BIGHORN, the common name of the Rocky Mountain sheep (Ovis cervina), so called from the size of the horns in the male. The female bears shorter, ribbed horns. The bighorn is the only wild sheep indigenous to the New World, where it was formerly found from Mexico to Alaska in the mountainous districts; it is now extremely rare south of Montana, except in game preserves. The bighorn is gregarious and displays great activity and wari ness. The horns of the ram may measure 42in. round the curve. There are several varieties, sometimes separated as dis tinct species. (See SHEEP.)