The subspecies R. t. pearyi, of northern Greenland, Ellesmere Island, and nearby islands, is almost pure white. Rangifer is the only genus of the deer family in which both sexes are antlered. Although there is great diversity in the shape of the antlers, they are usually long, sweeping beams with forwardly projecting brow tines. The broad, flat, and deeply cleft hooves aid in walking on soft ground and snow. When the caribou walks, a clicking noise is produced by a tendon slipping over a bone in the foot.
Most caribou inhabit arctic tundra and surrounding boreal coniferous forest.
Some populations are found in mountainous areas farther south. Rangifer is active primarily during the day and is almost constantly on the move. Its eyesight is apparently poor, its hearing is adequate, and it depends in large part on the sense of smell to detect food and danger. Most populations have seasonal shifts in range. Those to the south may simply move to lower elevations for the winter or to areas of favorable food supplies and shelter.