The Selection of Snowpatches as Relief Habitat by Woodland Caribou (Rangifer tarandus caribou), Macmillan Pass, Selwyn/Mackenzie Mountains, N.W.T., Canada

Abstract

Woodland caribou (Rangifer tarandus caribou Gmelin) occupy the Mackenzie and Selwyn Mountains of the Yukon and N.W.T, Canada. During the warm weather months they move into alpine areas and are frequently observed to utilize late-lying snowpatches. Microclimatic observations confirm that at 0.5 m height the snowpatch is consistently 3?C cooler than adjacent areas. Insect trap data indicated that significant differences in numbers and species occur between snowpatches and adjacent snow-free areas at the same and lower elevations. Indices of harassment correlated with biting insect numbers and with higher air temperatures (11.3 to 20.4?C, shielded temperatures) and below-average wind speeds (<2.5 m s-1). Group size on snowpatches was significantly greater than on adjacent snow-free areas. While on snowpatches animals ingested snow and otherwise spent most of their time standing or lying. These activities we interpreted as behavioral thermoregulation. However, based on our data it was not possible to separate definitively microclimatic conditions from insect harassment as cause for snowpatch selection as relief habitat.