Reindeer are large deer, with a thick coat that is brown during the summer, and during the winter it is gray. They have a pale-colored chest and undersides, with their rump and tail being white. Males and females both have antlers, with those of males being larger and more complex. Males usually shed them after breeding, whereas females don’t do so until spring. They have specialized hooves that will adapt in relation to the season. In summer their footpads turn spongy to give extra traction, while in winter the pads tighten and shrink to expose the edge of the hoof so they can cut into the snow and ice so that they don’t slip. They have nasal turbinate bones which serve to increase the surface area in their nostrils. Cold air can thus be warmed up by their body heat prior to entering their lungs.
Reindeer are native to the Arctic, subarctic, tundra, boreal, and mountainous regions of northern Europe, Siberia, and North America. Some populations of this species are sedentary while others perform long seasonal migrations from birthing grounds to summer and winter feeding grounds.
Reindeer travel distances that are greater than those traveled by any other terrestrial mammal. Migration leads them back to the calving grounds, and this use of traditional grounds is the way in which reindeer herds are defined. They are diurnal animals and they live in herds, the largest groups numbering tens of thousands, forming during summer months. As the cooler weather arrives, herds become smaller but the numbers will swell again during the breeding period and the fall migration. Most reindeer spend the winter in forested areas, as snow conditions here are more favorable. They can find food under the snow, presumably by being able to smell it. They use their front hooves to dig craters to reach the food. Dominant reindeer will frequently take over the craters dug by subordinate individuals.
One male will mate with multiple females, competing for females during the autumn rut, which is during October and early November. At this time, males take part in fights that leave them exhausted and injured. Dominant males control access to groups numbering 5 to 15 females. The males stop eating at this time and lose a lot of their body reserves. Gestation lasts 210 - 240 days and a single calf is produced. Within an hour of birth, calves have the ability to walk after their mother, and at one day old they are able to run fast. The young begin to be weaned at one month, when they begin to graze, occasionally suckling from their mother up until the winter, then reaching full independence. Reindeer are sexually mature at 1 - 3 years old.
Oil and mineral exploration may threaten the reindeer habitat. Humans hunt this species heavily for meat, fur and antlers.
According to the University of Michigan (Museum of Zoology), the total population size of the Reindeer is around 5 million individuals. According to the IUCN Red List, the total population size of this species is around 2,890,410 mature individuals. Specific Reindeer populations have been estimated in such areas: Alaska - 660,000 individuals; Canada - 1.3 million individuals; Greenland - around 73,430 individuals; Norway - 6,000 individuals; Finland - around 1,900 individuals; Russia - 831,500 individuals; Mongolia - fewer than 1,000 individuals. Overall, currently, reindeer are classified as Vulnerable (VU) on the IUCN Red List and its numbers today are decreasing.
Reindeer have a dramatic effect on vegetation in their range. They are important prey species for bears, wolves, and other large predators, especially during the season of calving.
Reindeer were some of the last animals that humans domesticated, considered by some to still not be fully tame. There are about 2.5 million domesticated reindeer in nine countries, with about 100,000 people tending to them, being approximately half the world’s total reindeer population. Domestication is believed to have begun between the Bronze Age and the Iron Age. Siberian owners of reindeer ride on them (Siberian reindeer being larger than those in Scandinavia). A single owner may have hundreds, sometimes thousands of animals. Fur and meat are important income sources. Towards the close of the 19th-century, people introduced reindeer into Alaska and there they interbreed with native reindeer subspecies. In Scandinavian countries reindeer meat is popular. Reindeer antlers are powdered and sold to Asian markets as an aphrodisiac, medicinal or nutritional supplement.