Crotalus oreganus concolor

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Crotalus oreganus concolor
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Genus: Crotalus
C. o. concolor
Trinomial name
Crotalus oreganus concolor
Woodbury, 1929
  • Crotalus concolor
    Woodbury, 1929
  • Crotalus confluentus decolor Klauber, 1930
  • Crotalus confluentus concolor – Woodbury, 1930
  • Crotalus viridis concolor
    – Klauber, 1936
  • Crotalus viridis decolor
    Gloyd, 1940
  • Crotalus viridis decolor
    – Klauber, 1956
  • Crotalus viridis concolor
    – Klauber, 1972[1]
  • Crotalus oreganus concolor
    – Ashton & de Queiroz, 2001[2]
Common names: midget faded rattlesnake, yellow rattlesnake, faded rattlesnake.[3]

Crotalus oreganus concolor is a venomous pit viper subspecies[4] found in the western United States. It is a small subspecies known for its faded color pattern.


Grows to a maximum length of 750 mm (29 12 in). The smallest gravid female measured was 522 mm (20 12 in).[5]

The color pattern consists of a pinkish, pale brown, yellow-brown, straw-colored, reddish or yellow-brown ground color, overlaid with a series of brown elliptical or rectangular dorsal blotches. However, most specimens are gray or silvery. In juveniles the pattern is distinct, but becomes faded in adults, almost to the point where it is indistinguishable from the ground color.[6]

Geographic range[edit]

Found in 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 west-central Colorado.[5] The type locality given is "King's Ranch, Garfield Co., at the base of the Henry Mts [Utah]."[1]


This subspecies possesses the most toxic venom of the C. oreganus / C. viridis group, although there is apparently considerable variability among local populations (Glenn and Straight, 1977, 1978). It is even one of the most potent venoms found in North America (Glenn and Straight, 1977), and according to LD50 studies the venom is many times more potent than that of an Asiatic Cobra,[7] it is characterized by the presence of a presynaptic neurotoxin, referred to as concolor toxin, the amount of which varies in individual snakes (Glenn and Straight, 1977, 1990; Wetstein et al., 1985).[6]

See also[edit]


  1. ^ a b 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. ^ Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.
  4. ^ "Crotalus oreganus concolor". Integrated Taxonomic Information System. Retrieved 11 August 2007.
  5. ^ a b Klauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. 2 volumes. Reprint, University of California Press, Berkeley. ISBN 0-520-21056-5.
  6. ^ a b 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.
  7. ^

Further reading[edit]

  • 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 oreganus concolor, pp. 32–33.)
  • Woodbury, Angus M. 1929. A new rattlesnake from Utah. Bull. Univ. Utah 20 (1).

External links[edit]