Seasonal Adaptation of Thermoregulatory Heat Production in Small Mammals

Abstract

All animals living in higher latitudes are exposed to seasonal changes in climate and food availability. To cope with the winter cold, most ectothermic vertebrates like lizards and amphibia hibernate in frost-protected shelter to avoid total freezing of body fluids. Endothermic mammals or birds are in no danger of freezing body fluids, but to maintain body temperature between 36 and 41°C they have to spend more energy for thermoregulatory heat production. Therefore, during winter those mammals which sustain homeothermy need to improve their capacities for thermoregulatory heat production to compensate for greater heat loss. This is particularly crucial for small mammals which cannot greatly enhance the thermal insulation of their fur, and must depend solely on their endogenous heat production to maintain normothermia.