FIGURE 2.

Hourly variations in MR (“VO₂”) and respiratory quotient (“RQ”) toward the end of hibernation and after emergence in the common hamster, a food-storing hibernator. During torpor, VO₂ decreases substantially and RQ drops to values close to 0.7, indicating the primary oxidation of lipid to fuel energy requirements at low temperatures. Upon arousals, RQ increases to intermittent values or ∼0.8 (indicating oxidation of mixed substrates), whereas values rise to ∼0.9 at emergence from hibernation and further (0.95) toward the active season. The arrow represents the termination of hibernation, indicating an almost exclusive metabolization of carbohydrates.