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Woodland caribou ecology

© Van Waffle

Earlier this month a series of news articles appeared, concentrating on the decline of the woodland caribou, Rangifer tarandus caribou. A conservation organization, the Canadian Parks and Wilderness Society, has launched a campaign to save this member of the deer family. Its range is threatened by industrial pressure on boreal forest habitats. The disappearance of woodland caribou holds serious implications for these environments.

The woodland caribou is just one of four subspecies found in Canada and Alaska. The Peary caribou, R. t. pearyi, occupies Canada's arctic islands, ranging as far south as the mainland coast. The barren-ground caribou of Alaska, R. t. granti, and the Northwest Territories and Nunavut, R. t. groenlandica, are known for their migratory behaviour, travelling between tundra in the summer and boreal forest in the winter. Other subspecies are less migratory.

The woodland caribou, R. t. tarandus, is the most southerly subspecies, and has the widest range: from southern Alaska, northern British Columbia and the Yukon, through the Northwest Territories, northern Saskatchewan, Manitoba and Ontario, Quebec, Labrador and Newfoundland. A small remnant population occupies southern British Columbia and Idaho, possibly also Montana and Washington state. Although the population totals 184,000, more than 100,000 live in Newfoundland and Labrador.

Caribou are considered a primitive species of the deer family because of several physiological traits. The most obvious is that both males and females bear antlers. Caribou have wide hooves specially adapted for walking on tundra and muskeg. Their circulatory systems are adapted for preserving heat in winter, and fat deposits prevent their feet from becoming stiff in extreme cold.

Woodland caribou is dependant on large tracts of undisturbed boreal forest. The herds stay deep in the forest, avoiding edge habitats where they may be more susceptible to predators. Boreal forests are declining due to logging, and are being carved into smaller portions because of hydroelectric cuts and oil pipelines. Caribou habitat in northern Alberta and Ontario has shrunk by 40 per cent.

Caribou habitat in the southern portion of its range has been lost due to the elimination of climax forests. The northward extension of white-tailed deer populations have also contributed, through competition for food. The parasitic meningeal worm, Parelaphostrongylus tenuis, which is carried by deer, has probably contributed.

Caribou are specially adapted for consuming and metabolizing lichens. One of their staples is reindeer lichen, Cladonia rangiferina, found in wide abundance in the arctic. In winter, caribou may survive solely on lichen, but will graze on trees depending on availability. Lichen are high in carbohydrates and low in protein. Specially adapted bacteria in the caribou's rumen produce

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