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. Once a year, usually about June or July in southern Canada, sheep shed their hair, and until the new coat grows in, they have a scruffy, bedraggled appearance, with patches of matted old hair hanging loosely about them. Lambs make a bleating sound similar to the young of domestic sheep. The only common sound of rams is a nasal snort, usually made as a warning and when rams prepare to fight.
Mountain sheep rely on extremely acute eyesight.
Slight movements and small objects can be detected over a kilometre away. Because on the open mountain expanses an enemy cannot easily approach them unseen, they have little need for highly developed senses of hearing or smell. In Canada, lambs are born between early May and mid-June. Usually one lamb is born per ewe, although twins occur occasionally. Ewes retire from their flock to a secluded gully or canyon to have their lamb, which can readily follow its mother after 2 or 3 days, although somewhat unsteadily.