EFFECT OF ALTITUDE ON OXYGEN CONSUMPTION OF DEER MICE: RELATION OF TEMPERATURE AND SEASON

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Abstract
Metabolic rates of deer mice, P. maniculatus sonoriensis, native to and studied at sea level, 1220 m, and 3800 m were measured at a number of ambient temperatures between 0 and 37 °C. In summer (May–August) there was a direct relationship between metabolic rate and pO2 at all ambient temperatures. When metabolic rates were measured in fall (October–November) at 20 and 32 °C, the MR's of mice from sea level and 3800 m were nearly identical.It is concluded that seasonal changes in MR differ markedly with altitude. At sea level the response to seasonal cold appears ascribable to an increase in physiological insulation. At 3800 m, where summer MR is low, the response to seasonal cold is a metabolic one, that is, an increase in metabolic rate with no change in body temperature.There appears to be no clear-cut relationship between body temperature and altitude and a number of factors other than hypoxia undoubtedly influence not only body temperature, but also thermoregulatory ability of mice from different altitudes.