Did you know that although Caribou and Reindeer are the same species of animal, the Reindeer is a bit smaller than the Caribou? In some cultures, domestic Reindeer are extremely valuable livestock animals, while in others, they are revered by children as Santa Claus's mode of transportation.

In the wild, Reindeer browse on lichens, wild mushrooms, leaves, and other vegetation. Rather than consuming large amounts of vegetation indiscriminately, Reindeer will select the most nutritious parts of the plant to eat. They often use the sharp edges of their hooves to scrape below the snow for forage. In the spring when food is very scarce, Reindeer may eat eggs and even small rodents in order to stay alive. In captivity, Reindeer will generally eat less in the winter, just like their wild relatives. They also may prefer snow to water. Reindeer are social animals and in the wild live in large herds, sometimes of up to several thousand of them. Males may not join herds; often, they may wander alone until mating season when they will begin to look for a female. During mating season, males will fight with their antlers. On occasion, the antlers of male Reindeer may stick together and the animals will not be able to separate. In these rare cases, the deer may starve if they cannot disengage their antlers. Strangely, Reindeer may be located by sound; Reindeer crackle when they walk. This is not because they step on sticks; rather, it is a physical trait of the deer itself. Its tendons actually make the noise when the Reindeer moves. After the mating season, male Reindeer shed their antlers, although females retain them. This may allow them to better defend the best feeding areas during pregnancy. Reindeer are good swimmers and have been known to use this method of transportation to move between ice floes in the Arctic Sea.

Reindeer are insulated by two special layers of hair. Long guard hairs in the coat aid the Reindeer in lying on snow. They trap the deer's heat close to its body and do not allow the animal's body heat to melt the snow, getting the animal wet. The undercoat provides extra insulation. The coat extends all the way to the Reindeer's lips to help insulate the animal's muzzle. Hair even extends under the hooves to provide traction on ice. No matter what its sex or age, each Reindeer will grow a new set of antlers every year. Occasionally some animals will not grow antlers, and the females' antlers tend to be smaller than those of the males. The ratio of body size to antler size in the Reindeer is small; they have the largest antlers of any deer. Their coats change seasonally. In the summer, the coats are fairly short, but by winter they will become lighter in color, thicker, and longer. Reindeer have hooves, which are longer and more splayed than those of deer native to climates that are more temperate. This allows them to travel more easily on snow without sinking into it, by distributing the weight of the animal over a larger surface area. Often, domestic Reindeer are lighter in color than their wild relatives. They may have white or pinto coloration over their coats, and domestic Reindeer may have flatter faces than their wild counterparts. Domestic Reindeer bulls may be a bit smaller than wild bulls, although often females are the same size. When growing new antlers, the Reindeer's antlers are covered in a material called velvet that contains lots of vascular tissue. This nourishes the antlers. When the antlers begin to harden, or turn to bone, the velvet is generally cast off in shreds. Adult male Reindeer usually weigh around 300 pounds, and females are about 100 pounds lighter. Males generally stand 43 inches at the shoulder, while females are about five inches shorter. Cow reindeer usually keep their antlers longer than bulls so the animals you see at Christmas are most likely cows, or maybe steers. Cows that are pregnant keep their antlers until the calves are born but lose them earlier (early march or so if not pregnant).

Reindeer are kept by many people for meat, food, and hides, which can be made into shelter and clothing. Their milk is very high in fat and protein. They have been domesticated for about 7,000 years in northern Eurasia and today, Reindeer have even been kept as pets. Wild Reindeer, sometimes known as Caribou, have slightly different features than domestic Reindeer. Also, wild Reindeer may scatter when chased, whereas domestic animals will herd themselves into a group. In some cultures, Santa Claus's sleigh full of Christmas gifts is drawn by a group of flying Reindeer.

Female Reindeer and calves can grow large antlers so long as they are given very good nutrition. Reindeer are so well adapted to the cold that their thick hair and lack of sweat glands may actually cause the animals to become stressed or unhealthy if they are kept in excessively warm climates. In captivity, Reindeer are usually fed on a specially formulated Reindeer food based on barley and fishmeal. This is supplemented with brome hay, molasses, vitamin and mineral supplements, and long-grass hay every few days.

Although Reindeer may become pregnant as early as five months of age, most will not breed until they are about a year old. Many will continue to calve until they are about 15. Male Reindeer generally do not breed until they are about three years of age. Generally, Reindeer breed between August and September and the young are usually born at the end of April. In the wild, calves may be preyed upon by black bears, wolves, or wolverines, and some young Reindeer may drown or die of disease.