title: Nest insulation: Energy savings to brown lemmings using a winter nest.
abstract: Energy metabolism of brown lemmings in summer pelage was measured over long periods at several air temperatures, with and without a real nest or artificial nest material. Resting metabolism of lemmings at Ta=-16°C was 43% higher than that of lemmings in nests. As Taincreased, the difference between resting metabolism of animals with and without nests decreased and was similar at Ta=20°C. The energy saved at rest is equivalent to a reduction of approximately 40% in the thermal conductance. 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 46% reduction in thermal conductance due to the nest. At Ta=0°C, baby lemmings huddled in a nest had equilibrium temperature excesses (Tb-Ta) four to five times higher than isolated nestlings outside the nest. These data indicate that there is a substantial energy savings at ecologically relevant air temperatures, and that energy savings increase as Tadecreases. If the insulative value of the nest is similar whether the animal is in summer or winter pelage, these data suggest that heat production of a resting lemming would be 0.88 W (about 1.6 times BMR), while in nests at subnivean air temperatures typical of Barrow, Alaska, during the winter.
authors.affiliation: Coordinated Department of Physiology, Cook College, Rutgers University, 08903, New Brunswick, NJ, USA.
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Casey