<P> There are four living subspecies of R. tarandus, locally known in North America as caribou--Rangifer tarandus caribou subdivided into ecotypes: woodland (boreal), woodland (migratory), woodland (montane), R. t . granti, R. t . groenlandicus and R. t . pearyi . </P> <P> In North America, because of its vast range in a wide diversity of ecosystems, the subspecies Rangifer tarandus caribou is further distinguished by a number of ecotypes, including boreal woodland caribou, mountain woodland caribou and migratory woodland caribou). Populations--caribou that do not migrate--or herds--those that do migrate--may not fit into narrow ecotypes . For example, Banfield's 1961 classification of the migratory George River Caribou Herd, in the Ungava region of Quebec and Labrador, as subspecies Rangifer tarandus caribou, woodland caribou, remains--although other woodland caribou are mainly sedentary . </P> <P> Although there are remnant populations of R. t . caribou boreal woodland caribou in the northern United States, most of U.S. caribou populations are in Alaska . There are four herds in Alaska, the Western Arctic herd, Teshekpuk Lake herd, the Central Arctic herd and the Porcupine herd . </P> <P> Alaska has several herds of R. t . granti . The largest is the Western Arctic Caribou Herd but the smaller Porcupine caribou herd has the longest migration of any terrestrial mammal on earth with a vast historical range . The smaller Central Arctic herd (32 000 in 2002). </P>

Where do caribou live in the united states