Coat color is predominantly brown to olive, with whitish underparts, buttocks and legs, but there is a great deal of geographic variation. Some populations in Greenland and northeastern Canada have nearly white coats. Both sexes are antlered. The feet of these animals are broad and flat with deeply cleft hooves. The structure of their feet presumably allows them to navigate the winter snows and the summertime spongy arctic tundra.
Tendons snap across a bone in the foot, producing a clicking sound as the animals walk.
Reproduction Female caribou are seasonally polyestrus, with heat intervals of 10-12 days. Mating typically occurs in October. In May or June, after a gestation of 227-229 days, a single precocious young is born. Twinning occasionally occurs in this species, but is not common. The calf, weighing 5-9 kg at birth, follows its mother within an hour of its birth, and is capable of outrunning a human by the time it is a day old.