Summary
Desert shrews (Notiosorex crawfordi; 4 g) enter into daily bouts of very shallow torpor, when restricted in their food intake. These bouts, though interrupted and uneven, last throughout that portion of the day the animals' cages are lighted. Body temperature is apparently regulated by fine adjustments of metabolic heat production in hypothermic as well as euthermic desert shrews. Thus, these animals seem to have two temperature thresholds for thermoregulation or body temperature rheostat settings. One is near 38 °C while the other, near 28 °C is likely used exclusively when energy supplies are low. The coefficient of heat transfer is the same at both body temperatures. Power saved by hypothermic animals at air temperatures between 20 and 25 °C amounts to about 96 mW. This is half of the metabolic power output of euthermic shrews at 20 °C and 80% at 25 °C. These results suggest a compromise between the energy savings of a deep torpor and the unimpaired functioning of euthermia.
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Supported by NSF: DEB 75-18576 and NIH: AM 05738
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Lindstedt, S.L. Regulated hypothermia in the desert shrew. J Comp Physiol B 137, 173–176 (1980). https://doi.org/10.1007/BF00689217
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DOI: https://doi.org/10.1007/BF00689217