Calves, Corridors, and Caribou: Massive Mammalian Migration in Canada’s NWT

The Bathurst caribou herd of Canada’s Northwest Territories has been intensely studied for the past three decades as the result of a dramatic population decline. Caribou undertake impressive annual migrations, leaving lower-latitude winter browsing ranges for northern summer ranges and calving grounds. While generalized documents and maps defining the herds range have been made available to the general public, these documents do not address interannual herd migration trends or delineate areas of greatest use and conservation concern. In this project, I performed point-density analysis and generated time lapse animations using migration data from satellite transmitters on tagged caribou (satellite telemetry) to identify high-use regions and effectively communicate overland movement patterns. While caribou often follow meandering, nonlinear migratory routes between summer and winter ranges, most migration activity fell within a 3,000 km² swath of land. Summer ranges and calving grounds were not identical across years, but they tended to fall within similar regions – a trend which emerged both in the density analysis and time series animations. Winter ranges were far more variable, generally occupying territory at similar latitudes from year to year, but with a broad East-West distribution. My results identify these overall migration trends and suggest that future caribou conservation efforts may be well-served by establishing permanent protected areas around the most-commonly used calving grounds and summer ranges, as pregnant females and young calves are vulnerable to predation and environmental stressors at these sites and times of the year