A male reindeer is called a bull, according to the Smithsonian National Zoological Park. Females are referred to as cows, and babies are calves. Reindeer are domesticated in Europe, but in North America, they roam free and are called caribou.
Unlike other species of deer, both male and female reindeer, or caribou, grow antlers. Both sexes grow and shed antlers annually. As they develop, the bones are covered in "velvet," which supplies blood. LiveScience indicates that antlers grow as much as an inch a day. When fully grown, the antlers lose their velvet. In early winter, the antlers of the males drop off, while females don't lose theirs until later winter, according to the National Zoo.