page_title: Bighorn sheep
section_title: Current
hierarchical_section_title: Bighorn sheep / Taxonomy and genetics / Current
caption_attribution_description: English: Female Rocky Mountain bighorn sheep (Ovis canadensis canadensis) in Yellowstone National Park, Wyoming, United States
context_page_description: The bighorn sheep is a species of sheep native to North America. The species is named for its large horns. A pair of horns might weigh up to 14 kg; the sheep typically weigh up to 143 kg. 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 livestock and overhunting.
context_section_description: 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 (about 315–94 thousand years ago). Thus, the three subspecies of O. canadensis are:
  Rocky Mountain bighorn sheep (O. c. canadensis) – occupying the U.S. and Canadian Rocky Mountains, and the Northwestern United States.
  Sierra Nevada bighorn sheep (O. c. sierrae) – formerly California bighorn sheep, a genetically distinct subspecies that only occurs in the Sierra Nevada in California. However, historic observer records suggest that bighorn sheep may have ranged as far west as the California Coastal Ranges which are contiguous to the Sierra Nevada via the Transverse Ranges. An account of "wild sheep" in the vicinity of the Mission San Antonio near Jolon, California and the mountains around San Francisco Bay dates to circa 1769.
  Desert bighorn sheep (O. c. nelsoni) – occurring throughout the desert regions of the Southwestern United States and Northwestern Mexico. The 2016 genetics study suggested more modest divergence of this desert bighorn sheep into three lineages consistent with the earlier work of Cowan: Nelson's (O. c. nelsoni), Mexican (O. c. mexicana), and Peninsular (O. c. cremnobates). These three lineages occupy desert biomes that vary significantly in climate, suggesting exposure to different selection regimens.
  In addition, two populations are currently considered endangered by the United States government:
  Sierra Nevada bighorn sheep (O. c. sierrae),
  Peninsular bighorn sheep, a distinct population segment of desert bighorn sheep (O. c. nelsoni)
caption: Female Rocky Mountain bighorn sheep (O. c. canadensis) in Yellowstone National Park
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