia, and Ewer ascribes this to their being an "essentially tropical group." Miocene radiation of procyonids occurred at a time when two of the four major climatic deteriorations were taking place . These deteriorations had the effect of cooling the middle latitudes to the extent that temperate forest forms began to appear in mid-latitude floras, along with a rapid influx of herbaceous plants . The procyonid radiation did not penetrate beyond these climatically changing middle latitudes, which implies that these animals were "warm-adapted," and were, therefore, physiologically excluded from reaching the Bering land bridge. Today, three of the six genera and over half of the 18 species that comprise Procyonidae remain confined to tropical regions of North and South America .

ADAPTIVE SIGNIFICANCE OF THE VARIABLES

EXPERIMENTAL DESIGN AND SUMMARY

ACKNOWLEDGMENTS

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