Although the similarities between reindeer and caribou are numerous, the differences are enough that they are classified as two subspecies. Reindeer and caribou share the same genus, Rangifer, and species name, tarandus. Domestication is the biggest difference between reindeer and caribou. Reindeer are a semidomesticated subspecies of Rangifer, and there are many subspecies of both reindeer and caribou in Alaska.
Both male and female reindeer and caribou grow antlers -- a trait unique in the deer family -- although female reindeer antlers grow larger than female caribou antlers.
Many of the distinguishing traits are thought to be the result of domestication.
Reindeer are shorter, stouter and more sedentary than their long-legged caribou cousins, and although reindeer may migrate within their grazing range, they do not migrate long distances between wintering grounds and calving areas as caribou do.
Reindeer bulls are smaller than caribou bulls, but reindeer cows generally weigh the same as caribou cows.
Reindeer have thicker, denser fur than caribou, although both have hollow guard hairs that keep them warm.
Reindeer begin the breeding season about two to four weeks earlier than caribou, which results in reindeer calves being born at the end of April, while caribou calves are born at the end of May.
Both have hooves that can be used as snowshoes for walking on the snow and for digging.
Only in North America are wild Rangifer referred to as caribou. In Eurasia, reindeer are classified as either domesticated or wild.