Reindeer

Reindeer and caribou are the same species, Rangifer tarandus, a member of the deer family. The difference is mostly in the name and in how people live with them. In Europe and Asia the animal is called reindeer, and many of the reindeer there are domesticated or semi domesticated, herded by peoples such as the Sámi and the Nenets. In North America wild animals are called caribou, a word from the Mi'kmaq language, and reindeer means the domestic animals brought to Alaska from Siberia in the 1890s and their descendants. Domestic reindeer tend to be smaller, shorter legged and often paler or spotted, while wild caribou are usually taller and darker. Scientists recognize several forms, from the large woodland caribou of Canada's forests to the small, stocky Svalbard reindeer and the tundra reindeer of Siberia, and in 2022 a group of biologists proposed splitting them into several species. Reindeer are true deer, related to moose and white tailed deer.

Reindeer are medium sized deer, bigger than a white tailed deer but much smaller than a moose. They stand about 85 to 150 centimeters at the shoulder and measure 1.6 to 2.1 meters from nose to tail, and size varies a lot between regions. Males are much heavier than females. In most populations bulls weigh around 150 to 200 kilograms in autumn, and the biggest woodland caribou bulls approach 300, while cows usually weigh 80 to 120. At the other end, Svalbard reindeer are short legged and compact, and their females can weigh as little as 55 to 70 kilograms in spring. The coat changes through the year: short and brownish gray in summer, thick, long and much paler in winter, with a white neck mane in many males. The hollow outer hairs keep the animal warm and also help it float when it swims across rivers. Reindeer have a short tail, a broad furry muzzle and large hooves with long dewclaws that spread their weight on snow and soft ground.

Reindeer antlers are among the largest of any deer for the animal's body size, and they are grown and shed every year. They are made of bone, not horn. Each spring they start to grow from two bony bases on the skull, covered in a soft, hairy skin called velvet that carries blood vessels and nerves, and they grow extremely fast during the long summer days. By late summer the bone hardens, the velvet dies and the animal rubs it off against shrubs, leaving the antlers bare and often stained red or brown at first. A big bull's antlers can measure more than a meter along the beam and carry dozens of points. Their shape is distinctive: the main beams sweep back and up, and one or both brow tines grow forward over the face as a flattened shovel. Calves start growing small spikes in their first months. Shed antlers do not go to waste in the Arctic, since reindeer, rodents and other animals chew them for their calcium and other minerals.

The reindeer is the only deer in which females normally grow antlers. Not every female has them, and in some forest populations a good share have none or only small spikes, but most do. Female antlers are smaller and lighter than a bull's, and they follow a different calendar. Bulls grow their antlers in summer, fight with them during the autumn rut and drop them in November or December. Females keep theirs through the whole winter and usually shed them around the time they give birth, in May or June. The reason seems to be food. In winter, reindeer dig feeding craters in the snow to reach lichens, and a pregnant female with antlers can push away antlerless bulls and younger animals and keep her crater, which helps her and her unborn calf through the hardest months. That is why the reindeer of Christmas cards, drawn with antlers in late December, would most likely be females, or young or castrated males, which also keep their antlers longer.

Reindeer live around the top of the world, in the Arctic tundra and the boreal forest, or taiga, of North America, Europe and Asia, from sea level to about 2,000 meters. Russia and Canada hold most of the world's wild animals, Alaska has several large caribou herds and Greenland has native caribou in the west. In Europe, wild mountain reindeer survive in southern Norway, where Hardangervidda holds the largest wild herd in Europe, and Finland has a few thousand wild forest reindeer in Kainuu and Suomenselkä. About 22,000 live on Norway's Svalbard archipelago. Reindeer were brought to Iceland from Norway in the late 1700s and still roam the eastern highlands. Norwegian whalers also took them to South Georgia, where they damaged the plants and were removed in 2013 and 2014. Caribou once lived in the northern contiguous United States, but the last wild animal there was captured in 2019. Domestic reindeer are herded across northern Scandinavia, Russia and Mongolia.

Reindeer are plant eaters, and their year is ruled by food. In summer they graze on grasses, sedges, herbs, mushrooms and the fresh leaves of low shrubs such as willows and dwarf birches, building up fat before winter. Once snow covers the ground, lichens become the main food, above all the pale, branching ground lichens often called reindeer moss. Reindeer find them by smell under the snow and dig feeding holes, known as craters, with their broad, sharp hooves. Few large mammals can live on lichens, which are poor in protein but rich in carbohydrates, and reindeer manage it thanks to special microbes in their stomach. Lichens grow very slowly, so overgrazed pastures can take decades to recover. Reindeer also look for minerals: they chew shed antlers and bones, lick salty soil and in some places eat seaweed on the shore. In winter, ice layers from rain on snow can lock the lichens away completely, one of the biggest dangers they face.

Almost every part of a reindeer is adapted to the Arctic. The winter coat has a dense, woolly underfur and an outer layer of long hollow hairs that insulate so well that snow can settle on a reindeer's back without melting. Inside the nose, folded bones and a thick network of blood vessels warm and moisten the freezing air before it reaches the lungs, and recover heat and water when the animal breathes out. A 2012 study found that reindeer noses have about 25 percent more small blood vessels than human ones. The hooves change with the seasons: in summer the footpads are soft and spongy for walking on wet tundra, and in winter they shrink and tighten so the sharp rim of the hoof bites into ice. The eyes change too. Researchers in Norway found that the reflective layer at the back of the eye turns from gold in summer to deep blue in winter, which helps reindeer see in the long Arctic twilight, and they can also see ultraviolet light.

Reindeer are among the most social deer and some of the greatest travelers on land. The large tundra herds of North America and Siberia move between winter ranges in or near the forest and calving grounds and summer pastures on the open tundra, and some caribou cover more than 1,000 kilometers a year, swimming across wide rivers and lakes along the way. Not all reindeer migrate, though. Forest caribou in Canada and wild forest reindeer in Finland live in smaller groups and move much less, and Svalbard reindeer stay in the same valleys all year. Herds follow traditional routes that young animals learn from older ones. Reindeer communicate with grunts and with a clicking sound made by tendons in their feet, which may help them keep track of each other in fog and blizzards. In the autumn rut, bulls barely eat, gather groups of females and fight with their antlers. In summer, mosquitoes and botflies drive the herds onto windy ridges and snow patches for relief.

Reindeer calves are born in late spring, mostly in May and June, after a pregnancy of about seven and a half months. In migratory herds, pregnant females travel ahead to traditional calving grounds, often open tundra or high ground with fewer predators and the first green plants. Most calves in a herd are born within a few weeks of each other, so there are simply too many for wolves, bears and eagles to catch, and this synchronized birth is one of the reindeer's main defenses. A female usually has a single calf of about 4 to 8 kilograms, with a reddish brown coat. The calf can stand within an hour and follow its mother within a day, which is vital in a herd that may soon move on. Reindeer milk is very rich, with far more fat than cow's milk, and calves often double their birth weight in two weeks. They stay close to their mothers through their first winter, and in some herds many do not survive it. Females usually have their first calf at two or three years old.

The reindeer is the only deer that has been truly domesticated. Herding probably began in Siberia and northern Scandinavia around 2,000 to 3,000 years ago, and today more than 20 Arctic peoples keep domestic reindeer. In Norway, Sweden and Finland, the Sámi herd semi domesticated reindeer that roam freely for much of the year and are gathered for marking, counting and slaughter. In Russia, Nenets herders on the Yamal Peninsula still migrate with their herds over hundreds of kilometers between winter forests and summer tundra, and Evenki and other peoples herd reindeer in the Siberian taiga. In Mongolia, the Dukha, or Tsaatan, keep a few thousand reindeer in the northern taiga and ride them. Domestic reindeer provide meat, milk, hides, transport and, increasingly, tourism, with farm visits popular in Lapland and Norway in winter. Where domestic and wild reindeer meet, domestic animals can lure wild ones away or interbreed with them, a concern for Finland's wild forest reindeer.

Few animals are as woven into human culture as the reindeer. People have hunted wild reindeer since the Ice Age, when they lived as far south as France and Spain, and cave paintings and carvings from that time show them. For the Sámi of northern Scandinavia and the Kola Peninsula, reindeer herding is both a livelihood and a cultural identity centuries old, with its own vocabulary for the colors, ages and antler shapes of the animals. In North America, caribou have sustained the Inuit, the Gwich'in, the Dene, the Innu and many other First Nations, providing meat, warm hides for clothing and tents, sinew for thread and bones and antlers for tools, and the Gwich'in still call themselves the caribou people. The reindeer also holds a famous place in Christmas folklore as the animal that pulls Santa Claus's sleigh. The 1823 poem A Visit from St. Nicholas named his eight reindeer, and Rudolph was created in 1939 for a department store booklet in the United States.

The IUCN lists the reindeer as Vulnerable, and several of the biggest wild herds keep shrinking. The George River herd of Quebec and Labrador, once hundreds of thousands strong, numbered only about 8,600 caribou in 2024, about one percent of its peak. The Taimyr herd in Siberia, the largest in the world around 2000 with about a million animals, was down to roughly 240,000 in 2021, and Alaska's Western Arctic Herd fell from about 490,000 in 2003 to around 121,000. Climate change is a major cause. Warmer winters bring rain that freezes over the snow and locks away food: on the Yamal Peninsula, a rain on snow event in November 2013 killed about 61,000 domestic reindeer. Oil, gas and mining, roads, logging and overhunting add to the pressure, and in Canada boreal caribou are listed as threatened. Conservation work protects calving grounds and migration routes, limits hunting and supports Indigenous peoples in managing the herds together with governments.