Both ewes and rams have horns, but the male's horns are much larger. Instead of shedding their horns every winter like deer and elk shed their antlers, bighorns keep them year-round. They're called sheep, but bighorns are quite different from the farm animals. Bighorns have hollow hair that traps body heat. This helps protect them from the cold.
Bighorns also are bigger than tame sheep.
A bighorn ram can weight as much as 300 pounds, about the same as two human adults. Once, wildlife biologist Valerius Geist was studying bighorns by sitting in the middle of a herd. Soon, one ram began to threaten him with little kicks. Geist knew he'd better do something before the ram charged. So, the next time the sheep pestered him, Geist did what any bigger ram might do.