The maximum circumference at the base of the Dall horn is 400 mm. The two horns of a male, with their cones, may weigh over 13 kg. These horns grow from the skin over a conical bony core and are never shed. They grow throughout life, producing a prominent check line, or annulus, each winter when growth slows. This gives biologists a convenient means of telling age.
Mountain sheep have eight sharp teeth at the front of the mouth.
These are called incisors and are used to cut off plants. All the teeth are gradually worn down during mastication and this process is accelerated if the diet includes much grit or woody material. The pelage, or coat, of wild sheep is short and coarse, never fine and woolly, as in domestic sheep. In late summer and fall, bighorn sheep, particularly the rams, are beautifully clothed in a rich brown coat with white muzzle, white rump patch, and white trim outlining the back of all four legs. By spring, the brown coat has faded, owing to breakage of the brittle hair tips, to a drab gray-brown.