Metabolic rate, maximum metabolism, and advantages of torpor in the fat mouse Steatomys pratensis natalensis Roberts, 1921 (Dendeomurinae)

1.The fat mouse Steatomys pratensis natalensis (mean body mass 37.4±0.43 (se)) has a low euthermic body temperature Tb=30.1-33.8 °C and a low basal metabolic rate (BMR)=0.50 ml O2 g−1 h−1.2.Below an ambient temperature (Ta)=15 °C, the mice were hypothermic.3.The lowest survivable Ta=10 °C.4.Torpor is efficient in conserving energy between Ta=15-30 °C, below Ta=15 °C, the mice arouse.5.Euthermic and torpid mice were hyperthermic at Ta=35 °C.6.Thermal conductance was 0.159 ml O2 g−1 h−1 °C−1, 98.8% of the expected value.7.Non-shivering thermogenesis (NST) was 2.196 ml O2 g−1 h−1 (3.69×BMR).8.Maximal oxygen consumption, however, was 3.83 ml O2 g−1 h−1 (6.44×BMR), indicating that other methods of heat production are additive.9.Because fat mice conserve energy by torpor only between Ta=15-30 °C, we suggest that torpor may be a more important mechanism for surviving food shortages than for surviving cold weather.