Named for William H. Dall, one of the first people to survey the lower Yukon (1866), Dall sheep are sometimes called Alaska bighorn sheep, because the Rocky Mountain bighorn is a closely related species. Distinguished by their brilliant white color, the rams grow large curved horns, formed from a specialized skin structure made up of a compacted mass of hair and oil.
The horns aren’t shed; instead the sheep add another ring to them yearly, so the longer the horns, the older the ram, and the more dominant within the herd. The rams can weigh as much as 175 pounds; the ewes have small spiked horns and average 120 pounds.
Their habitat is the high alpine tundra, and they subsist on grasses, mosses, lichens, and flowers. Their bird’s-eye view provides an excellent defense. They’re also magnificent mountain climbers. Roughly 70,000 Dall sheep reside in the Chugach, Kenai, Alaska, and Wrangell mountain ranges.
During summer, the rams migrate high into the ranges, leaving the prime lower grazing grounds for the ewes and lambs. It’s natural that they migrate, the same way it’s natural that they have predators. Their alpine tundra habitat is very fragile, and it can take decades to regenerate after overgrazing. Migration and predation thus keep the flock healthy, control population growth, and guarantee the survival of the habitat.
Dall sheep inhabit mountain hillsides throughout much of Alaska. They are frequently seen on rocky slopes in Denali National Park , near Atigun Pass on the Dalton Highway, near Cooper Landing  on the Kenai Peninsula , and along Turnagain Arm  20 miles south of Anchorage .