bighorn

Bighorn, river, United States

Bighorn, river, 461 mi (741 km) long, formed in W central Wyo. by the confluence of the Wind and Pop Agie rivers and flowing north to join the Yellowstone River in S Mont. The Bighorn basin, part of the Missouri River basin project, has several dams that provide for flood control, irrigation, hydroelectricity, and recreation. Boysen and Yellowtail are the principal dams; the lake behind Yellowtail dam is the nucleus of Bighorn Canyon National Recreation Area (see National Parks and Monuments, table). In 1807 a U.S. trading post was established at the mouth of the Bighorn. The battle between the forces of Col. George Custer and the Sioux took place (1876) near the junction of the Bighorn and the Little Bighorn rivers.

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bighorn, in zoology

bighorn or Rocky Mountain sheep, wild sheep of W North America, formerly plentiful in mountains from Canada to Mexico. Indiscriminate hunting, disease, and scarcity of food have reduced its numbers, and in some areas it has been exterminated. It is a heavy, grayish brown animal, with a conspicuous whitish patch on its hindquarters; the male has heavy, curling horns, while the female has short, straight spikes. One type of bighorn lives at high altitudes in the W United States and another in desert regions. Alaskan types are the Dall's, or white, sheep and the Stone's, or black, sheep. Bighorn sheep are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Artiodactyla, family Bovidae.

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bighorn

 or mountain sheep

Bighorn sheep (Ovis canadensis).

(credit: Harry Engels—The National Audubon Society Collection/Photo Researchers)

Stocky, climbing hoofed mammal (Ovis canadensis) of western North America. Both sexes have horns that in the male may curve in a spiral more than 39 in. (1 m) long. Their fur is usually brown with a whitish rump patch. The related thinhorn, or Dall's sheep (O. dalli), of Alaska and Canada is similar to the bighorn. Both species are about 39 in. (1 m) tall at the shoulder, but the bighorn is heavier, weighing up to 300 lb (136 kg). They live in small groups among remote crags and cliffs of mountainous areas and feed mainly on grasses. Bighorn rams compete for females by launching themselves at each other from a few yards' distance and clashing horns.