Estimating the Energy Metabolism of Free‐Living Perognathus Formosus: A Comparison of Direct and Indirect Methods

The results of an energy metabolism study of free—living Perognathus formosus, performed with the D_2 ( 18)O method, are compared with data derived from metabolism chamber studies of the same species. Adding an activity correction factor to the metabolism chamber data results in oxygen consumption values essentially no different from those obtained from free—living P. formosus. This agreement was not unexpected, since the two methods share a large common component, i.e., the energy expended for thermoregulation. The agreement was partly fortuitous, however, in that P. formosus happens to behave similarly in nature and in the laboratory. Other species do not so behave. Thus, if prior knowledge is lacking concerning the metabolic behavior of a species in its natural environment, any indirect method of estimating that behavior would have to be validated by a direct method.