Heat regulation in some arctic and tropical mammals and birds

TLDR: A series of arctic and tropical mammals and birds at Point Barrow, Alaska and in Panama was subjected to various air temperatures in a respiration chamber where the heat production was determined by oxygen consumption or carbon dioxide production.

Abstract: A series of arctic and tropical mammals and birds at Point Barrow, Alaska (lat. 71° N.) and in Panama (lat. 9° N.) was subjected to various air temperatures in a respiration chamber where the heat production was determined by oxygen consumption or carbon dioxide production. The larger arctic mammals and birds showed no increase in metabolism at — 30° C. and from observations on sleeping animals it is probable that their zone of thermoneutrality extends to — 40° C. or — 50° C. The smaller arctic species show a high critical temperature and the tropical species even higher. Metabolic heat production increases rapidly with lowering of the temperature in a tropical mammal or bird, and slowly in an arctic animal. It can be shown theoretically that in a thermoregulated system with a fixed basal energy level and variable insulation the critical gradient is proportional to the maximal insulation and the basal energy level.In a large series of experiments including our tropical and arctic animals, and all animals ...