Why are some Porcupine Caribou herd calves born in Canada or the mountains?
In spring the Porcupine caribou herd migrates hundreds of miles from winter ranges located south of the Brooks Range in Alaska, and from areas in Yukon Territory, to its traditional calving grounds on the Arctic Refuge’s coastal plain and foothills. In years when there’s deep snow on the winter range and along the migration routes, and when the spring snow melt is delayed by cold temperatures, caribou cows are delayed in reaching these preferred calving grounds. When this happens, the calves are born along the migration routes and on calving habitats in Canada. This happened in 1987, 2000 and 2001. Sometimes caribou are not delayed during the spring migration, but when they arrive at the edge of the foothills they find it is still covered by snow because cold temperatures have delayed snow-melt. In this case, the cow caribou give birth in snow free or partially snow free areas to the south, near or in the northern mountain valleys. This happened in 1988. In 1987, 1988, 2000 and 2001, n
