Photo credit: Terry Spivey
USDA Forest Service
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Length: head and body, 5-6 feet; shoulder height, 2.5-3.5 feet
Habitat: rugged, sparsly wooded mountain slopes
Also known as Mountain Sheep, this heavy-bodied sheep has a remarkable capacity for climbing and jumping thanks to the structure of its hooves.
The wild sheep live far up in the mountains where strong winds gust over the high country. These rugged animals with their spectacular, curved horns are at home in alpine meadow and on rocky slopes out of reach of most predators.
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There are several kinds of bighorn sheep in North America. The northernmost of the wild sheep are the thin horn group including the all-white Dall's sheep of the Arctic and sub-Arctic and the closely related Stone's sheep, which wears darker colors and is native to the northern part of British Columbia and southern Yukon territory. The bighorn group lives to the south and there three kinds commonly recognized, the Rocky Mountain bighorn, The California bighorn and the increasingly rare desert bighorn. Al the North American bighorn sheep are believed to have descended from the wild sheep of northern Asia.
Bighorn sheep carry true horns that continue to grow throughout the animal's life. The male bighorns develop magnificent curling horns, often with a three-quarter curl by the age of four years old. These horns, formed of keratin, grow like fingernails. When food is abundant, as it is during the growing season, the horns grow rapidly. In winter, when the animal may have to draw on its stored fat for energy, the horns grow more slowly.
Bighorn sheep mature by the time they are a year and a half old, but the young ewes seldom begin breeding until they are two and a half. Meanwhile the young rams must work their way into the ram hierarchy, and the older and stronger males with heavier horns keep the young rams away from ewes.
The Rocky Mountain bighorn sheep breeding season comes in November and December and once the mating season ends, the males wander off, leaving the females and young to themselves. Bighorn lambs are born in early summer (a single lamb).
From the high country nursery the wild sheep can keep her vigil, guarding against predators that might threaten her young one. The golden eagle is a threat. If the giant bird casts its shadow over the rocks, the ewe covers her lamb and stands guard. During these early days she feeds the lamb frequently and within a week it has grown strong and sure-footed enough to leave the nursery with its mother when they rejoin their little band of ewes and young.
The bighorn's watch against predators is lifelong. But these animals are well protected by their ability to climb plus the fact that they stay in the open places where they can spot danger from a distance. Although bighorns are killed by coyotes, cougars, lynx, bobcats, wolves and wolverines, their losses to predators are usually low.
Some bighorn sheep are killed in falls, and some are crushed by avalanches. Other succumb to diseases.
CONSERVATION STATUS
But where the habitat is productive, domestic and feral animals are controlled, and hunting is carefully regulated, the wild sheep can maintain their numbers.
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