Overview

Brief Summary

Common Names

Grand canyon rattlesnake

Arizona black rattlesnake

Midget faded rattlesnake

Southern Pacific rattlesnake

Great basin rattlesnake

Northern Pacific rattlesnake

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Distribution

occurs (regularly, as a native taxon) in multiple nations

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) This species, recently separated from Crotalus viridis, ranges from southern British Columbia to central Baja California, and east to the Rocky Mountains (Pook et al. 2000), Ashton and de Queiroz 2001, Douglas et al. 2002). The ranges and relationships of Crotalus oreganus and Crotalus viridis in the Four Corners region and in northwestern Colorado have not been precisely defined and need further clarification (Hammerson 1999; Brennan and Holycross, 2004, Herpetol. Rev. 35:190-191). Elevational range extends from sea level to around 3,355 meters (11,000 feet) but most localities are below 2,745 meters (9,000 feet) (Basey 1976, Stebbins 2003, Campbell and Lamar 2004).

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Range Description

As defined by Crother et al. (2003), following congruence of Pook et al. (2000), Ashton and de Queiroz (2001), and Douglas et al. (2002), this species encompasses the ranges of all subspecies of traditionally defined C. viridis except viridis and nuntius (i.e., southern British Columbia in western Canada, through the western United States (east to the Rocky Mountains) to central Baja California in Mexico). The ranges and relationships of Crotalus oreganus and Crotalus viridis in the Four Corners region and in northwestern Colorado need further clarification (Hammerson 1999, Brennan and Holycross 2004). The species avoids arid areas such as the Mojave and Colorado Deserts. The elevational range extends from sea level to around 3,355 m asl (11,000 feet) but most localities are below 2,745 m asl (9,000 feet) (Basey 1976, Stebbins 2003, Campbell and Lamar 2004).
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Continent: Middle-America North-America
Distribution: SW Canada, W USA (Washington, California, Oregon ?, Montana),   caliginis: South Coronado Island, off the coast of Baja California  concolor: basins of the Colorado and Green Rivers  helleri: SW California, south into Baja California  lutosus: Great Basin between the Rocky Mountains and the Sierra Nevada.  oreganus: Pacific slopes est of the Cascades and west of the Sierra Nevada, from British Columbia to NE California.
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Southwestern Canada and western USA.

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Physical Description

Type Information

Paratype for Crotalus viridis abyssus
Catalog Number: USNM 78478
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Sex unknown;
Preparation: Dry
Year Collected: 1929
Locality: Grand Canyon, Burro Spring, Navajo, Arizona, United States, North America
  • Paratype: Klauber, L. M. 1930. Trans. San Diego Soc. Nat. Hist. 6 (3): 114, plate 11, figure 1.
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Paratype for Crotalus viridis abyssus
Catalog Number: USNM 59747
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1916
Locality: Grand Canyon, Shinumo Creek, Coconino, Arizona, United States, North America
Elevation (m): 914 to 914
  • Paratype: Klauber, L. M. 1930. Trans. San Diego Soc. Nat. Hist. 6 (3): 114, plate 11, figure 1.
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Paratype for Crotalus viridis abyssus
Catalog Number: USNM 32725
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Preparation: Ethanol
Year Collected: 1903
Locality: Grand Canyon, sand-bar opposite mouth of Bright Angel Creek, Coconino, Arizona, United States, North America
Elevation (m): 732 to 732
  • Paratype: Klauber, L. M. 1930. Trans. San Diego Soc. Nat. Hist. 6 (3): 114, plate 11, figure 1.
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Paratype for Crotalus viridis abyssus
Catalog Number: USNM 78477
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Sex unknown;
Preparation: Dry
Year Collected: 1929
Locality: Grand Canyon, Bright Angel Canyon, Coconino, Arizona, United States, North America
  • Paratype: Klauber, L. M. 1930. Trans. San Diego Soc. Nat. Hist. 6 (3): 114, plate 11, figure 1.
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Ecology

Habitat

Comments: This snake occupies a wide diversity of habitats, from shrubby coastal dunes to timberline, from shrubby basins and canyons to open mountain forests (Nussbaum et al. 1983, Lowe et al. 1986, Brown et al. 1995, Hammerson 1999, Stebbins 2003, Campbell and Lamar 2004). It is primarily terrestrial but sometimes climbs into trees or shrubs. When inactive, it occupies mammal burrows, crevices, caves, or similar secluded sites. Pregnant females may congregate near the winter den until parturition (Ashton and Patton 2001).

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Habitat and Ecology

Habitat and Ecology
This snake occupies a wide diversity of habitats, from shrubby coastal dunes to timberline, from shrubby basins, chaparral and canyons to open mountain forests (Nussbaum et al. 1983, Lowe et al. 1986, Brown et al. 1995, Hammerson 1999, Stebbins 2003, Campbell and Lamar 2004). It avoids very arid areas. It is primarily terrestrial but sometimes climbs into trees or shrubs. When inactive, it occupies mammal burrows, crevices, caves, or similar secluded sites. Pregnant females may congregate near the winter den until parturition (Ashton and Patton 2001).

Systems
  • Terrestrial
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Summer activity range evidently varies geographically; the largest size reported by Macartney et al. (1988) and Ernst (1992) was from California, where the average was 12 ha in males and 6.5 ha in females. Similarly, along the Little Colorado River in Arizona, five radio-tracked individuals for which at least 50 locations were obtained had activity ranges of 4-34 ha (mean = 11.6 ha) minimum convex polygon) (Reed and Douglas 2002). Activity ranges were elongate, corresponding to the canyon bottom, and included both summer and winter habitats.

In Utah, Hirth et al. (1969) found that some individuals move in summer up to about 1.5 km from the winter den.

Gravid females tend to be more sedentary than nongravid individuals. In southern British Columbia, gravid females were sedentary and usually stayed within 50-100 m of the winter den (Macartney 1989).

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Trophic Strategy

Comments: Diet includes mainly small mammals; also birds, lizards, and rarely amphibians (see Ernst 1992). See Diller and Johnson (1988) for predation rate on small mammals in southwestern Idaho. In British Columbia, gravid females generally did not feed (Macartney and Gregory 1988, Macartney 1989); feeding by gravid females has been observed in some areas (e.g., Idaho, Wallace and Diller, 1990, J. Herpetol. 24:246-253). Juveniles in some regions prey mostly on lizards rather than on small mammals.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: This species is represented by a large number (hundreds) of occurrences (subpopulations) (Campbell and Lamar 2004).

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Global Abundance

100,000 to >1,000,000 individuals

Comments: Adult population size is unknown but presumably exceeds 100,000. This snake is fairly common in many areas.

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General Ecology

Mortality tends to be high in first-year young.

May congregate at hibernation dens; formerly many den sites harbored up to several hundred snakes, but most of these populations have been decimated by humans.

Primary predators include humans, various mammalian carnivores, raptors, kingsnakes, whipsnakes, and racers.

The sound emitted from a vibrating rattle is fairly loud and may continue uninterrupted for several minutes in an aroused, fully warmed rattlesnakesnake. Burrowing owls and gophers snakes, which often share mammal burrows with rattlesnakes, produce hissing vocalizations that sound very much like the rattling of a rattlesnake.

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Life History and Behavior

Cyclicity

Comments: These snakes are active mostly in daytime in cool weather but mainly in the evening and at night in hot summer weather (morning and late afternoon in far north). They are active from about April to November over most of the range but in warm climates such as in southern California some may be above ground in any month. At the northern end of the range in southern British Columbia and Idaho most activity occurs from late March or April to early October (Macartney 1989, Wallace and Diller 2001). In southern California, some may be above ground in any month.

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Reproduction

Mating occurs mostly from mid-summer to early fall, occasionally in spring. Young are born August-October (September-early October in Idaho). Litter size increases with female size (average 5 in small subspecies, maximum about 25 in the largest females of the largest subspecies). Individual adult females may not give birth in some years, probably depending on nutritional status; interval between litters was 2 or more years in British Columbia (Macartney and Gregory 1988), probably 2-3 years in southwestern Wyoming (Ashton and Patton 2001); some females from northern Idaho reproduce in consecutive years. In southwestern Idaho, females often gave birth biennially (Diller and Wallace 1996). Individuals require several years (4-6 years in Idaho, 5-7 years [females] in British Columbia) to reach sexual maturity in areas with a short growing season (Macartney and Gregory 1988). Pregnant females may congregate in a small area.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Crotalus oreganus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: N3 - Vulnerable

United States

Rounded National Status Rank: N5 - Secure

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NatureServe Conservation Status

Rounded Global Status Rank: G5 - Secure

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2007

Assessor/s
Hammerson, G.A., Frost, D.R. & Hollingsworth, B.

Reviewer/s
Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, tolerance of a broad range of habitats, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
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Global Short Term Trend: Relatively stable (=10% change)

Comments: Currently, extent of occurrence, area of occupancy, and number of subpopulations probably are relatively stable; population size may be declining but likely at a rate of less than 10 percent over 10 years or three generations.

Global Long Term Trend: Increase of 10-25% to decline of 30%

Comments: Extent of occurrence, area of occupancy, and number of subpopulations probably are relatively stable; population size has declined in many areas in comparison to historical levels (e.g., see Ernst and Ernst 2003).

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Population

Population
This species is represented by a large number (hundreds) of occurrences (subpopulations) (Campbell and Lamar 2004). The adult population size is unknown but presumably exceeds 100,000. This snake is fairly common in many areas, but is very rare in Baja California south of Sierra San Pedro Martir. The extent of occurrence, area of occupancy, and number of subpopulations are probably relatively stable; population size has declined in many areas in comparison to historical levels (e.g., see Ernst and Ernst 2003). Currently, extent of occurrence, area of occupancy, and number of subpopulations are probably relatively stable; population size may be declining but probably at a rate of less than 10% over 10 years or three generations.

Population Trend
Stable
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Threats

Degree of Threat: Medium

Comments: No major threats are known. Locally, populations are being reduced as a result of persecution and habitat loss and degradation from residential, commercial, and agricultural development.

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Major Threats
Overall, this species is not seriously threatened across most of its range. Locally, populations are being reduced as a result of persecution (especially around human settlements) and habitat loss and degradation from residential, commercial, and agricultural development. Populations in Baja California are being impacted by urbanization, agricultural expansion, and the construction of new roads (on which animals made be killed through collision with vehicles).
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Management

Global Protection: Very many (>40) occurrences appropriately protected and managed

Comments: Many occurrences are in protected areas.

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Conservation Actions

Conservation Actions
There are many occurrences in protected areas.
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Relevance to Humans and Ecosystems

Benefits

Economic Uses

Comments: Venomous; human deaths in untreated cases have occurred 18 hours to 5 days after the bite (Ernst 1992); venom of subspecies concolor of eastern Utah and western Colorado is 10-30 times more toxic than that of any other subspecies (Glenn and Straight).

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Wikipedia

Crotalus oreganus

Common names: western rattlesnake,[3] northern Pacific rattlesnake,[4] Pacific rattlesnake,[5] more

Crotalus oreganus is a venomous pit viper 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]

Description[edit source | edit]

The size of this species varies greatly, with some populations being stunted and others growing very large. Mainland specimens often reach 100 cm (39 in) in length, with the largest on record being 162.6 cm (64.0 in) (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 these fade as the animals mature. The color of the iris often matches the ground color, which may be bronze, gold, or different shades of tan, pink, or gray.[3]

Northern Pacific Rattlesnake, near Hood River, Oregon

The color pattern of the typical form, C. o. oreganus, has a dark-brown, dark-gray, olive-brown, or sometimes black or pale yellowish ground color 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, a lateral series of blotches, usually darker than the dorsal blotches, is 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 rings become progressively darker; the last two rings, 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]

Crotalus oreganus on Yosemite Falls


Common names[edit source | edit]

Its common names include 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] and north Pacific rattlesnake.[7]

Geographic range[edit source | edit]

It is found in North America from southwestern Canada, through 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 US, 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 (8,200 ft).[3]

This species also reportedly occurs on six different islands:[3]

Diet[edit source | edit]

Using its heat-sensing facial pits to locate prey, C. oreganus eats birds, bird eggs, and small mammals, from mice up to and including rabbits. It also eats small reptiles and amphibians. The juveniles eat insects.[8]

Reproduction[edit source | edit]

Sexually mature females bear live young in broods of as many as 25.[8]

Conservation status[edit source | edit]

This species is classified as Least Concern on the IUCN Red List of Threatened Species (v3.1, 2001).[9] Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend was stable when assessed in 2007.[10]

Subspecies[edit source | edit]

Subspecies[4]Taxon author[4]Common name[6]Geographic range[6]
C. o. abyssusKlauber, 1930Grand Canyon rattlesnakeThe US in Arizona in the Grand Canyon of the Colorado River, from the north to the south rim
C. o. caliginisKlauber, 1949Coronado Island rattlesnakeMexico, on South Coronado Island, off the northwest coast of Baja California
C. o. cerberus(Coues In Wheeler, 1875)Arizona black rattlesnakeArizona from the Hualpi Mountains and Cottonwood Cliffs in the northwest, southeast to the Santa Catalina, Rincon, Pinaleno and Blue Mountains, Steeple Rock in extreme western New Mexico|-
C. o. concolorWoodbury, 1929Midget faded rattlesnakeColorado and Green River basins of southwestern Wyoming, Utah east of 111°W (excluding the southeastern corner) and extreme east-central Colorado
C. o. helleriMeek, 1905Southern Pacific rattlesnakeSouthern 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, south though Baja California to 28° 30'N
C. o. lutosusKlauber, 1930Great Basin rattlesnakeGreat Basin region, Idaho south of 44°N, Utah west of 111°W, Arizona west and north of the Colorado River, as well as the north rim of the Grand Canyon, 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. oreganusHolbrook, 1840Northern Pacific rattlesnakeFrom the Pacific slope in British Columbia, Canada, south through the United States to San Luis Obispo County and Kern County in California, 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, on Morro Rock off the coast of San Luis Obispo County

See also[edit source | edit]

References[edit source | edit]

  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. 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. ^ a b Hubbs, Brian and Brendan O'Connor. 2012. A Guide to the Rattlesnakes and other Venomous Serpents of the United States. Tricolor Books. Tempe, Arizona. 129 pp. ISBN 978-0-9754641-3-7. (Crotalus o. oreganus, pp. 22-23.)
  9. ^ Crotalus oreganus at the IUCN Red List. Accessed 13 September 2007.
  10. ^ 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.

Further reading[edit source | edit]

  • Holbrook, J.E. 1840. North American Herpetology; or, A Description of the Reptiles Inhabiting the United States. Vol. IV. [First Edition.] Dobson. Philadelphia. 126 pp. (Crotalus oreganus, pp. 115-117.)
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Names and Taxonomy

Taxonomy

Comments: Analysis of historical biogeography based on mtDNA data (Pook et al. 2000) revealed two main clades, one including populations from east and south of the Rocky Mountains and the other consisting of populations west of the Rocky Mountains. The conventionally recognized subspecies do not fully correspond to the phylogenetic pattern, and a review of the systematic status of several populations is needed (Pook et al. 2000).

Ashton and de Queiroz (2001) examined mtDNA variation among 26 populations of C. viridis and also identified two main clades: eastern, including subspecies viridis and nuntius (low levels of genetic divergence), and western, including all other subspecies. However, Ashton and de Queiroz (2001) differed from Pook et al. (2000) with respect to the relationships among members of the western clade, although Ashton and de Queiroz studied only a few individuals from each member of the western clade and stated that the relationships within the western clade are largely unresolved and that none (except possibly cerberus) appeared to deserve recognition as separate evolutionary species. Ashton and de Queiroz suggested that the two main clades be regarded as distinct species, C. viridis (eastern clade) and C. oreganus (western clade). The historical biogeographic scenario described by Ashton and de Queiroz (2001) suggests secondary contact between C. viridis and C. oreganus in northern Arizona, southwestern and northwestern Colorado, and southeastern Utah.

Douglas et al. (2002) examined mtDNA variation in C. viridis, with emphasis on the populations on the Colorado Plateau, as did Pook et al. (2000) and Ashton and de Queiroz (2001). They identified eastern and western clades, with the former including the nominal subspecies viridis and nuntius and the latter encompassing all of the other subspecies. Douglas et al. (2002) argued that all of the western subspecies should be recognized as species, but they did not effectively indicate details of distributional relationships in the contact zones among the proposed species. Douglas et al. (2002) concluded that the taxon nuntius should be regarded as a synonym of viridis.

Crother et al. (2003) considered all of the foregoing evidence and adopted the two-species taxonomy (Crotalus oreganus, Crotalus viridis) that is supported by the congruence among all three studies cited above. Campbell and Lamar (2004) also recognized only the two species. However, further clarification of the distributions of C. viridis and C. oreganus is needed, particularly in the contact zones in northern Arizona, southwestern and northwestern Colorado, and southeastern Utah. For example, populations in northwestern Colorado (Moffat County) identified by Douglas et al. (2002) as C. viridis were mapped as C. oreganus concolor by Campbell and Lamar (2004).

Venom characteristics indicate hybridization between C. viridis and C. scutulatus in New Mexico (Glenn and Straight 1990).

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