METABOLIC RATE AND ITS TEMPERATURE-ADAPTIVE SIGNIFICANCE IN SIX GEOGRAPHIC RACES OF PEROMYSCUS

Abstract

The metabolic rate characteristics of six races of Peromyscus, selected from a wide range of habitats, have been determined over the temperature range 0° to 35 °C. After acclimation to standardized laboratory conditions, critical temperatures and metabolic responses to temperatures below thermoneutrality were largely a function of body size: the larger the mouse, the greater its thermoregulatory efficiency. Body size per se is not correlated with the gross climate of the respective habitats. A single equation which predicts the metabolic rate of these races at any temperature between 0° and 27 °C, from a knowledge of body weight and body temperature, is derived.When considered as a single group, the basal oxygen consumption of all races varied with body weight0,60 over the body weight range of 14.7 to 36.0 g and was insignificantly different from the accepted interspecies approximation. The basal metabolic rates of each race showed no temperature-adaptive differences, especially when considered in relation to body composition. It is concluded that basal metabolic rate is nonadaptive to climate in these races of Peromyscus and consequently has played no important part in their distribution and speciation.