Energy expenditures for locomotion by barren-ground caribou

Energy expenditure during locomotion on a level treadmill, up and down slopes, and in snow was measured for barren-ground caribou (Rangifer tarandus granti) and compared with that of other species and other subspecies of Rangifer. Highly significant (p < 0.001) linear relationships between [Formula: see text] and walking speed were found for all caribou, indicating that the net cost of walking a given distance was independent of walking speed. The net cost of locomotion (i.e., additional to the cost of standing) for six barren-ground caribou (0.068–0.095 mL O 2 /(g∙km)) was the lowest of any terrestrial species studied. The mean cost of lifting 1 kg of body weight 1 vertical m was 23 kJ/(g∙m) for slope angles of 4.9 to 6.0°. Caribou recovered 6 kJ/(g∙m) during descent for an average efficiency of 62%. The net cost of locomotion in snow increased exponentially with sinking depth. Energy costs of locomotion in crusted snow were often much higher than those in uncrusted snow in which sinking depth was similar. Brisket height, as an index of leg length, was superior to body weight as a predictor of energy costs of walking for a given individual.