Reindeer

## Description

The reindeer (Rangifer tarandus), also known as the caribou in North America, is a species of deer with circumpolar distribution. Reindeer occur in both migratory and sedentary populations, and their herd sizes vary greatly in different regions. Those living in the tundra are adapted to extreme cold, and some are adapted to long-distance migration. They are unique among deer (Cervidae) in that females may have antlers, although the prevalence of antlered females varies by species and subspecies. Reindeer are the only successfully semi-domesticated deer on a large scale in the world. Both wild and domestic reindeer have been an important source of food, clothing, and shelter for Arctic people throughout history and are still herded and hunted today.

## Appearance

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.

## Distribution

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.

## Behavior

Reindeer are diurnal animals and they live in herds. During the spring migration, smaller herds will group together to form larger herds of 50,000 to 500,000 animals. During autumn migrations, the groups become smaller and the reindeer begin to mate. During winter, reindeer travel to forested areas to forage under the snow. By spring, groups leave their winter grounds to go to the calving grounds. Reindeer can swim easily and quickly, normally at about 6.5 km/h (4.0 mph) but, if necessary, at 10 km/h (6.2 mph) and migrating herds will not hesitate to swim across a large lake or broad river. Reindeer travel distances that are greater than those traveled by any other terrestrial mammal. 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 males will frequently take over the craters dug by subordinate individuals. During the Arctic summer, when there is continuous daylight, reindeer change their sleeping pattern from one synchronized with the sun to an ultradian pattern, in which they sleep when they need to digest food.

## Diet

Reindeer are herbivores (folivores, graminivores) and mainly eat lichens in winter, especially reindeer lichen. They also eat the leaves of willows and birches, as well as sedges and grasses.

## Reproduction

Reindeer are polygynous with one male mating with multiple females. The breeding season occurs 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 become reproductively mature when they are 1-3 years old.

## Population

### Population threats

One of the main threats to the reindeer is overhunting by people in some areas, which contributes to the decline of populations. Human activities, such as clear-cutting forestry practices, forest fires, and the clearing for agriculture, roadways, railways, and power lines also pose a threat to the habitat of this species. Oil and mineral exploration may also threaten the reindeer habitat. Climate change in the Arctic is another serious threat to these animals.

### Population number

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 their numbers today are decreasing.

### Ecological niche

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.

## Domestication

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, 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.

## Fun Facts

In most populations both the male and the female reindeer grow antlers. Antlers begin to grow on male reindeer in March or April and on female reindeer in May or June. This process is called antlerogenesis. As the antlers grow, they are covered in thick velvet, filled with blood vessels, and spongy in texture. The velvet that covers growing antlers is highly vascularised skin. When the antler growth is fully grown and hardened, the velvet is shed or rubbed off.

Reindeer hooves adapt to the season: in the summer, when the tundra is soft and wet, the footpads become sponge-like and provide extra traction. In the winter, the pads shrink and tighten, exposing the rim of the hoof, which cuts into the ice and crusted snow to keep reindeer from slipping. This also enables them to dig down (an activity known as "cratering") through the snow to their favorite food, a lichen known as reindeer lichen.

The knees of many subspecies of reindeer are adapted to produce a clicking sound as they walk or run. The sounds originate in the tendons of the knees and may be audible from several hundred meters away.

Reindeer can see light with wavelengths as short as 320 nm (i.e. in the ultraviolet range), considerably below the human threshold of 400 nm. It is thought that this ability helps them to survive in the Arctic, because many objects that blend into the landscape in light visible to humans, such as urine and fur, produce sharp contrasts in the ultraviolet. A specific layer of tissue in the eye of Arctic reindeer changes in color from gold in summer to blue in winter to improve their vision during times of continuous darkness, and perhaps enable them to better spot predators.

Reindeer are ruminants having a four-chambered stomach. They are the only large mammal able to metabolize lichen owing to specialized bacteria and protozoa in their gut; this is a unique adaptation among mammals.

Normally traveling about 19-55 km (12-34 mi) a day while migrating, the caribou can run at speeds of 60-80 km/h (37-50 mph). Young calves can already outrun an Olympic sprinter when only 1 day old!

Around the world, public interest in reindeer peaks in the Christmas period. According to folklore, Santa Claus's sleigh is pulled by flying reindeer through the night sky to help deliver gifts to good children on Christmas Eve.