Caribou have special adaptations that allow them to survive their harsh arctic environment. Long legs and broad, flat hooves allow them walk on snow, and a dense woolly undercoat overlain by stiff, hollow guard hairs helps keep them warm. Caribou are also the only member of the deer family in which both sexes grow antlers. Antlers of adult bulls are large and massive; those of adult cows are much shorter and are usually more slender. In late fall, caribou are clove-brown with a white neck, rump, and feet and often have a white flank stripe. Weights of adult bulls average 350 to 400 pounds and females average 175 to 225 pounds.Barren Ground Caribou (Rangifer tarandus granti)In the United States, Alaska is the only state that supports a healthy barren ground caribou population. Barren ground caribou are found in the arctic tundra, mountain tundra, and northern forests of North America, Russia, and Scandinavia.Calving occurs in late May to early June. After calving, barren ground caribou collect in large “postcalving aggregations”. Migration then begins in the fall, where large herds often travel long distances (up to 400 miles) between summer and winter ranges. During the summer, barren ground caribou feed on the leaves of willows, sedges, flowering tundra plants, and mushrooms. They switch to lichens, dried sedges, and small shrubs during the fall.Portions of four different barren caribou herds winter on or near Tetlin Refuge. The Nelchina Herd (> 30,000 animals), makes up the majority of caribou that pass through or winter on the Refuge. The Fortymile Herd (> 40,000 animals) is generally found north of the Refuge during the winter, although occasional individuals are also on Refuge lands. The remaining two herds are much smaller (< 1,000 animals). The Mentasta Herd calves on the slopes of Mt. Sanford in the Wrangell Mountains with a few individuals lingering some years in the southwest portion of the Refuge. The Macomb Herd calves northwest of the Refuge on the Macomb Plateau, and rarely moves onto Refuge lands.Woodland (Mountain) Caribou (Rangifer tarandus caribou)Canada’s boreal forests host nearly the entire global population of woodland caribou. Woodland caribou are also found along the southeastern edge of Alaska and northeastern Washington State, and are listed as vulnerable to endangered across much of their range. This subspecies tends to remain in forested habitats year-round, occur in small groups, and are not generally associated with the long distance migrations defined by large herds of the barren ground subspecies.Woodland caribou generally prefer mature or old growth coniferous forests. These forests offer high concentrations of ground and tree lichens, which make up a significant proportion of their winter diet. During the winter, woodland caribou tend to use uplands, bogs and south facing slopes. In summer, they prefer areas such as forest edges, marshes and meadows that provide flowering plants and grasses.The Chisana Herd is the only woodland caribou herd in Alaska. Potential population concerns have recently sparked cooperative efforts led by the Yukon Territory government to attempt new management techniques. The Chisana Herd spends most of its time in the headwaters of the Chisana River, Beaver Creek, and White River in both the Yukon Territory and Alaska, although occasionally some animals do move north onto Tetlin Refuge.
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Thousands of birds like this Wilson's Warbler are banded each fall at the Refuge's migration banding station near Tok.