Distributed across Alaska in 32 different herds, caribou (Rangifer tarandus) are the only member of the deer family (Cervidae) in which both sexes grow antlers. Antlers of adult bulls are large and massive, while those of adult cows are much shorter and are usually more slender and irregular. Adult bulls also average between 350 and 400 pounds, with weights of up to 700 pounds recorded. Mature females, on the other hand, average between 175 and 225 pounds. Additionally, caribou in northern and southwestern Alaska are generally smaller than caribou in the Interior and in southern parts of the state.
The species generally prefers treeless tundra and mountain habitats, though many of the herds will also winter in the boreal forest (taiga). And like most herd animals, the caribou must keep moving to find adequate food. Large herds often migrate long distances (up to 400 miles) between summer and winter ranges, with movements most likely triggered by changing weather conditions, such as the onset of cold weather or snowstorms. Once they decide to migrate, caribou can travel up to 50 miles a day, utilizing what amounts to an apparent built-in compass, like migratory birds, to sometimes travel through unfamiliar areas to reach their calving grounds. These calving grounds tend to be in the same general area year after year, with each herd using an area separate from other herds to calve, though the herds will occasionally mix together on winter ranges.
After calving (mid- to late May in interior Alaska and in early June in northern and southwest Alaska), caribou collect in large post-calving aggregations to avoid predators and escape mosquitoes and warble flies. These large groups of caribou stay together in the high mountains and along seacoasts where wind and cool temperatures protect them from summer heat and insects. The shedding of velvet in late August and early September by large bulls marks the approach of the rut and the start of fall migration.
Caribou are somewhat cyclic in number, but the timing of declines and increases, and the size to which herds grow, is not very predictable. Still, caribou hunting remains extremely popular in Alaska, for both resident and non-resident hunters alike, though for most it remains a feast or famine type of hunt, depending upon the species’ extraordinarily migratory behavior. Hunters that do their homework, double-checking with local area biologists and air taxi operators, inevitably do better over the long run.