Nest Insulation: Energy Savings to Brown Lemmings Using a Winter Nest

摘要

Energy metabolism of brown lemmings in summer pelage with and without real or artificial nest material was measured over long periods at several air temperatures. Resting metabolism of lemmings at Ta = -16 C was higher than that of lemmings which had nests. At higher Ta the difference between resting metabolism of animals with and without nests decreased and was similar at Ta = 20 C. The energy savings by reduction of heat loss of resting lemmings translates into a ca. 50% decrease in the average metabolic rate. The energy saved at rest is equivalent to a reduction in thermal conductance of roughly 40%. Independent estimates of energy savings due to nest insulation by analysis of cooling curves of a lemming model with and without a nest suggest a 45% change in thermal conductance. Baby lemmings huddled in a nest had equilibrium body temperatures four to five times higher than isolated nestlings outside the nest. These data suggest that there is a substantial energy savings at ecologically relevant air temperatures. If the insulative value of the nest is similar whether the animal is in summer or winter pelage, these data suggest that lemmings could exhibit thermoneutral levels of resting metabolism while in large nests at subnivian air temperatures typical of Barrow, Alaska during the winter.