Metabolic and Behavioral Thermoregulation in the Long-Tailed Vole, Microtus longicaudus

Abstract

The difference between the mean standard metabolic rates of Microtus longicaudus acclimated to 15°C (2.62 cubic centimeters 0₂ per gram-hour) and those acclimatized at natural temperatures averaging 11°C (2.67 cc 0₂/g-hr) is not statistically significant. These values are 60 to 70 per cent higher than predictions based on body weight. The relationship of oxygen consumption to ambient temperature (0 to 40°C) was determined for voles in and out of their nests. The zone of thermoneutrality while in the nest (20 to 30°C) was 5° wider than when not in the nest (25 to 30°C). The relationship of oxygen consumption to ambient temperature below thermoneutrality was linear, described by the equation Y = 5.54 − .146X (in the nest) and Y = 7.26 − .181X (out of the nest). Above thermoneutrality, the relationship becomes curvilinear and is described by the equation log Y =.455 − .017X. Visual observations at temperatures above thermoneutrality revealed no special behavioral patterns for thermoregulation. Body temperature of M. longicaudus was independent of ambient temperature between 5° and 25°C, averaging 37.4°C.