Conserving energy during hibernation.

How hibernators manage to reduce their high metabolic rate – and therefore energy expenditure – from times when they are active to small almost immeasurable fractions during hibernation has attracted scientific inquiry for over a century. This problemwas also the subject of the classic study by Barbara D. Snapp and H. Craig Heller published in 1981, which presented detailed measurements of different well-identified physiological states as a function of temperature (Snapp and Heller, 1981). It remains a landmark paper in the analysis of metabolic rate reduction during rodent hibernation because it provided measurements of physiological variables over a wide temperature range rather than the narrow ranges that had been previously covered. The paper sparked new interest in the mechanisms of metabolic rate reduction during hibernation and their ecological implications, and resulted in renewed attempts to resolve them.