Breeding takes place in August and September with calving peaking around April 24th. However, reindeer and caribou can interbreed. Most likely, breeding would be between a male caribou and female reindeer, because caribou are usually dominant. Adaptations For Life in the Arctic Pelage Reindeer hair is extremely dense. This thick coat inhibits radiation and allows them to lay on snow without melting it and getting wet.
Facial hair extends down to their lips protecting the muzzle when grazing in snow.
Reindeer don't get frost build-up from their breath. This increases the surface area inside so that blood can warm the cool incoming air. Heat is retained and moisture condensed and retained from expired air. The hollow guard hair provides bouyancy facilitating their swimming ability. However, adaptations such as preventing radiation and lack of sweat glands for heat conservation in winter may cause stress in warm weather.