In the fall, as white-tipped guard hairs grow out through the summer hair for extra winter insulation, caribou become a more uniform light brown. The exceptional warmth of the winter coat is the result of individual hairs which are hollow. The air cells in the hair act as an insulating layer to conserve body heat. Barren-ground caribou have the largest antlers in relation to their body size of any deer species and are the only species in which females grow antlers. Antlers are shed and regrown each year.
Calves have short spikes, but as an animal gets older, antlers increase in size and complexity.
Adult males have the largest antlers and they may be shed as early as November, just after the rut. Younger males may retain their antlers until the following April, while females lose their antlers after calving in June. For additional information see NWT Species at Risk Fact Sheets for Peary Caribou and Woodland Caribou .