The Bighorn Sheep originally crossed over the Bering land bridge from Siberia: the population in North America peaked in the millions, and the Bighorn Sheep entered into the mythology of Native Americans. However, the population crashed by 1900 down to several thousand. Conservation efforts (in part, due to the Boy Scouts) has restored the population.
Ovis canadensis is one of three species of mountain sheep in North America and Siberia; the other two species being Ovis dalli, that includes Dall Sheep and Stone's Sheep, and the Siberian Snow sheep Ovis nivicola.
The taxononomy of Ovis canadensis continues to be modified as new genetic and morphologic data becomes available but most scientists currently recognize the following subspecies of bighorn:
In addition, there are currently two federally endangered populations:
Several other prominent Arizonans join the movement and a save the bighorns poster contest was started in schools throughout the state. Burnham provided prizes and appeared in store windows from one end of Arizona to the other. The contest-winning bighorn emblem was made up into neckerchief slides for the 10,000 boy scouts, and talks and dramatizations were given at school assemblies and on radio. The National Wildlife Federation, the Izaak Walton League, and the Audubon Society also joined the effort.
These efforts led to the establishment on of two bighorn game ranges in Arizona: Kofa National Wildlife Refuge and Cabeza Prieta National Wildlife Refuge. On January 18, 1939, over were set aside and a civilian conservation corp side camp was setup to develop high mountain waterholes for the sheep. The Desert Bighorn Sheep is now the official mascot for the Arizona Boy Scouts.
Bighorn Sheep are named for the large, curved horns borne by the males, or rams. Females, or ewes, also have horns, but they are short with only a slight curvature. They range in colour from light brown to grayish or dark, chocolate brown, with a white rump and lining on the back of all four legs. Rocky Mountains bighorn females weigh up to 200 pounds (90 kg), and males occasionally exceed 500 pounds (225 kg). In contrast, Sierra Nevada bighorn females weigh about 140 pounds (63 kg) with males weighing around 200 pounds (90 kg). Males' horns can weigh up to 30 lb (14 kg), as much as the rest of the bones in the male's body.
Bighorn sheep graze on grasses and browse shrubs, particularly in fall and winter, and seek minerals at natural salt licks. Bighorns are well adapted to climbing steep terrain where they seek cover from predators such as coyotes, eagles, and cougars. They live in large herds, but do not have the strict dominance hierarchy of the mouflon: that is, they do not automatically follow a single leader ram, unlike the Asiatic ancestors of the domestic sheep.
Prior to the mating season or "rut", the rams attempt to establish a dominance hierarchy that determines access to ewes for mating. It is during the prerut period that most of the characteristic horn clashing occurs between rams, although this behavior may occur to a limited extent throughout the year. Ram's horns can frequently exhibit damage from repeated clashes. Bighorn ewes exhibit a six-month gestation. In temperate climates, the peak of the rut occurs in November with one, or rarely two, lambs being born in May. The lambs are then weaned when they reach 4-6 months.
Bighorn sheep are highly susceptible to certain diseases carried by domestic sheep such as scabies and pneumonia; additional mortality occurs as a result of accidents involving rock fall or falling off cliffs (a hazard of living in steep, rugged terrain).
Bighorn Sheep are considered good indicators of land health because the species is sensitive to many human-induced environmental problems. In addition to their aesthetic value, Bighorn Sheep are considered desirable game animals by hunters. The Rocky Mountain and Sierra Nevada bighorn occupy the cooler mountainous regions of Canada and the United States. In contrast, the Desert Bighorn Sheep subspecies are indigenous to the hot desert ecosystems of the Southwest United States.
In 1940, Cowan taxonomically split the species into seven subspecies:
However, starting in 1993, Ramey and colleagues, using DNA testing, have shown that this division into seven subspecies is largely illusory. The latest science shows that Bighorn Sheep is one species, with 3 subspecies O. c. canadensis, O. c. nelsoni and O. c. sierrae. O. c. sierrae is a genetically distinct subspecies that only occurs in the Sierra Nevada. O. c. nelsoni occur throughout the southwestern desert regions of the U.S. and Mexico, whereas O. c. canadensis occupy the U.S. and Canadian Rocky Mountains and the northwestern U.S.
Bighorn sheep were once known by the scientific identification argali or argalia due to assumption that they were the same animal as the Asiatic Argali (Ovis ammon). Lewis and Clark recorded numerous sightings of Ovis canadensis in the journals of their exploration--sometimes using the name Argalia. In addition, they recorded the use of bighorn sheep by the Shoshone in making bows. William Clark's Track Map produced after the expedition in 1814 indicates a tributary of the Yellowstone River named Argalia Creek and a tributary of the Missouri River named Argalia River, both in what is today Montana. Neither of these tributaries retained these names however. The Bighorn River another tributary of the Yellowstone, and its tributary stream the Little Bighorn River indicated on Clark's map did retain their names, the latter being the namesake of the Battle of the Little Bighorn.