Daily Metabolic Patterns of Short-Tailed Shrews (Blarina) in Three Natural Seasonal Temperature Regimes

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Abstract
;An automatic, continuous-flow gas analysis system was used to determine daily metabolic patterns of individual short-tailed shrews (Blarina) in three natural seasonal temperature regimes in eastern Tennessee. Average daily metabolic rates (ADMR) were lowest in the summer (0.426 kcal g•1 day•1), approximately doubled under winter conditions (0.810 kcal g•1 day•1) but were the highest under fall conditions (1.110 kcal g•1 day•1) possibly due to incomplete acclimatization of the shrews. The shape of the daily metabolic pattern for Blarina does not change seasonally; however, summer metabolic rates are the least variable and are lower than most values previously reported in the literature. Polynomial multiple regression analyses were conducted to examine the relative influence of body mass, ambient temperature, and time of day on metabolic rates; only ambient temperature was significant in predicting metabolic rates of this shrew. Average daily metabolic rates of Blarina observed under summer and winter conditions further substantiate the general predictive equations of metabolic rates formulated for small mammals by French et al. (1976). Comparisons of metabolic patterns of Blarina with those of Peromyscus leucopus observed under nearly identical conditions indicate similar rates with strong seasonal influences.