Bighorn Sheep (Ovis canadensis) Fact Sheet: Taxonomy & History

Taxonomy

• Carl Linnaeus described the genus Ovis in his 1766 taxonomy
• Official description and naming did not occur until 1804, although an American wild sheep was recorded by the Spanish explorer Coronado in 1540
• Recent taxonomies
  • Subspecies designations are still debated, as evidence from genetic and morphological studies conflict (Buchalski et al. 2016)
  • One species and seven subspecies recognized according to Integrated Taxonomic Information System (2017)
  • Buchalski et al. (2016) differentiated five genetic clusters of desert southwest bighorn sheep (not including O. c. californiana)
  • Subsequent genetic studies have not been able to established a consensus on the number of sub-species. Mitochondrial DNA analysis by Boyce et al (1999), indicate that the multiple ewe subpopulations existing within the Peninsular area are basic genetic units.
• Previous taxonomies
  • Cowan’s 1940 nomenclature of North American mountain sheep recognizes 2 species: Thinhorn sheep (Ovis dalli) and Bighorn sheep (Ovis canadensis). Seven subspecies of mountain sheep are listed: auduboni, californiana, canadensis, cremnobates, mexicana, nelsoni, weemsi
  • Genetic studies by Ramey and Wehausen (1993) indicate that major revisions are needed to Cowan’s taxonomy. They synonymized nelsoni and cremnobates adopting the oldest name for the subspecies, Ovis canadensis nelsoni.

Common Names

• “Desert bighorn” is an arbitrary term used for the bighorns inhabiting the arid, sparsely vegetated desert environment of the extreme western and southwestern parts of the U.S. and northern Mexico (cremnobates, mexicana, nelsoni, and weemsi). These sheep are also referred to by regional names: Arizona Bighorn, Mexican Bighorn.
• "Peninsular bighorn" has been used recently to refer to the combined populations of cremnobates and nelsoni (a synonomy suggested in 1993)
• “Mountain bighorn” is a common term for the northern subspecies: canadensis and californiana. They also have regional common names: Rocky Mountain Bighorn, California Bighorn
• All subspecies may be referred to as “Bighorns” or “Mountain Sheep”

• The ancestors of bighorn sheep resided in the mountain and desert regions of Eurasia from early Pleistocene.
• Crossing the Bering land bridge during the late Pleistocene (100,000 years ago), they spread to mountains of Europe, North Africa, Asia and North America.
• First sheep into New World were believed to be similar to the argali of the Asiatic steppes
• The old world sheep evolved into an incredible number of new and distinct species as they adapted to a variety of habitats. (There are some 36-40 races or subspecies of wild sheep today)
• True goats (Capra) are closest relatives. Unlike goats, sheep have preorbital and inguinal glands and lack an odoriferous tail gland. They have interdigital glands on all four feet.

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia (mammals) (Linnaeus, 1758)

Order: Artiodactyla* (or Cetartiodactyla) (even-toed hoofed animals: includes pigs, sheep goats, cattle, deer) (Owen 1848)

Family: Bovidae (buffalo, cattle, sheep, goats) (Gray, 1821)

Subfamily: Caprinae (goats, sheep) (Gray, 1821)

Genus: Ovis (sheep, mouflons, urial, argali, bighorn, thin horns snow sheep, Dall's sheep) (Linnaeus, 1758)

Species: Ovis canadensis (Shaw, 1804) - bighorn sheep

Subspecies: O. c. auduboni (Merriam, 1901)
Subspecies: O. c. californiana (Douglas, 1829) - California bighorn sheep
Subspecies: O. c. canadensis (Shaw, 1804) - Rocky Mountain bighorn sheep
*Subspecies: O. c. cremnobates (Elliot, 1904) - Peninsular bighorn sheep
Subspecies: O. c. mexicana (Merriam, 1901) - desert bighorn sheep
*Subspecies: O. c. nelsoni (Merriam, 1897) - Nelson's/Nelson bighorn sheep, Peninsular bighorn sheep, desert bighorn sheep
Subspecies: O. c. weemsi (Goldman, 1937)

*Wehausen and Ramey (1993) synonymized O. c. crenobates and O. c. nelsoni.

Describer: Shaw (1804). The Canadian Sheep. Plate 610, the description and the index in The Naturalist’s Miscellany (by G. Shaw and E. Nodder), Vol 15. Nodder and Co., London.

Sources: Integrated Taxonomic Information System (2017)

**New anatomical and DNA evidence on the relationship between Artiodactyla (even-toed ungulates) and Cetacea (whales and dolphins) recently led to a merging of the two orders into a new group, Cetartiodactyla (Montgelard, 1997; reviewed in Kulemzina, 2009). As of October 2012, experts had not agreed on whether to define Cetartiodactyla as an official taxonomic order that would replace Artiodactyla and Cetacea. Some continue to list okapi in the order Artiodactyla (Franklin, 2011) or use the term Cetartiodactyla without defining it as an order (IUCN, 2008).

McKenna (1997)
Hall (1981)
Valdez (1999)
USFWS (2000)
Young & Manville (1960)
Ramey & Wehausen (1993)
Shackleton (1985)
Geist (1971)
Boyce et al. (1999)