The reindeer (Rangifer tarandus), 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 (R. t. sibiricus) in Russiais the largest wild reindeer herd in the world, with numbers 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.