Fall Migration - Caribou Activities

August to October

During August, insect pests become less abundant than earlier in the summer, and eventually disappear. Caribou still travel widely in search of the best feeding areas, but they no longer need to congregate in insect relief areas. Thus the large aggregations break up and caribou disperse widely. Mortality rates often increase as caribou come in contact with more predators. Sometime in late August or early September the caribou stop moving erratically and their travels become more directional. Often a storm or cold weather starts them moving south toward winter range. Fall migration has begun. Once again, larger groups form as caribou start moving in the same direction.

The rut, or mating season, in early October usually occurs when fall migration is still underway. Caribou are in the fattest and best condition of the year after the summer feeding and growing season. Bulls use their huge antlers to fight each other, and the largest, dominant males do most of the breeding. Fighting during rut puts a great strain on the dominant bulls and puts them in weakened condition before the harsh winter season. Smaller bulls usually come through rut in better shape, meaning they will stand a better chance of surviving winter and breeding in future years.

Fall migrations are often spread over a large area, with caribou moving in the same direction but along many parallel paths. By late October or early November, caribou from the Porcupine Herd have usually moved deep into the taiga or boreal forest, though in some years many will remain north of the treeline all winter.

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