The energetic cost of various behaviors in the laboratory mouse

The continuous 12-hr observation of a mouse placed in a respiratory chamber has made it possible to record the succession of behaviors of the animal, as well as the associated variations of CO2 concentrations in the chamber. Ten behaviors have been considered; these included rest, locomotion, sniffing, feeding, drinking, nest building and various types of grooming. These data have been used for the estimation, by means of Kalman filtering, of the energetic cost of each behavior. Thus, at 20 degrees C, these costs vary between 1.51 ml CO2/g/hr (rest) and 4.90 ml CO2/g/hr (locomotion). These costs seem independent of any underlying biological rhythm; they yield basal metabolic estimates and average daily metabolic rates similar to those found in the literature. The low energetic cost of each behavioral bout, as compared to the daily energy intake of the mouse, leads one to believe that the behavioral transitions of this animal are not to be ascribed to energetical reasons. These results have been validated with data obtained from two other mice under similar conditions.