Metabolism of Weasels: The Cost of Being Long and Thin

Metabolism of cold stressed weasels is 50—100 per cent greater than that of normally shaped mammals of the same weight. This can be attributed to their greater surface area, shorter fur, and inability to attain a spherical resting posture. In evolving an elongate shape which enables them to enter confined spaces in search of prey, weasels have sacrificed energetic efficiency. Increased ability to obtain prey, made possible by elongate shape and sexual dimorphism in body size, apparently more than compensates for the energetic cost of being long and thin. The information on weasels indicates that body surface area is an important determinant of heat loss in small homeotherms and suggests that energetic efficiency has played a significant role in the evolution of body shape and size.