|Scientific Name:||Crotalus molossus|
|Species Authority:||Baird & Girard, 1853|
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor/s:||Hammerson, G.A., Vazquez Díaz, J. & Quintero Díaz, G.E.|
|Reviewer/s:||Cox, N., Chanson, J.S. & Stuart, S.N. (Global Reptile Assessment Coordinating Team)|
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.
|Range Description:||The species' range extends from western, central, and southern Arizona, central and southern New Mexico, and southwestern and central Texas in the United States, south through Mexico to the southern edge of the Mexican Plateau and Mesa del Sur (Oaxaca), including Isla Tiburon in the Gulf of California, at elevations from near sea level up to around 2,930 m asl (9,600 feet) (Grismer 2002, Stebbins 2003, Campbell and Lamar 2004).|
Native:Mexico; United States
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||This species is represented by a large number of occurrences (subpopulations). On a range-wide scale, Campbell and Lamar (2004) mapped more than 200 collection sites. The adult population size is unknown but presumably exceeds 100,000. It is common in Mexico and in some areas of the United States. Its extent of occurrence, area of occupancy, number of subpopulations, and population size are probably relatively stable or declining at less than 10% over 10 years or three generations.|
|Habitat and Ecology:||The species' habitat includes rocky areas (rock slides, outcrops, canyon slopes, areas near cliff, stream courses), with vegetation ranging from arid tropical scrub, tropical deciduous forest, mixed boreal-tropical forest, paloverde-cactus-thorn bush associations, oak-grass savanna, and mesquite grasslands to chaparral and the pine-oak and pine-fir belts (Werler and Dixon 2000, Ernst and Ernst 2003, Stebbins 2003, Campbell and Lamar 2004). In Arizona and northern Mexico, this snake often occurs in rocky areas in pine-oak association. A population in southeastern Arizona frequented rocky areas but used arroyos (dry creeks) and creosote bush flats in late summer and autumn (fall) (Beck 1995). Other habitats include creosote bush-covered hills, grassy prairie, giant-dagger flats, and the vicinity of abandoned buildings (Tennant 1984). This species occupies a wide range of habitats in Mexico, where at the southern end of the range habitats include pine-oak, oak savanna, sweet-gum/oak forest, and mesquite grassland (Armstrong and Murphy 1979). Refuges during inactivity include rock crevices, caves, animal burrows, or wood rat houses. This snake is mostly terrestrial but sometimes climbs into trees or bushes.|
|Major Threat(s):||No major threats to this species are known.|
|Conservation Actions:||Many occurrences of this species are in protected areas.|
Armstrong, B.L. and Murphy, J.B. 1979. The natural history of Mexican rattlesnakes. University of Kansas Museum Natural History, Special Publications 1(5): 1-88.
Beck, D.D. 1995. Ecology and energetics of three sympatric rattlesnakes in the Sonoran Desert. Journal of Herpetology 29: 211-223.
Brattstrom, B.H. 1964. Evolution of the pit vipers. Transactions of the San Diego Society of Natural History 13: 185-286.
Campbell, J.A. and Lamar, W.W. 1989. The venomous reptiles of Latin America. Cornell University Press, Ithaca, New York.
Campbell, J.A. and Lamar, W.W. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock, Ithaca, New York and London, UK.
Ernst, C.H. 1992. Venomous Reptiles of North America. Smithsonian Institution Press, Washington, D.C.
Ernst, C.H. and Ernst, E.M. 2003. Snakes of the United States and Canada. Smithsonian Books, Washington, D.C.
Grismer, L.L. 1999. An evolutionary classification of reptiles on islands in the Gulf of California, México. Herpetologica 55(4): 446-469.
Grismer, L.L. 2002. Amphibians and Reptiles of Baja California, Including its Pacific Islands and the Islands in the Sea of Cortés. University of California Press, Berkeley and Los Angeles, California.
IUCN. 2007. 2007 IUCN Red List of Threatened Species. Available at: www.iucnredlist.org. (Accessed: 12th September 2007).
Klauber, L.M. 1972. Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind. Second edition. University of California Press, Berkeley, California.
Lowe, C.H., Schwalbe, C.R. and Johnson, T.B. 1986. The Venomous Reptiles of Arizona. Arizona Game and Fish Department.
Stebbins, R.C. 2003. A Field Guide to Western Reptiles and Amphibians. Third Edition. Houghton Mifflin Company, Boston, Massachusetts.
Tennant, A. 1984. The Snakes of Texas. Texas Monthly Press, Austin, Texas. 561 pp.
Werler, J.E. and Dixon, J.R. 2000. Texas Snakes: Identification, Distribution, and Natural History. University of Texas Press, Austin, Texas.
|Citation:||Hammerson, G.A., Vazquez Díaz, J. & Quintero Díaz, G.E. 2007. Crotalus molossus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 16 April 2014.|