These members of the antelope family number 13,000–15,000 in Alaska [1]. They have snow-white coats, shaggy heads, and black spiked horns up to a foot long, and they weigh in at 150–300 pounds. They mostly inhabit the coastal ranges and eastern Alaska Range and are frequently seen high on cliffs so precipitous that they would probably scare even Dall sheep.
Links:
[1] http://www.moon.com/destinations/alaska