Abstract
Daily energy metabolism of Peromyscus leucopus and Tamias striatus was measured in three natural seasonal temperature regimes by gas analysis. Average daily metabolic rates (ADMR) were calculated from these daily metabolic patterns. Polynomial multiple regression analyses were conducted to examine the relative influence of body mass, ambient temperature, and time of day on metabolic rates. Several predictive equations are derived from regression analyses which are compared with both the observed data and similar predictive equations of other authors. In both species, ADMRs are approximately double the estimated resting metabolic rates under the same environmental conditions. The method was used to estimate free-living daily energy metabolism of these species in their natural environment. Based on results of the method, there is no significant difference in either species in the metabolic rates of free-living animals and animals living in large, field-located metabolism chambers. For estimating metabolic rates of small mammals whose level of locomotor activity in metabolism chambers is similar to their free-living activity, the method offers no obvious advantages over gas analysis.