Post-calving Groups - Caribou Activities


Late-June to July

The post-calving period occurs in the middle of the summer, after the new calves are born. This is the time when the plants that caribou eat are the most abundant and at their highest quality. By eating a lot of these plants, caribou grow during this time, and they also store the fat they'll need to survive through the long winter ahead. Bulls put on fat and grow large antlers. Cows grow much smaller antlers and regain some of the weight they have lost during the winter and calving periods, but most of the nutrients they get from the plants they eat goes into milk for their calves. When the calves are three weeks to a month old, they begin to wander with their mothers in search of the best feeding areas.

The post-calving period is also the time of year when hordes of insects emerge and torment the caribou. To escape these pests, caribou travel to beaches and river deltas or run up onto mountains and ridgetops, where cool winds and lack of vegetation keep insect numbers lower than in calm valleys or out on moist tundra. Caribou drift about erratically between favored feeding areas on cool days or at night, and places where they can escape from insects on warm, still days. In addition, cows without calves, yearlings, and many adult bulls continue moving toward the calving area and eventually catch up with the mothers and calves. Caribou actually move about more now than at any other time of year, including during their migrations, but now their movements are haphazard and irregular.

As all these caribou move back and forth between feeding and insect-relief areas, they tend to encounter each other, gather together and mill about in larger and larger groups. These large groups offer extra protection from insects, at least for those caribou in the middle. After a few days of warm temperatures and little wind, nearly all the female and calf caribou in the Porcupine Herd, and often most of the bulls, can be found in a few very large groups, called aggregations, on insect-relief areas near the coast or on high hills near the mountains. The remainder of the adult bulls will also be in a few large groups on mountain tops, though they may be a hundred miles or more away from the bigger groups containing the cows and calves.

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