Energy expenditure in reindeer walking on roads and on tundra

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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.