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Crotalus oreganus

Cladus: Eukaryota
Supergroup: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Reptilia
Subclassis: Diapsida
Infraclassis: Lepidosauromorpha
Superordo: Lepidosauria
Ordo: Squamata
Subordo: Serpentes
Infraordo: Caenophidia
Superfamilia: Viperoidea
Familia: Viperidae
Subfamilia: Crotalinae
Genus: Crotalus
Species: Crotalus oreganus

Crotalus oreganus

Holbrook 1840

Crotalus oreganus is a venomous pitviper species found in North America in the western United States, parts of British Columbia and northwestern Mexico. Seven subspecies are currently recognized, including the nominate subspecies described here.[4]


The size of this species varies greatly, with some populations being stunted and others growing very large. Mainland specimens often reach 100 cm in length, with the largest on record being 162.6 cm (Klauber, 1956)[3] for C. o. oreganus.[6]

This species, in its various forms, shows considerable ontogenetic variation. Juveniles usually have more or less distinct patterns, but this fades as the animals mature. The color of the iris often matches the ground color, which may be bronze, gold, different shades of tan, pink or gray.[3]

The color pattern of the typical form, C. o. oreganus, has a dark brown, dark gray, olive brown, and sometimes black or pale yellowish ground color. This is overlaid dorsally with a series of large dark blotches with uneven white edges. These blotches are also wider than the spaces that separate them. Additionally, there is a lateral series of blotches that are usually darker than the dorsal blotches and clearly visible on all but the darkest specimens. The first rings of the tail are about the same color as the last body blotches, but these become progressively darker; the last two, at the base of the tail, are usually black. The belly is pale yellow, usually with brown spots. A large dark brown blotch on the snout has a pale border behind it that forms transverse bars on the supraoculars. There is a dark brown postocular stripe with a white border that extends from the eye to around the angle of the jaw.[3]

Common names

Western rattlesnake,[3] northern Pacific rattlesnake,[4] Pacific rattlesnake, black rattlesnake, Arizona diamond rattlesnake, black diamond rattlesnake, black snake, California rattlesnake, confluent rattlesnake, diamond-back rattlesnake, Great Basin rattlesnake, Hallowell's rattlesnake, Missouri rattlesnake, Oregon rattlesnake, Pacific rattler, rattlesnake, southern rattlesnake, western black rattlesnake, western rattler,[5] north Pacific rattlesnake.[7]

Geographic range

Found in North America from southwestern Canada, though much of the western half of the United States, and south into northern Mexico. In Canada it is found in southern British Columbia. In the USA it occurs in Washington, Oregon, western and southern Idaho, California, Nevada, Utah, Arizona, and likely west-central New Mexico. In northern Mexico it is found in western Baja California and the extreme north of Baja California Sur, from sea level to an altitude of 2,500 m.[3]

There are also reports of this species occurring on five different islands:[3]

* Morro Rock, Morro Bay, San Luis Obispo County, California (now connected to the mainland by a causeway).
* Anaho Island, Pyramid Lake, Washoe County, Nevada.
* Rattlesnake Island, Clear Lake, Lake County, California (may no longer be found here).
* Santa Catalina Island, California, off the coast of San Pedro, Los Angeles, California.
* South Coronado Island, off the coast of Baja California.

Conservation status

This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2001).[8] Species are listed as such due to their wide distribution, presumed large population, or because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend is stable. Year assessed: 2007.[9]


Subspecies[4] Taxon author[4] Common name[6] Geographic range[6]
C. o. abyssus Klauber, 1930 Grand Canyon rattlesnake The United States, in Arizona in the Grand Canyon of the Colorado river, from the north to the south rim.
C. o. caliginis Klauber, 1949 Coronado Island rattlesnake Mexico, on South Coronado Island, off the northwest coast of Baja California.
C. o. cerberus (Coues In Wheeler, 1875) Arizona black rattlesnake The United States, in Arizona from the Hualpi Mountains and Cottonwood Cliffs in the northwest of the state, southeast to the Santa Catalina, Rincon, Pinaleno and Blue Mountains. Also found at Steeple Rock, in extreme western New Mexico.
C. o. concolor Woodbury, 1929 Midget faded rattlesnake The United States, in the Colorado and Green River basins. This area covers southwestern Wyoming, Utah east of long. 111° West (excluding the southeastern corner) and extreme east-central Colorado.
C. o. helleri Meek, 1905 Southern Pacific rattlesnake The United States in southern California, and Mexico in northern Baja California, west of the desert. In the north from the counties of San Luis Obispo and Kern, and south through the counties of Santa Barbara, Ventura, Los Angeles (including Santa Catalina Island), southwestern San Bernardino, Orange, western Riverside, San Diego and extreme western Imperial. From there its range extends south though Baja California to lat. 28° 30' North.
C. o. lutosus Klauber, 1930 Great Basin rattlesnake The United States in the Great Basin region. Its range includes Idaho south of lat. 44° North, Utah west of long. 111° West, Arizona west and north of the Colorado River as well as the north rim of the Grand Canyon, the entire state of Nevada (excuding Esmeralda, Nye and Clark counties), California east of the Sierra Nevada from Lower Klamath Lake south to below Lake Mono, Oregon south and east of the line Upper Klamath Lake-Fort Rock-Burns-Council (Idaho).
C. o. oreganus Holbrook, 1840 Northern Pacific rattlesnake From the Pacific slope in British Columbia, Canada, south through the United States to San Luis Obispo and Kern counties in California. This includes south-central British Columbia, Washington east of the Cascade Mountains, western Idaho from Coeur d'Alene south to near Council or Weiser, northern and western Oregon (excluding the Cascades), and California west of the Sierra Nevada. Also found on Morro Rock off the coast of San Luis Obispo county.


1. ^ McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
2. ^ Ashton KG, de Queiroz A. 2001. Molecular systematics of the western rattlesnake, Crotalus viridis (Viperidae), with comments on the utility of the d-loop in phylogenetic studies of snakes. Molecular Phylogenetics and Evolution, Vol. 21, No.2, pp. 176-189. PDF at CNAH. Accessed 3 September 2008.
3. ^ a b c d e f g Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
4. ^ a b c d e "Crotalus oreganus". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=209548. Retrieved 28 November 2006.
5. ^ a b Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.
6. ^ a b c Klauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. University of California Press, Berkeley. ISBN 0-520-21056-5.
7. ^ Parker HW, Grandison AGC. 1977. Snakes -- a natural history. Second Edition. British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN 0-8014-1095-9 (cloth), ISBN 0-8014-9164-9 (paper).
8. ^ Crotalus oreganus at the IUCN Red List. Accessed 13 September 2007.
9. ^ 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.

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