The migratory woodland caribou (in Latin, Rangifer tarandus caribou) of Northern Quebec and Labrador live in two wild herds, the Leaf herd with 628,000 individuals and the George River herd with 385,000 individuals. The caribou generally travel upwards of 2,000 km annually and live in an area of about 1,000,000 square kilometres. Some individuals have been observed traveling 6,000 km in a single year.
The caribou population varies considerably, for unknown reasons, and their numbers have apparently peaked in the later decades of each of the 18th, 19th and 20th centuries. The most recent decline at the turn of the 20th century caused much hardship for the Inuit and Cree communities of Nunavik, Quebec, who hunt them for subsistence. By 1950, as few as 5,000 caribou remained in Northern Quebec and Labrador.
The George River herd, south of Ungava Bay, whose numbers reached about 800,000 towards 1993, had about 384,000 individuals in 2001. The Leaf herd in the west, near the coast of Hudson Bay, has grown from 270,000 individuals in 1991 to 628,000 in 2001. Inuit, Cree and southern sport hunters kill about 30,000 caribou each year in Northern Québec.
A much smaller population of migratory woodland caribou, perhaps numbering about 20,000, is found in Northern Ontario, on the coastal plains south of Hudson Bay.
Woodland caribou were once found throughout much of Ontario's boreal forest; at the turn of the 20th century they ranged as far south as the Canada-United States border. However, caribou range has receded approximately 34 km/decade, the manifestation of widespread range collapse and population decline. Although woodland caribou have been protected from sport hunting since 1929, the Committee on the Status of Endangered Wildlife in Canada listed forest-dwelling caribou in Canada as threatened (likely to become endangered if limiting factors are not reversed) in 2000. Woodland caribou may be extinct before the year 2100 if the rate of range loss continues.
Human-caused landscape disruption is the chief cause of caribou range recession. For example, the conversion of forests by logging may result in greater abundance of other ungulates, like moose, and increased predation by wolves. Linear corridors, such as roads, utility corridors, and trails may improve travel speed and hunting efficiency for predators, improve access for poachers, and hinder caribou movements.
Cutovers from forest harvesting have been identified as the strongest predictor of caribou extirpation. This was not surprising; the northern front of forest harvesting in Ontario closely matches the southern boundary of continuous caribou occupancy and timber harvesting may lead to reduced occurrence of woodland caribou. However, there appears to be a time lag between forest harvest and disappearance of caribou. Research suggests that there is a two decade time lage between disturbance by forest harvest and disappearance of caribou. Forest harvest converts forest stands to early seral stages, which are favoured by moose, which in turn can support a higher wolf population than caribou alone. A higher wolf population may increase predation mortality of caribou. Thus, two decades is likely the time necessary for these faunal changes to take place. This time lag is cause for concern, as there is overlap of forest harvest with the southern boundary of caribou range in Ontario. Caribou in these areas are very likely to vanish in the next 20 years. While patterns of forest harvest show the strongest relationship with caribou extirpation in Ontario, strong correlations among landscape disturbances suggest that no single variable can be unequivocally implicated as key to caribou range recession.
Woodland caribou persistence in Ontario will likely depend on the availability of large tracts of old growth forest situated at great distances from anthropogenic disturbance. Recent research suggests that forest harvest operations should be buffered from caribou habitat by at least 13 km.
Climate change has negative potential for woodland caribou as well. Climate change may further alter forest structure to favour moose and white-tailed deer, which may carry the parasite Parelaphostrongylus tenuis; lethal to caribou but not harmful to deer. In addition, increased episodes of freezing rain in the winter may make it difficult for caribou to dig through the snow to reach their primary food source, lichens. The effects of climate change on woodland caribou have not been studied.
In September 1984, about 151 km south of the Northern village of Kuujjuaq, Québec, about 10,000 caribou (about 1.5% of the George River herd) drowned while crossing the Calcaire Falls on the Caniapiscau River, a tributary of the Koksoak River that flows into southern Ungava Bay. Although the caribou regularly criss-cross northern rivers and lakes and can swim 10 km at a stretch, northern rivers and lakes often claim lives during their annual migrations. At the time of the accident, observers raised questions about the management of the newly built reservoir on the headwaters of the Caniapiscau River, some 450 km upstream, and focused their attention on decisions made in the days following the exceptionally heavy rains in September 1984. The Caniapiscau Reservoir is part of the La Grande hydroelectric complex in Northern Quebec. The waters of the upper Caniapiscau River, which flow north, were diverted to the La Grande River of the James Bay watershed to the west.
After investigation, the Québec Recreation, Hunting and Fishing Department – whose employee had discovered the dead caribou on September 30th -- came to the conclusion that a larger number of caribou would have perished had the Caniapiscau Reservoir not yet been built, since the water flow at the falls would have been even greater in the absence of the reservoir.
On the other hand, in a short but savvy analysis, Quebec’s Indian and Inuit Secretariat (SIGMAI) expressed the opinion that the fast-growing George River herd may have become accustomed to the reduced water flow from 1981 to 1984, during which time the reservoir was being filled. SIGMAI hypothesizes that the caribou may have been surprised as the water flow of the Caniapiscau River was partially restored to its natural state in mid-September 1984, after the filling of reservoir had been completed. The partial release of the headwaters back into the Caniapiscau was necessary because the power stations on the La Grande River could not yet turbine the full water flow. According to Hydro-Québec, any major addition of water to the La Grande River would by necessity have been diverted around the power stations for months, even years, and seriously damage the floodgates which were designed for temporary use during exceptional climatic events.
Thus, SIGMAI chastised the Société d'énergie de la Baie James, a subsidiary of Hydro-Québec, that had just completed the construction of the reservoir, for not having planned to actively manage the restored water flow to the Caniapiscau River in such a way as to protect the caribou herd from exceptional floods caused by heavy rains or rapid spring thaw. This was a rather novel idea at the time, as no Canadian wildlife expert had foreseen anything more than the usual mortality along the rivers of the region (up to 500 deaths every year).
The Quebec game officials did, however, put forward the opinion that a dynamic management of the water levels and flows of the Caniapiscau Reservoir could have avoided the high mortality observed in September 1984, either completely, or at least reduced it to levels observed in recent years. SIGMAI finally recommended that the water levels of the reservoir be lowered by about 0.5 meter for several months of the year in order to avoid the use of the flood gates during extreme rainfalls when the caribou are migrating in late summer and early fall. Of course, this is largely a moot point today, since virtually no water has been diverted back into the lower Caniapiscau since 1985. Furthermore, a fence was installed to divert the herd from the danger zone near the Calcaire Falls.