Energy metabolism and body water turnover rates of two species of free-living kangaroo rats, Dipodomys merriami and Dipodomys microps

Abstract

1. 1. The energy metabolism and comparative body water turnover rates of two species of kangaroo rats, Dipodomys merriami and Dipodomys microps, were measured in the natural environment over a 1-yr period with the D 2 18O method. 2. 2. In addition to yielding energy metabolism data indicative of active, non-postabsorbtive animals, the results suggest that both species undergo diurnal torpor during periods of cold stress. 3. 3. Comparative water metabolism data indicate that D. merriami possesses a more conservative body water turnover rate than does D. microps. 4. 4. The D 2 18O method of studying animal energy metabolism in the natural environment yields data not obtainable through conventional laboratory methods. It is preferable, therefore, that where practicable this method be employed in investigations of animal physiological ecology unless there is reasonable assurance that laboratory methods are adequate.