An Experimental Study of the Influence of Pelage Pigmentation on Metabolic Rate and its Possible Relationship to Body Temperature Control and Ecological Distribution

In published studies of temperature regulation in homoiothermic animals little if any attention has been directed to pigmentation of the plumage or pelage other than as applied to protective coloration. Indeed, in arctic and tropical animals the adaptations to temperature are essentially those regulating heat conservation and loss through the fur, feathers and skin. In these animals the body-toair temperature gradient can be adapted only by behavioral adjustments (avoidance of direct sunshine, nest building, and hibernation in a few species) as concluded by Scholander et al. (1950). Doubtless, insulation and the animal's ability to withstand heat or cold are of prime importance. Arctic animals are usually so wellinsulated that they are protected against the extremes of cold to which they become exposed. Variability in keeping comfortable exists to some degree in the animal's posture which can affect heat loss or retention. In cases of adequate insulation by fur and fat, skin or fur color obviously would be of less importance than in those animals with only sparse pelage. In poikilotherms, which depend upon