Effects of chronic and intermittent cold exposure on metabolic capacity ofPeromyscus andMicrotus

The effect of 30 days of acclimation at 5°C and of a semiweekly series of short severe cold exposures (T_b 20–30°C) on metabolic capacity (M_max) was measured in Alaskan meadow voles(Microtus pennsylvanicus tananaensis) and Wisconsin deer mice(Peromyscus maniculatus bairdii). Meadow voles, with an M_max of 12–14 ml/(g.h) or 8–9 met (M_max/M_st), showed little response to either treatment. In deer mice, however, acclimation at 5°C increased M_max by about half (from 11.0 to 15.4 ml/(g.h) or from 6.0 to 9.1 met). In 25°C-acclimated deer mice 7 severe cold exposures produced a similar increase of which about half was seen with the first 2 exposures. In 5°C-acclimated deer mice, M_max averaged a 0.3 ml/(g.h) increase for each cold exposure to reach a level of 19 ml/(g.h) or 11 met after 6 weeks.