Reindeer don't fly, but they do sometimes have red noses. These animals are part of the deer family, or Cervidae, which includes deer, elk, moose and wapiti. Like others in their family, reindeers have long legs, hooves and antlers.
Reindeer are also called caribou, depending on their location. They are called reindeer in Europe, but in North America, reindeer refers to Eurasian populations, and caribou refers to wild populations in North America, according to the San Diego Zoo. Reindeer also often refers to domesticated animals, while caribou refers to wild populations.
Some scientists think that the reindeer was one of the first domesticated animals. It was first domesticated around 2,000 years ago, according to the Smithsonian. Many Arctic societies still rely on this animal for food, clothing and materials for shelter.
Male reindeer grow to 28 to 53 inches (70 to 135 centimeters) tall from hooves to shoulder, and around 5.9 to 6.8 f (1.8 to 2.1 m) long. Females are typically smaller, around 5.5 to 6.2 feet (1.7 to 1.9 m) long. Males weigh 143 to 529 lbs. (65 to 240 kilograms), and females weigh 121 to 308 lbs. (55 to 140 kg).
These animals are the only type of deer in which both the male and female reindeers grow antlers. These antlers fall off and regrow every year. A male's can grow up to 51 inches (130 centimeters) long and weigh up to 33 lbs. (15 kg), making them very useful for fighting. A female's antlers can grow up to 20 inches (50 cm), according to the San Diego Zoo.
The secret to Rudolph's rosy schnozzle is a dense network of blood vessels in his nose, scientists explained in a 2012 Live Science article. Reindeer, it seems, have 25 percent more capillaries carrying red, oxygen-rich blood in their nasal architecture than humans, said medical researchers in the Netherlands and the University of Rochester in New York.
"In colder climates … the increase in blood flow in the nose will help keep the [nose's] surface warm," Dr. John Cullen of the University of Rochester said. The dense network of blood vessels in reindeer noses is also essential for regulating the animal's internal body temperature — like many mammals, reindeer don't sweat.
Reindeer are found in Alaska, Canada, Greenland, northern Europe and northern Asia in tundra, mountains and woodland habitats. Their home ranges tend be as big as 190 square miles (500 square km), according to Encyclopedia Britannica.
Reindeer are very social creatures. They feed, travel and rest in groups called herds. These herds can include from 10 animals to a few hundred, according to the San Diego Zoo. In the spring, herds can get even bigger — from 50,000 to 500,000 members. The herds often travel south around 1,000 miles (1,600 km) to 3,000 m (5,000 km) to find food in the winter.
Reindeer are herbivores, which means they only eat vegetation. Their diet can include herbs, ferns, mosses, grasses, shoots, fungi and leaves. On average, an adult reindeer eats around 9 to 18 lbs. (4 to 8 kg) of vegetation a day, according to the San Diego Zoo.
In the winter, reindeer must dig through the snow to find food. They dig using their antlers and munch on energy-packed lichens called reindeer moss.
Female reindeer have a gestation period of about 7.5 months and typically give birth to only one youth at a time, though they have been found to have up to four young at a time. At birth, a baby reindeer, called a calf, weighs 5 to 20 lbs. (2.5 to 9 kg).
Calves are able to stand after their first hour of life and within a week they start eating solid food in addition to their mother's milk. They are weened completely within six months and start growing their first set of antlers around their second birthday. Reindeers become mature at 4 to 6 years old and live 15 to 18 years.
Here is the classification of reindeer, according to the Integrated Taxonomic Information System (ITIS):
Species: Rangifer tarandus, and 14 subspecies
Reindeer are listed as vulnerable by the International Union for Conservation of Nature (IUCN). The IUCN's Red List of Threatened Species says the species has this distinction because it has had a 40 percent decline in population over the past 21 to 27 years. There are currently around 3.5 million caribou in North America, around 1 million wild reindeer in Eurasia and around 3 million domestic reindeer in northern Europe, according to Encyclopedia Britannica.
Male reindeer lose their antlers in November, but females keep theirs much longer. This means that Santa Claus' reindeer must have all been female, since they are depicted as having horns on December 24.
Reindeer are built for the cold. Their noses warm up air before it gets to their lungs and their entire bodies, including their hooves, are covered with fur.
These creatures can't fly, but they can run. According to the San Diego Zoo, they can run up to 50 mph (80 km/h).