Single calves are born in May or June. Gestation is about 228-234 days and the rutting season is in October. Maximum longevity is about 13 years for males and 17 years for females. Age of first breeding (1 to 3 years of age) depends on body size hence summer nutrition is important.
CaribouThe caribou, a member of the cervidae (DEER family), is a symbol of Canada's North and is represented on the 25-cent piece. This ungulate evolved in North America and spread to Euroasia where they are known as reindeer. The earliest fossils of caribou in North America are 1.3-1.8 million years of age and are from the Beringia refugium, in Alaska and northwestern Yukon. These animals became the barren-ground caribou (Rangifer tarandus groenlandicus) spreading east to Hudson Bay and south to the boreal forest. Woodland caribou (R.t. caribou) survived the Pleistocene in the Appalachian Mountains. They moved north in the Holocene and reached Lake Ontario and the boreal forest 10 000 years ago. They also colonized the Québec-Labrador Peninsula. Peary caribou (R.t. pearyi) possibly survived the Pleistocene on Banks Island and spread to the Queen Elizabeth Islands after the last ICE AGE.
DescriptionWeights vary between subspecies, males varying from 125-275 kg and females 90 kg-139 kg. Newly born calves weigh 5-9 kg. Adult males have tall antlers with some vertical palmation (flat handlike lobes). Females have smaller antlers. Pelage (body covering) can vary from nearly white in some tundra populations to dark brown in woodland herds. Caribou hooves are broad and their pelage is dense with hollow hairs - adaptations for warmth and swimming. It is the strongest swimmer of the deer family as well as the best runner; both adaptations improve escape.
Single calves are born in May or June. Gestation is about 228-234 days and the rutting season is in October. Maximum longevity is about 13 years for males and 17 years for females. Age of first breeding (1 to 3 years of age) depends on body size hence summer nutrition is important. Caribou have several mates. Males seek nutritious forage to maximize body size for competition with other males. The reproductive fitness of females is enhanced by choosing safe habitats to raise her single calf. This dichotomy has resulted in females being more wary than males.
Caribou have broad food habits. Plant groups utilized include LICHEN in the winter and deciduous shrubs in the summer. Other groups utilized are mushrooms, grass and sedges, forbs, aquatics, ferns, mosses, horsetails and conifers.
In winter when caribou dig for lichens, they select open habitat sites with reduced snow cover rather the areas with maximum lichen biomass. Increased visibility decreases the chance of ambush and minimal snow cover maximizes escape speed. When foraging caribou are threatened, their escape route is to the nearest wind swept frozen lake where snow cover is reduced. Barren-ground caribou use the increased safety of frozen lakes for resting, ruminating and migrating.
MigrationBarren-ground caribou are probably the most wide-ranging land mammal in North America. In the spring some barren-ground females migrate en masse hundreds of kilometres to Arctic calving grounds that have reduced forage, late phenology (when green plants begin to appear in spring) and often some snow cover. This migration results in spacing away from the treeline where WOLVES commonly den, thus improving calf survival. Woodland females migrate generally less than 50 km, and disperse away from other females and alternate prey such as MOOSE. They seek high mountain slopes, islands or shorelines where they can reduce the probability of being found by predators or increase escape by swimming.
Many woodland caribou populations are now extinct including 4 herds in NATIONAL PARKS where logging is prohibited and anthropogenic disturbances are minimum. All the woodland caribou south of 60º N have been classified as threaten by the COMMITTEE ON THE STATUS OF ENDANGERED WILDLIFE IN CANADA (COSEWIC) in 2002. Two herds are listed as endangered - the southern most caribou in British Columbia and a small herd on the Gaspé Peninsula. Recent global warming has resulted in moose and deer increasing and moving north. Since the abundance of predators depends on the biomass of their prey, wolves, COUGARS and COYOTES are all expanding their ranges and increasing. Southern woodland caribou, unlike moose and deer, cannot coexist with such high predator numbers and will go extinct unless humans intrude. Peary caribou are also listed as endangered. Warming temperatures in the High Arctic (seeCLIMATE CHANGE) have resulted in an increase of ice and hard snow crusts on vegetation leading to reduced pregnancies and increased starvation.
Aboriginal peoples harvest thousands of caribou, waiting each year for the long line of migrating caribou that trek in single file down trails followed for millennia. Some First Nations groups have been instrumental in protecting the habitat of certain caribou populations, for example in TUKTUT NOGAIT (NWT) and VUNTUT (Yukon) national parks.
A.T. Bergerud, "Caribou," Chapter 13, Ecology and Management of Large Mammals in North America (2000), A.T. Bergerud, N. Luttich, and L. Camps, The Return of Caribou to Ungava (2008); George Calef, Caribou of the Barren Lands (1981).