The caribou, known in Eurasia as the reindeer, is an iconic Arctic mammal recognized globally for its extensive seasonal migrations across the northern tundra and boreal forests. This large member of the deer family, Rangifer tarandus, is uniquely adapted to thrive in cold, harsh environments. Its physical form is a testament to survival, featuring specialized structures that allow it to navigate snow, forage for food, and maintain warmth.
Overall Size and Body Structure
The caribou possesses a sturdy, compact build, which helps conserve body heat. Adult males, or bulls, are significantly larger than females, a difference known as sexual dimorphism. Bulls typically weigh between 125 to 300 kilograms (275 to 660 pounds), while cows range from about 68 to 136 kilograms (150 to 300 pounds). The animal stands between 85 and 140 centimeters (2 feet 9 inches to 4 feet 7 inches) tall at the shoulder. This stocky body is supported by long legs, which are built for traversing deep snow and covering vast distances during migration.
The Unique Antlers
Caribou are the sole species of deer where both males and females regularly grow antlers. Male antlers are substantially larger and more complex, sometimes exceeding 125 centimeters in length and weighing up to 9 kilograms (20 pounds). A defining element of the male’s structure is the presence of one or two large, flattened, shovel-like tines called brow tines, or palms, that project forward over the face. Antlers are true bone structures that are shed and regrown annually. During the summer growth phase, the antlers are covered in a soft, vascular skin called velvet, which supplies the necessary nutrients and blood. The timing of shedding differs notably between the sexes. Bulls drop their antlers shortly after the fall rut, typically in November or December. Pregnant females retain their smaller, more slender antlers throughout the winter, shedding them only around the time of spring calving. This allows them to effectively defend feeding sites and secure scarce winter resources.
Coat Color and Seasonal Changes
The caribou’s coat is a remarkable adaptation to its Arctic environment, providing superior insulation. The warmth comes from a double layer of fur, featuring a dense, woolly undercoat and an outer layer of longer guard hairs. These guard hairs are hollow, trapping air and creating an insulating layer that minimizes heat loss, while also providing buoyancy when the animal swims. Coat color varies significantly by season, offering camouflage throughout the year. In summer, the coat is typically a darker grayish-brown. As winter approaches, the fur grows thicker and often lightens considerably, sometimes becoming nearly white in high Arctic populations. Many caribou also possess a distinctive white patch on their neck and a prominent white ruff on the throat and chest.
Specialized Hooves and Legs
The caribou’s hooves are the most specialized feature of its locomotion. They are large, broad, and crescent-shaped, with a deep concave underside. This structure acts like a snowshoe, distributing the animal’s weight over a wider surface area to prevent sinking into soft snow or boggy tundra. The sharp edges of the hooves provide excellent traction on ice and crusty snow. These hooves are also used like a shovel to dig through snow and ice, an action called “cratering,” which allows the caribou to access buried winter food sources like lichen. In the winter, the pads of the hoof shrink and harden, while hair grows between the toes, further aiding grip.