Migratory Woodland Caribou - Woodland Caribou in Ontario

Woodland Caribou in Ontario

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 northern Wisconsin. The last permanent residents were killed in Minnesota in 1962. Despite periodic sightings of individuals south of the border the 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. There is a large herd isolated on the Slate Islands in Lake Superior.

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 lag 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.

Logging also is a major cause of caribou mortality. Logging the mature boreal forest of northern Minnesota, Wisconsin, Michigan, and Ontario has led to creeping aspen/birch habitat followed by northward moving whitetail deer carrying the parasite Parelaphostrongylus tenuis. The neurological parasite is fatal to caribou and moose.

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 may have 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.