page_title: Reindeer
section_title: Predators
hierarchical_section_title: Reindeer / Ecology / Predators
caption_attribution_description: English: Numerous reindeer standing on patches of snow during summer to avoid blood-sucking mosquitoes and gadflies.
context_page_description: The reindeer, also known as the caribou in North America, is a species of deer with circumpolar distribution, native to Arctic, sub-Arctic, tundra, boreal, and mountainous regions of northern Europe, Siberia, and North America. This includes both sedentary and migratory populations. Rangifer herd size varies greatly in different geographic regions. The Taimyr herd of migrating Siberian tundra reindeer 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 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 caribou in the contiguous United States with an expert calling it "functionally extinct" after the herd's size dwindled to a mere three animals.
  Rangifer varies in size and colour from the smallest, the Svalbard reindeer, to the largest, the boreal woodland caribou.
context_section_description: 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 the 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.
  Additionally, as carrion, reindeer may be scavenged opportunistically by foxes, hawks and ravens.
  Bloodsucking insects, such as mosquitoes (Culicidae), black flies (Simuliidae), and botflies and deer botflies (Oestridae, specifically, the reindeer warble fly (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 1 liter (about 2 US pints) 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.
  In one case, the entire body of a reindeer was found in the stomach of a Greenland shark, a species found in the far northern Atlantic, although this was possibly a case of scavenging, considering the dissimilarity of habitats between the ungulate and the large, slow-moving fish.
caption: Reindeer standing on snow to avoid bloodsucking insects.
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