western rattlesnake (Phoenix Zoo - Arizona Trail)

western rattlesnake

Crotalus oreganus

Summary ⁷

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.

Range description ⁸

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).

Iucn red list assessment ⁹

Red List Category

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.