Rocky Mountain bighorn sheep
| Bighorn sheep Temporal range: 0.7–0 Ma Early – Recent |
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| Male (ram) bighorn sheep | |
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| Captive female (ewe) bighorn sheep | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Family: | Bovidae |
| Subfamily: | Caprinae |
| Genus: | Ovis |
| Species: | O. canadensis |
| Binomial name | |
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Ovis canadensis Shaw, 1804 |
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| Bighorn sheep range | |
| Synonyms | |
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O. cervina Desmarest |
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O. cervina Desmarest
O. montana Cuvier
The bighorn sheep (Ovis canadensis) is a species of sheep native to North America named for its large horns. These horns can weigh up to 14 kilograms (30 pounds), while the sheep themselves weigh up to 140 kg (300 lb). Recent genetic testing indicates three distinct subspecies of Ovis canadensis, one of which is endangered: O. c. sierrae. Sheep originally crossed to North America 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. By 1900, the population had crashed to several thousand, due to diseases introduced through European and overhunting.
Ovis canadensis is one of three species of mountain sheep in North America and Siberia; the other two species being Ovis dalli, which includes Dall sheep and Stone's sheep, and the Siberian snow sheep, Ovis nivicola. Wild sheep crossed the Bering land bridge from Siberia into Alaska during the (about 750,000 years ago) and subsequently spread through western North America as far south as Baja California and northwestern mainland Mexico. Divergence from their closest Asian ancestor (snow sheep) occurred about 600,000 years ago. In North America, wild sheep diverged into two extant species—Dall sheep, which occupy Alaska and northwestern Canada, and bighorn sheep, which range from southern Canada to Mexico. However, the status of these species is questionable given that hybridization has occurred between them in their recent evolutionary history.
In 1940, Ian McTaggart-Cowan split the species into seven subspecies:
However, starting in 1993, Ramey and colleagues, using DNA testing, have shown this division into seven subspecies is largely illusory. Most scientists currently recognize three subspecies of bighorn. This taxonomy is supported by the most extensive genetics (microsatellite and mitochondrial DNA) study to date (2016) which found high divergence between Rocky Mountain and Sierra Nevada bighorn sheep, and that these two subspecies both diverged from desert bighorn prior to or during the Illinoian glaciation (~315–94 thousand years ago [kya]). Thus the three subspecies of Ovis canadensis:
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Wikipedia