SEASONAL ACCLIMATIZATION IN WILD RATS (RATUS NORVEGICUS)

Abstract

Wild rats were collected from dumps at Cornwall, Ontario, and Kingston, Ontario, during summer and winter, and oxygen consumption was measured at various temperatures from 30 °C to −61 °C. Oxygen consumption varied with body weight^0.83 over a size range of 100 to 400 g and was slightly but significantly higher for males than for females. The relation of oxygen consumption to temperature was similar in rats collected during summer and winter over the temperature range from 20° to about −10 °C but at lower and higher temperatures winter rats had higher metabolic rates. When tested at −40° the oxygen consumption of winter-caught rats was maintained for at least 50 minutes while that of the summer-caught rats declined progressively. It is concluded that wild rats exhibit a metabolic acclimatization to seasonal changes in their environment.