Wildlife on the Brink: Sierra Nevada Bighorn Sheep

SCIENTIFIC NAME: Ovis canadensis californiana

STATUS: Endangered

HABITAT: Steep, rocky alpine slopes

LIFE HISTORY: Migrates from elevations of approximately 5,000 feet in winter to 11,000 feet or higher in summer. Unable to outrun most predators; stocky build and short legs adapted to flee by climbing.

THREATS: Disease from domestic livestock; excessive predation

FORMER RANGE: Central and southern Sierra Nevada

CURRENT POPULATION: Less than 200

Naturalist John Muir called this stocky sheep "the bravest of all the Sierra mountaineers." The Sierra Nevada Bighorn uses its extraordinary agility to escape predators, scampering up impossibly steep, rocky slopes and bounding from crag to crag.

The bighorn has been less successful, however, in avoiding human hunters and diseases carried by livestock. (Healthy domestic sheep carry strains of bacteria that cause fatal pneumonia in wild bighorn sheep.) In 1998, only 100 adults remained in the Sierra Nevada.

NRDC filed the petition that resulted in the sheep's emergency listing as an endangered species, and worked to close domestic sheep grazing allotments in Sierra National Forest. The bighorn population is still precarious, and NRDC continues to monitor threats to the sheep's survival.

Photo: Sierra Nevada bighorn © CA Dept. Fish & Game