Snow as a Factor in the Winter Ecology of the Barren Ground Caribou (Rangifer arcticus)

Discusses the effects of snow cover on the behavior, migration and species survival of caribou, from field studies in southern Mackenzie and Keewatin Districts during the winter 1957-58. Snow observation records were taken at 114 stations, caribou distribution was plotted during low altitude flights, and ground observations made of their behavior in relation to snow conditions. Correlations were found between areas of heavy caribou concentration and the snow hardness, density and thickness. Caribou appear to have sensitivity thresholds: approx. 50 gm/sq cm hardness for forest snow and 500 gm/sq cm for lake snow; approx. 0.19-0.20 density for forest snow and 0.25-0.30 for lake snow; and approx. 60 cm thinkness. When these thresholds are exceeded, the animals move to areas of softer, lighter and thinner snow. Location of the winter range and the timing, direction, speed and routes of annual migrations are intimately related to snow cover characteristics. Protection of vegetation in areas of favorable snow conditions may be of prime importance to the survival of caribou. Further research is needed.