Caribou Info Page

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Description
The caribou Rangifer tarandus is a medium-sized member of the deer family, Cervidae, which includes four other species of deer native to Canada: moose, elk, white-tailed deer, and mule deer. All are ungulates, or cloven-hoofed cud-chewing animals. However, only in caribou do both males and females carry antlers. Caribou are similar to and belong to the same species as the wild and domesticated reindeer of Eurasia.
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The caribou is well adapted to its environment. Its short, stocky body conserves heat, its long legs help it move through snow, and its long dense winter coat provides effective insulation, even during periods of low temperature and high wind. The muzzle and tail are short and well haired.

Signs and sounds
Caribou are usually quiet, but they may give a loud snort. Herds of snorting caribou may sound like pigs. Especially vocal are the bands of cows and new-born calves, constantly communicating with each other.

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Habitats & Habits

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There are more than 2.4 million caribou in Canada. Some dwell in forests, some in mountains, some migrate each year between the sparse forests and tundra of the far north, and others remain on the tundra all year.

The woodland caribou is the largest and darkest of the caribou subspecies. It is found throughout much of the boreal, or northern, forests from British Columbia and the Yukon Territory to Newfoundland and Labrador. In mountainous areas of western Canada, woodland caribou make seasonal movements from winter range on forested mountainsides to summer range on high, alpine tundra. Farther east, in the more level areas of boreal forest, many woodland caribou occupy mature forest and open bogs and fens, or low-lying wet areas. Some may move only a few kilometres seasonally, while others may wander extensively. A few herds differ from this pattern, making long seasonal movements between forested and tundra habitats. The Leaf River and George River herds in Quebec and Labrador are the largest of these herds. They are also among the biggest caribou herds in North America, at about 600 000 and 400 000 individuals respectively.

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Range
In Canada, caribou are found from the United States–Canada boundary to northern Ellesmere Island, more than 4 000 km north, and from British Columbia and the Yukon Territory in the west to the island of Newfoundland in the east. The southern limit of caribou distribution has receded northward since European settlement and this recession continues today.
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Feeding
Ground and tree lichens are the primary winter food of caribou, providing a highly digestible and energy-rich food source. The ability of caribou to use lichens as a primary winter food distinguishes them from all other large mammals and has enabled them to survive on harsh northern rangeland. Caribou use their excellent sense of smell to locate lichens under the snow, and they dig the lichens out with their wide hooves. In southern coniferous forests they are also able to forage on tree lichens.
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Although lichens are a good source of energy, they are not a good source of protein (nitrogen). As soon as spring snow melts, caribou are eager to switch to fresh green vegetation, which is rich in nitrogen. Cows that have just given birth are especially in need of protein to replenish their protein reserves and produce high quality milk for their calves. At this time of year caribou focus on sedges and newly unfurling leaves of willow and other shrubs. Flowers, plentiful on the tundra, also attract a lot of attention. As summer progresses and the quality of the green vegetation declines, caribou once again turn to lichens, to fatten themselves up for the breeding season. Although not always available, mushrooms are highly sought after in August and September. Mushrooms provide a rich nitrogen source late in the summer.

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Breeding
Although all caribou move about for different functions over the course of a year, barren-ground caribou make the most dramatic treks. They are the most efficient walkers of all ungulates in North America, and they are good navigators, unerringly walking hundreds of kilometres from the taiga to their relatively small calving areas on the tundra in spring. They tend to follow frozen lakes and rivers, open snow-free uplands, and eskers, or long narrow hills of soil and rock dumped by glaciers. Caribou are able to keep a steady direction across frozen lakes so large that the opposite shore cannot be seen.
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Pregnant barren-ground caribou cows lead the spring migration, followed by juveniles, bulls, and non-pregnant cows, which tend to lag farther and farther behind. Barren-ground caribou cows head toward traditional calving grounds, where they gather to calve year after year, even from different wintering areas.

In contrast, to avoid predation smaller woodland herds generally calve in isolation either in rugged terrain or on islands in small lakes.

Caribou cows are usually at least three years old before they can bear young, though 10 to 25 percent of two-year-old cows can also give birth. Cows produce one calf a year, and about 90 percent of adult cows give birth annually. Most of the calves are born during a 10-day period in May or early June. Calving time tends to be later the further east in North America the caribou are found.

The calves are well developed at birth and are able to travel within a few hours. They start to graze during their first weeks, but until they are about three weeks old, they can digest only milk. The cows and calves soon move to areas where fresh-growing feed is becoming abundant.

During summer barren-ground caribou are often harassed by hordes of mosquitoes, warble flies, caribou nostril flies and, in some areas, black flies. Sometimes the agitated animals will run for many kilometres, stopping to rest only when exhausted or when high winds temporarily disperse the insects. Running from insects places great energy demands on the caribou and may slow their rate of growth by temporarily reducing their search for food. In large herds, another strategy to reduce harassment of individual animals is to form large gatherings of caribou. These tight groups can number in the tens of thousands.

By late September the herds, fat and in good condition, arrive in pre-rutting (pre-mating) areas. The rut occurs from mid-September to early November depending on the region. Bulls spar a great deal and sometimes fight for possession of cows. Normally, during the rut, cows will wean their calves, encouraging them to eat food other than their mothers’ milk. If the calf is too small, the cow will continue to supply milk into the winter, but this reduces her chances of getting pregnant that autumn.

In the deer family, antler size means dominance. By late winter when conditions are most severe, pregnant females are the dominant members of the herd, because they are the only ones to have retained their antlers. The large bulls lose their antlers after the autumn mating season, and the non-breeders lose theirs soon after that. The females’ dominance allows them to defend their feeding craters from larger caribou and even displace larger caribou from favoured sites. This is important when conditions are harsh, as the pregnant cows need energy to develop the fetus. Most pregnant females will keep their antlers until after they give birth in June.