Metabolism and thermoregulation in the forest shrew Myosorex varius (Soricidae: Crocidurinae)

Abstract

The forest shrew (Myosorex varius) is grouped with the subfamily Crocidurinae, but recent allozyme evidence suggests that it is intermediate between the Crocidurinae and the Soricinae. It also exhibits some atypical morphological features. Because the two subfamilies have different habits and levels of metabolism, we measured activity patterns, metabolism and thermoregulation of M. varius to assess whether its physiology was consistent with that of the other crocidurines. Metabolic rate within the thermal neutral zone (29–35°C) averaged 38.9 J g⁻¹hr⁻¹, close to expected levels for a mammal of equivalent size. Body temperatures were quite variable, ranging from 33.2–38.3°C and were defended at temperatures as low as 6°C by increased beat production. These data suggest that M. varius is a typical crocidurine. In contrast to other crocidurines, however, M. varius did not enter torpor. They also exhibit differences in their winter activity patterns and may be territorial, suggesting that at least in some respects M. varius does differ from other crocidurines.