PENINSULAR BIGHORN SHEEP } Ovis canadensis nelsoni
DESCRIPTION: This sheep is a medium-sized bovid with a muscular body and thick neck. Males range between five and six feet in length and weigh up to 211 pounds; females are smaller, rarely weighing more than 150 pounds. Males have massive horns that spiral outward and forward, while females’ horns never grow larger than one half-spiral. In both sexes, most fur is tan colored; undersides, backs of legs, rump patch, and muzzle are white. Coats shed in patches in June and July.
HABITAT: Peninsular bighorn sheep prefer steep, open slopes, canyons, and washes in hot and dry desert regions where the land is rough, rocky, and sparsely vegetated. Most sheep live between 300 and 4,000 feet in elevation, where average annual precipitation is less than four inches and daily high temperatures average 104 degrees Fahrenheit in the summer.
RANGE: Peninsular bighorn sheep live on dry, rocky, low-elevation desert slopes, canyons, and washes from Palm Springs, California south into Baja California, Mexico.
MIGRATION: Bighorns move throughout their range and return to the same lambing areas year after year. From May through October, they are typically more localized in distribution around permanent water sources.
BREEDING: Ewes and rams reach sexual maturity at roughly two years of age, though rams are unlikely to breed until they are older and larger. Males engage in head-to-head combat to establish dominance. Mating season can last from July to December, with most births taking place from late February to May. Typically, ewes give birth to one lamb — twins are rare — with gestation lasting from 150 to 180 days. About a third of lambs do not survive their first summer due to harsh conditions and mountain lion predation.
LIFE CYCLE: Within weeks of birth, lambs are eating native grasses; at four to six months of age, they are weaned. Ewes and lambs tend to graze together, separate from rams, until breeding season. At two to four years of age, young rams follow adult rams away from their birth group during the fall breeding period. Peninsular bighorn sheep can live for 10 to 15 years.
FEEDING: Sheep graze on a wide variety of plant species. Green, succulent grasses and forbs are preferred, though shrubs and herbaceous annuals and perennials comprise most of their diet, supplemented with some cacti and grasses.
THREATS: Loss of habitat due to development and agriculture, collisions with cars, predation by mountain lions, and diseases contracted from domestic sheep caused Peninsular bighorn sheep to decline.
POPULATION TREND: Populations plummeted from 971 in 1971 to 276 in 1996, but since being listed as endangered in 1998, the number of bighorns has increased to 705.