Field Metabolic Rates of Walrus (<I>Odobenus rosmarus</I>) Measured by the Doubly Labeled Water Method

Abstract

The energy and food requirements of free-ranging pinniped species are difficult to measure and, as a consequence, are unknown for most species. They can be inferred from measures of Field Metabolic Rate (FMR) made by the Doubly Labeled Water (DLW) method, however. In this work, we confirmed our hypothesis that the FMR of pinnipeds measured by DLW can be described by an allometric relationship as a function of body weight. Although costly and difficult to apply, the DLW method is one of the few possible methods generating estimates of energy demands for unrestrained, free-living animals. The results of its application on two adult, male, freeliving Atlantic Walruses (Odobenus rosmarus rosmarus), weighing 1,370 kg and 1,250 kg, respectively, estimated from length and girth measures, are presented here. These data extend the size range of the seven pinniped species for which the DLW method has been applied by a factor of 10. The animals were measured at a site in northeast Greenland (76° N) during the summer. FMR was dependent on the pool model for estimating metabolic rate and was approximately 13% higher when using the single-pool compared with the two-pool model. The estimates using