Energy expenditure in reindeer walking on roads and on tundra

The oxygen consumption, VO2, of two adult female reindeer (Rangifer tarandus L.) was measured while walking on roads, wet and dry tundra, and on level ground and gradients of 5 and 9%. The oxygen cost of horizontal walking on the road (S, 0.099 ± 0.009 ml O2/g per kilometre) was 14% higher than that for the interspecies line for mammals given by S = 8.46 W−0.4, where W is body weight (grams). S increased significantly to 0.112 and 0.137 for horizontal walking on dry and wet tundra, respectively. In two human subjects, the oxygen cost of horizontal walking on roads (S, 0.096 ± 0.013) was similar to reindeer; however, on dry tundra S increased 40% more than in reindeer. The mechanical efficiency of reindeer walking up 5 and 9% grades was 50 and 32%, respectively, and the VO2 in walking up a 5% gradient was 1.4 times greater than walking down; the VO2 in walking up a 9% gradient was 1.9 times greater than walking down. Resting metabolism of the two reindeer used in walking experiments varied markedly (120–204 kcal (502–854 kJ)/kg0.75 per day); for a group of four adult female reindeer taken from late summer grazing, resting metabolism was 125 ± 8 kcal (523 kJ)/kg0.75 per day, which was similar to previous estimates for reindeer.