A third subspecies, reindeer originally descended from Siberian stock, was introduced to the Belcher Islands in eastern Hudson Bay in 1978, about 100 years after native caribou had disappeared. Concerned that unrestricted growth of this free-ranging population could lead to overgrazing and potential future extinction, Inuit of Sanikiluaq have successfully stabilized their numbers at 600 to 800 animals. There are concerns that some woodland caribou from Quebec have migrated across 100 kilometres of sea ice, and some of the reindeer have joined them on their return to Quebec. Caribou bulls average 100 to 150 kilograms, while cows reach 75 to 100 kilograms. The types of caribou differ in size, color and behavior.
Peary caribou are the smallest.
During summer, Peary and Baffin caribou are not known to form dense groups numbering in the thousands, as do the barren-ground caribou on the mainland, perhaps because they do not have to endure thick clouds of mosquitoes and other insects. Reindeer are typically seen in large, dense groups, even during winter. Unlike caribou, which prefer slow-growing lichens, muskoxen depend largely on grasses and sedges that recover relatively quickly from heavy grazing. In the summer, these herbivores may be seen in river valleys, along lake shores and near damp meadows. If grasses and sedges become unavailable in winter, muskoxen move onto ridges and hilltops to feed on willows and other plants.