Reindeer
The reindeer ("Rangifer tarandus"), also known as the caribou in North America, is a species of deer with circumpolar distribution, native to Arctic, subarctic, tundra, boreal, and mountainous regions of northern Europe, Siberia, and North America. This includes both sedentary and migratory populations. It is the only representative of the genus Rangifer. Herd size varies greatly in different geographic regions. "R. tarandus" varies in size and colour from the smallest subspecies, the Svalbard reindeer, to the largest, the boreal woodland caribou. The North American range of caribou extends from Alaska through the Yukon, the Northwest Territories and Nunavut into  the boreal forest and south through the Canadian Rockies. The barren-ground caribou, Porcupine caribou, and Peary caribou live in the tundra, while the shy boreal woodland caribou prefer the boreal forest. The Porcupine caribou and the barren-ground caribou form large herds and undertake lengthy seasonal migrations from birthing grounds to summer and winter feeding grounds in the tundra and taiga. The migrations of Porcupine caribou herds are among the longest of any mammal. Barren-ground caribou are also found in Kitaa in Greenland, but the larger herds are in Alaska, the Northwest Territories, and Nunavut. The Taimyr herd  of migrating Siberian tundra reindeer ("R. t. sibiricus") in Russia is the largest wild reindeer herd in the world, varying between 400,000 and 1,000,000. What was once the second largest herd is the migratory boreal woodland caribou ("R. t. caribou") George River herd in Canada, with former variations between 28,000 and 385,000. As of January 2018, there are fewer than 9,000 animals estimated to be left in the George River herd, as reported by the Canadian Broadcasting Corporation. "The New York Times" reported in April 2018 of the disappearance of the only herd of southern mountain woodland caribou in the  contiguous United States with an expert calling it "functionally extinct" after the herd's size dwindled to a mere three animals. After the last individual, a female, was translocated to a wildlife rehabilitation centre in Canada, the woodland caribou was considered extirpated from the contiguous United States. Some subspecies are rare and two have already become extinct: the Queen Charlotte Islands caribou of Canada and the East Greenland caribou from East Greenland. Historically, the range of the sedentary boreal woodland caribou covered more than half of Canada and into the northern states of the contiguous United States. Woodland caribou have  disappeared from most of their original southern range and were designated as threatened in 2002 by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Environment Canada reported in 2011 that there were approximately 34,000 boreal woodland caribou in 51 ranges remaining in Canada (Environment Canada, 2011b). Siberian tundra reindeer herds are also in decline, and "Rangifer tarandus" is considered to be vulnerable by the IUCN. Arctic peoples have depended on caribou for food, clothing, and shelter, such as the Caribou Inuit, the inland-dwelling Inuit of the Kivalliq Region in northern Canada, the Caribou Clan in the  Yukon, the Iñupiat, the Inuvialuit, the Hän, the Northern Tutchone, and the Gwichʼin (who followed the Porcupine caribou for millennia). Hunting wild reindeer and herding of semi-domesticated reindeer are important to several Arctic and subarctic peoples such as the Duhalar for meat, hides, antlers, milk, and transportation. The Sámi people (Sápmi) have also depended on reindeer herding and fishing for centuries. In Sápmi, reindeer are used to pull a pulk, a Nordic sled. Male ("bulls") and female ("cows") reindeer can grow antlers annually, although the proportion of females that grow antlers varies greatly between population and season. Antlers are  typically larger on males. In traditional United States Christmas legend, Santa Claus's reindeer pull a sleigh through the night sky to help Santa Claus deliver gifts to good children on Christmas Eve. Naming. Carl Linnaeus chose the name "Rangifer" for the reindeer genus, which Albertus Magnus used in his "De animalibus", fol. Liber 22, Cap. 268: "Dicitur Rangyfer quasi ramifer". This word may go back to the Saami word "raingo". Linnaeus chose the word "tarandus" as the specific epithet, making reference to Ulisse Aldrovandi's "Quadrupedum omnium bisulcorum historia" fol. 859–863, Cap. 30: De Tarando (1621). However, Aldrovandi and  Konrad Gesner thought that "rangifer" and "tarandus" were two separate animals. In any case, the "tarandos" name goes back to Aristotle and Theophrastus. The use of the terms "reindeer" and "caribou" for essentially the same animal can cause confusion, but the International Union for Conservation of Nature clearly delineates the issue: "The world's Caribou and Reindeer are classified as a single species "Rangifer tarandus". Reindeer is the European name for the species while in North America, the species is known as Caribou." The word "rein" is of Norse origin. The word "deer" was originally broader in meaning, but became  more specific over time. In Middle English, "der" meant a wild animal of any kind, in contrast to "cattle". The word "caribou" comes through French, from the Mi'kmaq "qalipu", meaning "snow shoveler" and referring to its habit of pawing through the snow for food. Because of its importance to many cultures, "Rangifer tarandus" and some of its subspecies have names in many languages. Inuktitut is spoken in the eastern Canadian Arctic, and the caribou is known by the name "tuktu". The Gwich'in people have over 24 distinct caribou-related words. Taxonomy and evolution. The species' taxonomic name, "Rangifer tarandus", was  defined by Carl Linnaeus in 1758. The woodland caribou subspecies' taxonomic name "Rangifer tarandus caribou" was defined by Gmelin in 1788. Based on Banfield's often-cited "A Revision of the Reindeer and Caribou, Genus Rangifer" (1961), "R. t. caboti" (the Labrador caribou), "R. t. osborni" (Osborn's caribou—from British Columbia) and "R. t. terraenovae" (the Newfoundland caribou) were considered invalid and included in "R. t. caribou". Some recent authorities have considered them all valid, even suggesting that they are quite distinct. In his chapter in the book entitled "Mammal Species of the World", English zoologist Peter Grubb agrees  with Valerius Geist, specialist on large North American mammals, that this range actually includes several subspecies. Geist (2007) argued that the "true woodland caribou, the uniformly dark, small-maned type with the frontally emphasised, flat-beamed antlers", which is "scattered thinly along the southern rim of North American caribou distribution" has been incorrectly classified. He affirms that the "true woodland caribou is very rare, in very great difficulties and requires the most urgent of attention." In 2005, an analysis of mtDNA found differences between the caribou from Newfoundland, Labrador, southwestern Canada, and southeastern Canada, but maintained all in "R. t.  caribou". Mallory and Hillis argued that "Although the taxonomic designations reflect evolutionary events, they do not appear to reflect current ecological conditions. In numerous instances, populations of the same subspecies have evolved different demographic and behavioural adaptations, while populations from separate subspecies have evolved similar demographic and behavioural patterns... "[U]nderstanding ecotype in relation to existing ecological constraints and releases may be more important than the taxonomic relationships between populations." Current classifications of "Rangifer tarandus", either with prevailing taxonomy on subspecies, designations based on ecotypes, or natural population groupings, fail to capture "the variability of caribou across their range in Canada  needed for effective species conservation and management. Across the range of a species, individuals may display considerable morphological, genetic, and behavioural variability reflective of both plasticity and adaptation to local environments." COSEWIC developed Designated Unit (DU) attribution to add to classifications already in use. Subspecies. In 2005, "Mammal Species of the World" (3rd ed.) recognised 14 subspecies, two of which are extinct. The table above includes "R. t. caboti" (the Labrador caribou), "R. t. osborni" (Osborn's caribou – from British Columbia) and "R. t. terraenovae" (the Newfoundland caribou). Based on a review in 1961, these were considered invalid and included  in "R. t. caribou", but some recent authorities have considered them all valid, even suggesting that they are quite distinct. An analysis of mtDNA in 2005 found differences between the caribou from Newfoundland, Labrador, southwestern Canada and southeastern Canada, but maintained all in "R. t. caribou". There are seven subspecies of reindeer in Eurasia, of which only two are found in Fennoscandia: the mountain reindeer ("R. t. tarandus") in Norway, Sweden, Finland, and Russia and the Finnish forest reindeer ("R. t. fennicus") in Finland and Russia. Two subspecies are found only in North America: the Porcupine caribou ("R. t. granti ) and the Peary caribou (R. t. pearyi"). The barren-ground caribou ("R. t. groenlandicus") is found in western Greenland, but the larger herds are in Alaska, the Northwest Territories and Nunavut. According to Grubb, based on Banfield and considerably modified by Geist, these subspecies and divisions are considered valid: the "caribou" or woodland caribou division, which includes "R. t. buskensis", "R. t. caribou", "R. t. dawsoni", "R. t. fennicus", "R. t. phylarchus" and "R. t. valentinae" ("R. t. osborni" is a transitional subspecies between the "caribou" and "tarandus" divisions), the "tarandus" or tundra reindeer division, which includes "R. t. caboti , R. t. groenlandicus", "R. t. pearsoni", "R. t. sibiricus" and "R. t. terraenovae" and the "platyrhynchus" or dwarf reindeer division, which includes "R. t. pearyi" and "R. t. platyrhynchus". Some of the "Rangifer tarandus" subspecies may be further divided by ecotype depending on several behavioural factors – predominant habitat use (northern, tundra, mountain, forest, boreal forest, forest-dwelling, woodland, woodland (boreal), woodland (migratory) or woodland (mountain), spacing (dispersed or aggregated) and migration patterns (sedentary or migratory). The "glacial-interglacial cycles of the upper Pleistocene had a major influence on the evolution" of "Rangifer tarandus" and other Arctic and subarctic species. Isolation  of "Rangifer tarandus" in refugia during the last glacial – the Wisconsin in North America and the Weichselian in Eurasia-shaped "intraspecific genetic variability" particularly between the North American and Eurasian parts of the Arctic. In 1986, Kurtén reported that the oldest reindeer fossil was an "antler of tundra reindeer type from the sands of Süssenborn" in the Pleistocene (Günz) period (680,000 to 620,000 BP). By the 4-Würm period (110,000–70,000 to 12,000–10,000 BP) its European range was very extensive. Reindeer occurred in "In spite of the great variation, all the Pleistocene and living reindeer belong to the same species." Humans  started hunting reindeer in the Mesolithic and Neolithic periods and humans are today the main predator in many areas. Norway and Greenland have unbroken traditions of hunting wild reindeer from the last glacial period until the present day. In the non-forested mountains of central Norway, such as Jotunheimen, it is still possible to find remains of stone-built trapping pits, guiding fences and bow rests, built especially for hunting reindeer. These can, with some certainty, be dated to the Migration Period, although it is not unlikely that they have been in use since the Stone Age. Physical characteristics. Antlers . In most cervid species, only males grow antlers; the reindeer is the only cervid species in which females also grow them normally. Androgens play an essential role in the antler formation of cervids. The antlerogenic genes in reindeer have more sensitivity to androgens in comparison with other cervids. There is considerable variation between subspecies in the size of the antlers (e.g., they are rather small and spindly in the northernmost subspecies), but on average the bull's antlers are the second largest of any extant deer, after those of the male moose. In the largest subspecies, the antlers of large  bulls can range up to in width and in beam length. They have the largest antlers relative to body size among living deer species. Antler size measured in number of points reflects the nutritional status of the reindeer and climate variation of its environment. The number of points on male reindeer increases from birth to five years of age and remains relatively constant from then on. "In male caribou, antler mass (but not the number of tines) varies in concert with body mass." While antlers of male woodland caribou are typically smaller than those of male barren-ground caribou, they  can be over across. They are flattened, compact and relatively dense. Geist describes them as frontally emphasised, flat-beamed antlers. Woodland caribou antlers are thicker and broader than those of the barren-ground caribou and their legs and heads are longer. Quebec-Labrador male caribou antlers can be significantly larger and wider than other woodland caribou. Central barren-ground male caribou antlers are perhaps the most diverse in configuration and can grow to be very high and wide. Mountain caribou antlers are typically the most massive, with the largest circumference measurements. The antlers' main beams begin at the brow "extending  posterior over the shoulders and bowing so that the tips point forward. The prominent, palmate brow tines extend forward, over the face." The antlers typically have two separate groups of points, lower and upper. Antlers begin to grow on male reindeer in March or April and on female reindeer in May or June. This process is called antlerogenesis. Antlers grow very quickly every year on the bulls. As the antlers grow, they are covered in thick velvet, filled with blood vessels and spongy in texture. The antler velvet of the barren-ground caribou and the boreal woodland caribou is dark  chocolate brown. The velvet that covers growing antlers is a highly vascularised skin. This velvet is dark brown on woodland or barren-ground caribou and slate-grey on Peary caribou and the Dolphin-Union caribou herd. Velvet lumps in March can develop into a rack measuring more than a metre in length by August. When the antler growth is fully grown and hardened, the velvet is shed or rubbed off. To the Inuit, for whom the caribou is a "culturally important keystone species", the months are named after landmarks in the caribou life cycle. For example, "amiraijaut" in the Igloolik  region is "when velvet falls off caribou antlers." Male reindeer use their antlers to compete with other males during the mating season. In describing woodland caribou, SARA wrote, "During the rut, males engage in frequent and furious sparring battles with their antlers. Large males with large antlers do most of the mating." Reindeer continue to migrate until the bulls have spent their back fat. In late autumn or early winter after the rut, male reindeer lose their antlers, growing a new pair the next summer with a larger rack than the previous year. Female reindeer keep their antlers until they  calve. In the Scandinavian and Arctic Circle populations, old bulls' antlers fall off in late December, young bulls' antlers fall off in the early spring, and cows' antlers fall off in the summer. When male reindeer shed their antlers in early to midwinter, the antlered cows acquire the highest ranks in the feeding hierarchy, gaining access to the best forage areas. These cows are healthier than those without antlers. Calves whose mothers do not have antlers are more prone to disease and have a significantly higher mortality. Cows in good nutritional condition, for example, during a mild winter with good  winter range quality, may grow new antlers earlier as antler growth requires high intake. According to a respected Igloolik elder, Noah Piugaattuk, who was one of the last outpost camp leaders, caribou ("tuktu") antlers According to the "Igloolik Oral History Project" (IOHP), "Caribou antlers provided the Inuit with a myriad of implements, from snow knives and shovels to drying racks and seal-hunting tools. A complex set of terms describes each part of the antler and relates it to its various uses". Currently, the larger racks of antlers are used by Inuit as materials for carving. Iqaluit-based Jackoposie Oopakak 's 1989 carving, entitled "Nunali", which means ""place where people live", and which is part of the permanent collection of the National Gallery of Canada, includes a massive set of caribou antlers on which he has intricately carved the miniaturised world of the Inuit where "Arctic birds, caribou, polar bears, seals, and whales are interspersed with human activities of fishing, hunting, cleaning skins, stretching boots, and travelling by dog sled and kayak...from the base of the antlers to the tip of each branch". Pelt. The colour of the fur varies considerably, both between individuals and depending on season and  subspecies. Northern populations, which usually are relatively small, are whiter, while southern populations, which typically are relatively large, are darker. This can be seen well in North America, where the northernmost subspecies, the Peary caribou, is the whitest and smallest subspecies of the continent, while the southernmost subspecies, the boreal woodland caribou, is the darkest and largest. The coat has two layers of fur: a dense woolly undercoat and longer-haired overcoat consisting of hollow, air-filled hairs. Fur is the primary insulation factor that allows reindeer to regulate their core body temperature in relation to their environment, the thermogradient , even if the temperature rises to . In 1913, Dugmore noted how the woodland caribou swim so high out of the water, unlike any other mammal, because their hollow, "air-filled, quill-like hair" acts as a supporting "life jacket." A darker belly colour may be caused by two mutations of MC1R. They appear to be more common in domestic reindeer herds. Heat exchange. Blood moving into the legs is cooled by blood returning to the body in a countercurrent heat exchange (CCHE), a highly efficient means of minimising heat loss through the skin's surface. In the CCHE mechanism, in  cold weather, blood vessels are closely knotted and intertwined with arteries to the skin and appendages that carry warm blood with veins returning to the body that carry cold blood causing the warm arterial blood to exchange heat with the cold venous blood. In this way, their legs for example are kept cool, maintaining the core body temperature nearly higher with less heat lost to the environment. Heat is thus recycled instead of being dissipated. The "heart does not have to pump blood as rapidly in order to maintain a constant body core temperature and thus, metabolic rate." CCHE is  present in animals like reindeer, fox and moose living in extreme conditions of cold or hot weather as a mechanism for retaining the heat in (or out of) the body. These are countercurrent exchange systems with the same fluid, usually blood, in a circuit, used for both directions of flow. Reindeer have specialised counter-current vascular heat exchange in their nasal passages. Temperature gradient along the nasal mucosa is under physiological control. Incoming cold air is warmed by body heat before entering the lungs and water is condensed from the expired air and captured before the reindeer's breath is  exhaled, then used to moisten dry incoming air and possibly be absorbed into the blood through the mucous membranes. Like moose, caribou have specialised noses featuring nasal turbinate bones that dramatically increase the surface area within the nostrils. Hooves. The reindeer has large feet with crescent-shaped cloven hooves for walking in snow or swamps. According to the Species at Risk Public Registry (SARA), woodland 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 it from slipping. This also enables them to dig down (an activity known as "cratering") through the snow to their favourite food, a lichen known as reindeer lichen ("Cladonia rangiferina"). Size. The females (or "cows" as they are often called) usually measure in length and weigh . The males (or "bulls" as they are often called) are typically larger (to an extent which varies between the different subspecies), measuring in length and usually weighing . Exceptionally large bulls have weighed as much as . Weight varies drastically between the  seasons, with bulls losing as much as 40% of their pre-rut weight. The shoulder height is usually , and the tail is long. The reindeer from Svalbard are the smallest of all. They are also relatively short-legged and may have a shoulder height of as little as , thereby following Allen's rule. Clicking sound. The knees of many subspecies of reindeer are adapted to produce a clicking sound as they walk. The sounds originate in the tendons of the knees and may be audible from several hundred metres away. The frequency of the knee-clicks is one of a  range of signals that establish relative positions on a dominance scale among reindeer. "Specifically, loud knee-clicking is discovered to be an honest signal of body size, providing an exceptional example of the potential for non-vocal acoustic communication in mammals." The clicking sound made by reindeer as they walk is caused by small tendons slipping over bone protuberances (sesamoid bones) in their feet. The sound is made when a reindeer is walking or running, occurring when the full weight of the foot is on the ground or just after it is relieved of the weight. Eyes. A study by  researchers from University College London in 2011 revealed that 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 ultraviolet. The tapetum lucidum of Arctic reindeer eyes changes in colour 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. Biology and behaviours. Seasonal body composition. Reindeer have developed adaptations for optimal metabolic efficiency during warm months as well as for during cold months. The body composition of reindeer varies highly with the seasons. Of particular interest is the body composition and diet of breeding and non-breeding females between the seasons. Breeding females have more body mass than non-breeding females between the months of March and September with a difference of around more than non-breeding females. From November to December, non-breeding females have more body mass than breeding females, as non-breeding  females are able to focus their energies towards storage during colder months rather than lactation and reproduction. Body masses of both breeding and non-breeding females peaks in September. During the months of March through April, breeding females have more fat mass than the non-breeding females with a difference of almost . After this, however, non-breeding females on average have a higher body fat mass than do breeding females. The environmental variations play a large part in reindeer nutrition, as winter nutrition is crucial to adult and neonatal survival rates. Lichens are a staple during the winter months as  they are a readily available food source, which reduces the reliance on stored body reserves. Lichens are a crucial part of the reindeer diet; however, they are less prevalent in the diet of pregnant reindeer compared to non-pregnant individuals. The amount of lichen in a diet is found more in non-pregnant adult diets than pregnant individuals due to the lack of nutritional value. Although lichens are high in carbohydrates, they are lacking in essential proteins that vascular plants provide. The amount of lichen in a diet decreases in latitude, which results in nutritional stress being higher in areas  with low lichen abundance. Reproduction and life cycle. Reindeer mate in late September to early November and the gestation period is about 228–234 days. During the mating season, bulls battle for access to cows. Two bulls will lock each other's antlers together and try to push each other away. The most dominant bulls can collect as many as 15–20 cows to mate with. A bull will stop eating during this time and lose much of his body fat reserves. To calve, "females travel to isolated, relatively predator-free areas such as islands in lakes, peatlands, lake-shores, or tundra ." As females select the habitat for the birth of their calves, they are warier than males. Dugmore noted that, in their seasonal migrations, the herd follows a female for that reason. Newborns weigh on average . In May or June, the calves are born. After 45 days, the calves are able to graze and forage, but continue suckling until the following autumn when they become independent from their mothers. Bulls live four years less than the cows, whose maximum longevity is about 17 years. Cows with a normal body size and who have had sufficient summer nutrition can begin breeding anytime  between the ages of 1 to 3 years. When a cow has undergone nutritional stress, it is possible for her to not reproduce for the year. Dominant bulls, those with larger body size and antler racks, inseminate more than one cow a season. Social structure, migration and range. Some populations of North American caribou, for example many herds in the barren-ground caribou subspecies and some woodland caribou in Ungava and Labrador, migrate the farthest of any terrestrial mammal, travelling up to a year, and covering . Other North American populations, the boreal woodland caribou for example, are largely sedentary. The  European populations are known to have shorter migrations. Island herds, such as the subspecies "R. t. pearsoni" and "R. t. platyrhynchus", make local movements. Migrating reindeer can be negatively affected by parasite loads. Severely infected individuals are weak and probably have shortened lifespans, but parasite levels vary between populations. Infections create an effect known as culling: infected migrating animals are less likely to complete the migration. Normally travelling about a day while migrating, the caribou can run at speeds of . Young calves can already outrun an Olympic sprinter when only 1 day old. During the spring migration, smaller herds will  group together to form larger herds of 50,000 to 500,000 animals, but 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. A reindeer can swim easily and quickly, normally at about but, if necessary, at and migrating herds will not hesitate to swim across a large lake or broad river. As an adaptation to their Arctic environment, they have lost their circadian rhythm. Ecology. Distribution and habitat. Originally, the reindeer was  found in Scandinavia, Eastern Europe, Greenland, Russia, Mongolia and northern China north of the 50th latitude. In North America, it was found in Canada, Alaska, and the northern conterminous United States from Washington to Maine. In the 19th century, it was still present in southern Idaho. Even in historical times, it probably occurred naturally in Ireland, and it is believed to have lived in Scotland until the 12th century, when the last reindeer were hunted in Orkney. During the Late Pleistocene epoch, reindeer occurred further south, such as in Nevada, Tennessee, and Alabama in North America and as far south  as Spain in Europe. Today, wild reindeer have disappeared from these areas, especially from the southern parts, where it vanished almost everywhere. Large populations of wild reindeer are still found in Norway, Finland, Siberia, Greenland, Alaska and Canada. According to Grubb (2005), "Rangifer tarandus" is "circumboreal in the tundra and taiga" from "Svalbard, Norway, Finland, Russia, Alaska (USA) and Canada including most Arctic islands, and Greenland, south to northern Mongolia, China (Inner Mongolia), Sakhalin Island, and USA (northern Idaho and Great Lakes region)." Reindeer were introduced to, and are feral in, "Iceland, Kerguelen Islands, South Georgia Island, Pribilof Islands, St.  Matthew Island"; a free-ranging semi-domesticated herd is also present in Scotland. There is strong regional variation in "Rangifer" herd size. There are large population differences among individual herds and the size of individual herds has varied greatly since 1970. The largest of all herds (in Taimyr, Russia) has varied between 400,000 and 1,000,000; the second largest herd (at the George River in Canada) has varied between 28,000 and 385,000. While "Rangifer" is a widespread and numerous genus in the northern Holarctic, being present in both tundra and taiga (boreal forest), by 2013, many herds had "unusually low numbers  and their winter ranges in particular were smaller than they used to be. Caribou and reindeer numbers have fluctuated historically, but many herds are in decline across their range. This global decline is linked to climate change for northern migratory herds and industrial disturbance of habitat for non-migratory herds. Barren-ground caribou are susceptible to the effects of climate change due to a mismatch in the phenological process, between the availability of food during the calving period. Diet. Reindeer are ruminants, having a four-chambered stomach. They mainly eat lichens in winter, especially reindeer lichen (Cladonia rangiferina"); they are  the only large mammal able to metabolise lichen owing to specialised bacteria and protozoa in their gut. They are also the only animals (except for some gastropods) in which the enzyme lichenase, which breaks down lichenin to glucose, has been found. However, they also eat the leaves of willows and birches, as well as sedges and grasses. Reindeer are osteophagous, they are known to gnaw and partly consume shed antlers as a dietary supplement and in some extreme cases will cannibalise each other's antlers before shedding. There is also some evidence to suggest that on occasion, especially in the  spring when they are nutritionally stressed, they will feed on small rodents (such as lemmings), fish (such as Arctic char), and bird eggs. Reindeer herded by the Chukchis have been known to devour mushrooms enthusiastically in late summer. During the Arctic summer, when there is continuous daylight, reindeer change their sleeping pattern from one synchronised with the sun to an ultradian pattern, in which they sleep when they need to digest food. Predators. A variety of predators prey heavily on reindeer, including overhunting by people in some areas, which contributes to the decline of populations. Golden eagles prey on calves  and are the most prolific hunter on the calving grounds. Wolverines will take newborn calves or birthing cows, as well as (less commonly) infirm adults. Brown bears and polar bears prey on reindeer of all ages but, like wolverines, they are most likely to attack weaker animals, such as calves and sick reindeer, since healthy adult reindeer can usually outpace a bear. The grey wolf is the most effective natural predator of adult reindeer and sometimes takes large numbers, especially during the winter. Some wolf packs, as well as individual grizzly bears in Canada, may follow and live off of  a particular reindeer herd year-round. In 2020, scientists on Svalbard witnessed, and were able to film for the first time, a polar bear attack reindeer, driving one into the ocean, where the polar bear caught up with and killed it.<ref name="Chapman_10/22/2021"></ref> The same bear successfully repeated this hunting technique the next day. On Svalbard, reindeer remains account for 27.3% in polar bear scats, suggesting they "may be a significant part of the polar bear's diet in that area".<ref name="Stempniewicz_Kulaszewicz_Aars_10/12/2021"></ref> Additionally, as carrion, reindeer may be scavenged opportunistically by foxes, hawks and ravens. Bloodsucking insects, such as  mosquitoes, black flies, the reindeer warble fly or reindeer botfly ("Hypoderma tarandi") and the reindeer nose botfly ("Cephenemyia trompe"), are a plague to reindeer during the summer and can cause enough stress to inhibit feeding and calving behaviours. An adult reindeer will lose perhaps about of blood to biting insects for every week it spends in the tundra. The population numbers of some of these predators is influenced by the migration of reindeer. Tormenting insects keep caribou on the move, searching for windy areas like hilltops and mountain ridges, rock reefs, lakeshore and forest openings, or snow patches that offer  respite from the buzzing horde. Gathering in large herds is another strategy that caribou use to block insects. Reindeer are good swimmers, and in one case, the entire body of a reindeer was found in the stomach of a Greenland shark ("Somniosus microcephalus"), a species found in the far northern Atlantic. Other threats. White-tailed deer ("Odocoileus virginianus") commonly carry meningeal worm or brainworm, a nematode parasite that causes reindeer, moose ("Alces alces"), elk ("Cervus canadensis"), and mule deer ("Odocoileus hemionus") to develop fatal neurological symptoms which include a loss of fear of humans. White-tailed deer that carry this  worm are partly immune to it. Changes in climate and habitat beginning in the 20th century have expanded range overlap between white-tailed deer and caribou, increasing the frequency of infection within the reindeer population. This increase in infection is a concern for wildlife managers. Human activities, such as "clear-cutting forestry practices, forest fires, and the clearing for agriculture, roadways, railways, and power lines," favour the conversion of habitats into the preferred habitat of the white-tailed deer – "open forest interspersed with meadows, clearings, grasslands, and riparian flatlands." Towards the end of the Soviet Union, there was increasingly open  admission from the Soviet government that reindeer numbers were being negatively affected by human activity, and that this must be remediated especially by supporting reindeer breeding by native herders. Conservation. Current status. While overall widespread and numerous, some reindeer subspecies are rare and two have already become extinct. As of 2015, the IUCN has classified the reindeer as Vulnerable due to an observed population decline of 40% over the last +25 years. According to IUCN, "Rangifer tarandus" as a species is not endangered because of its overall large population and its widespread range. In North America, "R. t. dawsoni" and  R. t. eogroenlandicus are extinct, "R. t. pearyi" is endangered, "R. t. caribou" is designated as threatened and some individual populations are endangered. While the subspecies "R. t. granti" and "R. t. groenlandicus" are not designated as threatened, many individual herds — including some of the largest — are declining and there is much concern at the local level. "Rangifer tarandus" is endangered in Canada in regions such as southeastern British Columbia at the Canada–United States border, along the Columbia, Kootenay and Kootenai Rivers and around Kootenay Lake. "Rangifer tarandus" is now considered extirpated in the contiguous United States, including Idaho  and Washington. There is strong regional variation in "Rangifer" herd size. By 2013, many caribou herds in North America had "unusually low numbers" and their winter ranges in particular were smaller than they used to be. Caribou numbers have fluctuated historically, but many herds are in decline across their range. There are many factors contributing to the decline in numbers. Boreal woodland caribou (COSEWIC designation as threatened). Ongoing human development of their habitat has caused populations of woodland caribou to disappear from their original southern range. In particular, caribou were extirpated in many areas of eastern North America in the  beginning of the 20th century. Woodland caribou were designated as threatened in 2002. Environment Canada reported in 2011 that there were approximately 34,000 boreal woodland caribou in 51 ranges remaining in Canada (Environment Canada, 2011b). Professor Marco Musiani of the University of Calgary said in a statement that "The woodland caribou is already an endangered species in southern Canada and the United States...[The] warming of the planet means the disappearance of their critical habitat in these regions. Caribou need undisturbed lichen-rich environments and these types of habitats are disappearing." Woodland caribou have disappeared from most of their original  southern range and were designated as threatened in 2002 by the Committee on the Status of Endangered Wildlife in Canada, (COSEWIC). Environment Canada reported in 2011 that there were approximately 34 000 boreal woodland caribou in 51 ranges remaining in Canada.(Environment Canada, 2011b). "According to Geist, the "woodland caribou is highly endangered throughout its distribution right into Ontario." In 2002 the Atlantic-Gaspésie population of the woodland caribou was designated as endangered by COSEWIC. The small isolated population of 200 animals was at risk from predation and habitat loss. Peary caribou (COSEWIC designation as endangered). In 1991 COSEWIC assigned "endangered  status" to the Banks Island and High Arctic populations of Peary caribou. The Low Arctic population of Peary caribou was designated as threatened. By 2004 all three were designated as "endangered." Relationship with humans. The reindeer has an important economic role for all circumpolar peoples, including the Sámi, the Swedes, the Norwegians, the Finns and the Northwestern Russians in Europe, the Nenets, the Khanty, the Evenks, the Yukaghirs, the Chukchi and the Koryaks in Asia and the Inuit in North America. It is believed that domestication started between the Bronze and Iron Ages. Siberian reindeer owners also use the reindeer  to ride on (Siberian reindeer are larger than their Scandinavian relatives). For breeders, a single owner may own hundreds or even thousands of animals. The numbers of Russian and Scandinavian reindeer herders have been drastically reduced since 1990. The sale of fur and meat is an important source of income. Reindeer were introduced into Alaska near the end of the 19th century; they interbred with the native caribou subspecies there. Reindeer herders on the Seward Peninsula have experienced significant losses to their herds from animals (such as wolves) following the wild caribou during their migrations. Reindeer meat is popular in  the Scandinavian countries. Reindeer meatballs are sold canned. Sautéed reindeer is the best-known dish in Sápmi. In Alaska and Finland, reindeer sausage is sold in supermarkets and grocery stores. Reindeer meat is very tender and lean. It can be prepared fresh, but also dried, salted and hot- and cold-smoked. In addition to meat, almost all of the internal organs of reindeer can be eaten, some being traditional dishes. Furthermore, "Lapin Poron liha", fresh reindeer meat completely produced and packed in Finnish Sápmi, is protected in Europe with PDO classification. Reindeer antlers are powdered and sold as an aphrodisiac , or as a nutritional or medicinal supplement, to Asian markets. The blood of the caribou was supposedly mixed with alcohol as drink by hunters and loggers in colonial Quebec to counter the cold. This drink is now enjoyed without the blood as a wine and whiskey drink known as "Caribou". Indigenous North Americans. Caribou are still hunted in Greenland and in North America. In the traditional lifestyles of some of Canada's Inuit peoples and northern First Nations peoples, Alaska Natives, and the Kalaallit of Greenland, caribou is an important source of food, clothing, shelter and tools. The Caribou Inuit  are inland-dwelling Inuit in present-day Nunavut's Kivalliq Region (formerly the Keewatin Region, Northwest Territories), Canada. They subsisted on caribou year-round, eating dried caribou meat in the winter. The Ihalmiut are Caribou Inuit that followed the Qamanirjuaq barren-ground caribou herd. There is an Inuit saying in the Kivalliq Region: Elder Chief of Koyukuk and chair for the Western Arctic Caribou Herd Working Group Benedict Jones, or Kʼughtoʼoodenoolʼoʼ, represents the Middle Yukon River, Alaska. His grandmother was a member of the Caribou Clan, who travelled with the caribou as a means to survive. In 1939, they were  living their traditional lifestyle at one of their hunting camps in Koyukuk near the location of what is now the Koyukuk National Wildlife Refuge. His grandmother made a pair of new mukluks in one day. Kʼughtoʼoodenoolʼoʼ recounted a story told by an elder, who "worked on the steamboats during the gold rush days out on the Yukon." In late August, the caribou migrated from the Alaska Range up north to Huslia, Koyukuk and the Tanana area. One year when the steamboat was unable to continue, they ran into a caribou herd estimated to number 1 million animals, migrating across the  Yukon. "They tied up for seven days waiting for the caribou to cross. They ran out of wood for the steamboats, and had to go back down 40 miles to the wood pile to pick up some more wood. On the tenth day, they came back and they said there was still caribou going across the river night and day." The Gwich'in, an indigenous people of northwestern Canada and northeastern Alaska, have been dependent on the international migratory Porcupine caribou herd for millennia. To them caribou — "vadzaih" — is the cultural symbol and a keystone subsistence species of the Gwich'in, just  as the buffalo is to the Plains Indians. Innovative language revitalisation projects are underway to document the language and to enhance the writing and translation skills of younger Gwich'in speakers. In one project, lead research associate and fluent speaker Gwich'in elder Kenneth Frank works with linguists who include young Gwich'in speakers affiliated with the Alaska Native Language Center at the University of Alaska in Fairbanks to document traditional knowledge of caribou anatomy. The main goal of the research was to "elicit not only what the Gwich'in know about caribou anatomy, but how they see caribou and what they say and  believe about caribou that defines themselves, their dietary and nutritional needs, and their subsistence way of life." Elders have identified at least 150 descriptive Gwich'in names for all of the bones, organs and tissues. Associated with the caribou's anatomy are not just descriptive Gwich'in names for all of the body parts, including bones, organs, and tissues, but also "an encyclopedia of stories, songs, games, toys, ceremonies, traditional tools, skin clothing, personal names and surnames, and a highly developed ethnic cuisine." In the 1980s, Gwich'in Traditional Management Practices were established to protect the Porcupine caribou, upon which the Gwich'in people  depend. They "codified traditional principles of caribou management into tribal law" which include "limits on the harvest of caribou and procedures to be followed in processing and transporting caribou meat" and limits on the number of caribou to be taken per hunting trip. Indigenous Eurasians. Reindeer herding has been vital for the subsistence of several Eurasian nomadic indigenous peoples living in the circumpolar Arctic zone such as the Sámi, Nenets, and Komi. Reindeer are used to provide renewable sources and reliable transportation. In Mongolia, the Dukha are known as the reindeer people. They are credited as one of the world 's earliest domesticators. The Dukha diet consists mainly of reindeer dairy products. Reindeer husbandry is common in Fennoscandia (Norway, Sweden, Finland, and the northwestern Russian region). In Norway and Sweden, reindeer ownership is restricted to the Sámi people. In some human groups such as the Eveny, wild reindeer and domesticated reindeer are treated as different kinds of beings. Husbandry. The reindeer is the only successfully semi-domesticated deer on a large scale in the world. Reindeer in northern Fennoscandia (northern Norway, Sweden and Finland) as well in the Kola Peninsula and Yakutia in Russia, are all semi-wild domestic reindeer  ("Rangifer tarandus" forma "domesticus"), ear-marked by their owners. Some reindeer in the area are truly domesticated, mostly used as draught animals (nowadays commonly for tourist entertainment and races, traditionally important for the nomadic Sámi). Domesticated reindeer have also been used for milk, e.g., in Norway. There are only two genetically pure populations of wild reindeer in Northern Europe: wild mountain reindeer ("Rangifer tarandus tarandus") that live in central Norway, with a population in 2007 of between 6,000 and 8,400 animals; and wild Finnish forest reindeer ("Rangifer tarandus fennicus") that live in central and eastern Finland and in Russian Karelia , with a population of about 4,350, plus 1,500 in Arkhangelsk and 2,500 in Komi. DNA analysis indicates that reindeer were independently domesticated in Fennoscandia and Western Russia (and possibly Eastern Russia). Reindeer have been herded for centuries by several Arctic and subarctic peoples, including the Sámi, the Nenets and the Yakuts. They are raised for their meat, hides and antlers and, to a lesser extent, for milk and transportation. Reindeer are not considered fully domesticated, as they generally roam free on pasture grounds. In traditional nomadic herding, reindeer herders migrate with their herds between coastal and inland areas according to  an annual migration route and herds are keenly tended. However, reindeer were not bred in captivity, though they were tamed for milking as well as for use as draught animals or beasts of burden. Domesticated reindeer are shorter-legged and heavier than their wild counterparts. In Scandinavia, management of reindeer herds is primarily conducted through "siida", a traditional Sámi form of cooperative association. The use of reindeer for transportation is common among the nomadic peoples of northern Russia (but not anymore in Scandinavia). Although a sled drawn by 20 reindeer will cover no more than a day (compared to on  foot, by a dog sled loaded with cargo and by a dog sled without cargo), it has the advantage that the reindeer will discover their own food, while a pack of 5–7 sled dogs requires of fresh fish a day. The use of reindeer as semi-domesticated livestock in Alaska was introduced in the late 19th century by the United States Revenue Cutter Service, with assistance from Sheldon Jackson, as a means of providing a livelihood for Alaska Natives. Reindeer were imported first from Siberia and later also from Norway. A regular mail run in Wales, Alaska, used a sleigh  drawn by reindeer. In Alaska, reindeer herders use satellite telemetry to track their herds, using online maps and databases to chart the herd's progress. Domesticated reindeer are mostly found in northern Fennoscandia and Russia, with a herd of approximately 150–170 reindeer living around the Cairngorms region in Scotland. The last remaining wild tundra reindeer in Europe are found in portions of southern Norway. The International Centre for Reindeer Husbandry (ICR), a circumpolar organisation, was established in 2005 by the Norwegian government. ICR represents over 20 indigenous reindeer peoples and about 100,000 reindeer herders in nine different national states. In  Finland, there are about 6,000 reindeer herders, most of whom keep small herds of less than 50 reindeer to raise additional income. With 185,000 reindeer (), the industry produces of reindeer meat and generates 35 million euros annually. 70% of the meat is sold to slaughterhouses. Reindeer herders are eligible for national and EU agricultural subsidies, which constituted 15% of their income. Reindeer herding is of central importance for the local economies of small communities in sparsely populated rural Sápmi. Currently, many reindeer herders are heavily dependent on diesel fuel to provide for electric generators and snowmobile transportation, although solar photovoltaic  systems can be used to reduce diesel dependency. History. Reindeer hunting by humans has a very long history and wild reindeer "may well be the species of single greatest importance in the entire anthropological literature on hunting." Both Aristotle and Theophrastus have short accounts – probably based on the same source – of an ox-sized deer species, named "tarandos", living in the land of the Bodines in Scythia, which was able to change the colour of its fur to obtain camouflage. The latter is probably a misunderstanding of the seasonal change in reindeer fur colour. The descriptions have been interpreted as  being of reindeer living in the southern Ural Mountains in c. 350 BC. A deer-like animal described by Julius Caesar in his "Commentarii de Bello Gallico" (chapter 6.26) from the Hercynian Forest in the year 53 BC is most certainly to be interpreted as a reindeer: According to Olaus Magnus's "Historia de Gentibus Septentrionalibus" – printed in Rome in the year 1555 – Gustav I of Sweden sent 10 reindeer to Albert I, Duke of Prussia, in the year 1533. It may be these animals that Conrad Gessner had seen or heard of. During World War II, the Soviet Army  used reindeer as pack animals to transport food, ammunition and post from Murmansk to the Karelian front and bring wounded soldiers, pilots and equipment back to the base. About 6,000 reindeer and more than 1,000 reindeer herders were part of the operation. Most herders were Nenets, who were mobilised from the Nenets Autonomous Okrug, but reindeer herders from Murmansk, Arkhangelsk and Komi also participated. Santa Claus. Around the world, public interest in reindeer peaks in the Christmas period. According to folklore, Santa Claus's sleigh is pulled by flying reindeer. These reindeer were first named in the 1823 poem "A  Visit from St. Nicholas". Mythology and art. Among the Inuit, there is a story of the origin of the caribou: Inuit artists from the barren lands, incorporate depictions of caribou — and items made from caribou antlers and skin — in carvings, drawings, prints and sculpture. Contemporary Canadian artist Brian Jungen, of Dunne-za First Nations ancestry, commissioned an installation entitled "The ghosts on top of my head" (2010–11) in Banff, Alberta, which depicts the antlers of caribou, elk and moose. Tomson Highway, CM is a Canadian and Cree playwright, novelist, and children's author, who was born in a remote area  north of Brochet, Manitoba. His father, Joe Highway, was a caribou hunter. His 2001 children's book entitled "Caribou Song/atíhko níkamon" was selected as one of the "Top 10 Children's Books" by the Canadian newspaper "The Globe and Mail." The young protagonists of "Caribou Song", like Tomson himself, followed the caribou herd with their families. Heraldry and symbols. Several Norwegian municipalities have one or more reindeer depicted in their coats-of-arms: Eidfjord, Porsanger, Rendalen, Tromsø, Vadsø and Vågå. The historic province of Västerbotten in Sweden has a reindeer in its coat of arms. The present Västerbotten County  has very different borders and uses the reindeer combined with other symbols in its coat-of-arms. The city of Piteå also has a reindeer. The logo for Umeå University features three reindeer. The Canadian 25-cent coin or "quarter" features a depiction of a caribou on one face. The caribou is the official provincial animal of Newfoundland and Labrador, Canada, and appears on the coat of arms of Nunavut. A caribou statue was erected at the centre of the Beaumont-Hamel Newfoundland Memorial, marking the spot in France where hundreds of soldiers from Newfoundland were killed and wounded in  World War I. There is a replica in Bowring Park in St. John's, Newfoundland's capital city. Two municipalities in Finland have reindeer motifs in their coats-of-arms: Kuusamo has a running reindeer and Inari has a fish with reindeer antlers.