Common names: speckled rattlesnake,Campbell JA, Lamar WW (2004). The Venomous Reptiles of the Western Hemisphere. Ithaca and London: Comstock Publishing Associates. 870 pp. 1,500 plates. . Mitchell's rattlesnake,U.S. Navy (1991). Poisonous Snakes of the World. United States Government. New York: Dover Publications Inc. 203 pp. . white rattlesnakeDitmars RL (1933). Reptiles of the World. Revised Edition. New York: The MacMillan Company. 329 pp. 89 plates.
Crotalus mitchellii is a venomous pit viper species in the family Viperidae. The species is native to the Southwestern United States and adjacent northern Mexico. The species was named in honor of Silas Weir Mitchell (1829–1914), an American medical doctor who also studied rattlesnake venoms.Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. . (Mitchell, S.W., p. 180). Two subspecies are recognized as being valid, including the nominate subspecies described here.
Description Generally, Crotalus mitchellii does not exceed in total length (tail included), with large males measuring between . The race on Isla Ángel de la Guarda is known to become larger, the maximum recorded length for a specimen there being . In contrast, the population on El Muerto Island only reaches a maximum of in length. On the back are about thirty sometimes vague markings often in the form of crossbars. The speckled rattlesnake is sometimes erroneously called the tiger rattlesnake because of these markings. Other times the markings are clearly defined geometric shapes – diamonds, hexagons, hourglasses – which vary in color from snake to snake but are always darker than the ground color. Normally there is a community coloration based on the snakes' specific rock setting. The whole effect: an individual snake looks like it had been formed from granite, a protective coloration it uses with great effect, and that is also quite beautiful when examined, as one might a work of art, against a contrasting background.
Geographic distribution Crotalus mitchellii is found in the southwestern United States and in northwestern Mexico. In the US, its range includes east-central and southern California, southwestern Nevada, extreme southwestern Utah, and western Arizona. In Mexico, it is native in northwestern Sonora and most of Baja California, including Baja California Sur. It also inhabits a number of islands in the Gulf of California, including Angel de la Guarda Island, Carmen, Cerralvo, El Muerto, Espíritu Santo, Monserrate, Piojo, Salsipuedes, and San José, as well as on Santa Margarita Island off the Pacific coast of Baja California Sur.
The type locality is listed as "Cape St. Lucas, Lower California" (Cabo San Lucas, Baja California Sur, Mexico).
Habitat The preferred natural habitat of Crotalus mitchellii is rocky desert and shrubland.
Behavior Crotalus mitchellii is terrestrial, but will sometimes climb into low vegetation.
Reproduction Crotalus mitchellii is ovoviviparous. www.reptile-database.org.
Subspecies and taxonomy SubspeciesTaxon authorCommon nameKlauber LM (1997). Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. First published in 1956, 1972. Berkeley: University of California Press. .Geographic rangeC. m. mitchellii(Cope, 1861)San Lucan speckled rattlesnakeMexico, in Baja California Sur and on the islands of Santa Margarita, Cerralvo, Espíritu Santo, San José, Monserrate, and CarmenC. m. muertensisKlauber, 1949El Muerto Island speckled rattlesnakeMexico, on the island of Isla El Muerto
Grismer (1999) argued that C. m. angelensis and C. m. muertensis should be given species status, mainly due to differences in body size. More recently, Douglas et al. (2007) Douglas ME, Douglas MR, Schuett GW, Porras LW, Thomason BL (2007). "Genealogical concordance between mitochondrial and nuclear DNAs supports species recognition of the Panamint rattlesnake (Crotalus mitchellii stephensi )". Copeia 2007: 920–932. recognised C.m. stephensi as a full species, and Meik et al. (2015) Meik JM, Streicher JW, Lawing AM, Flores-Villela O, Fujita MK (2015). "Limitations of Climatic Data for Inferring Species Boundaries: Insights from Speckled Rattlesnakes". PLoS ONE 10 (6): e0131435. doi:10.1371/journal.pone.0131435 elevated both the southwestern and the Angel de la Guarda speckled rattlesnakes to the state of full species, C. pyrrhus and C. angelensis, whereas the El Muerto Island speckled rattlesnake was considered part of C. pyrrhus
Conservation status The nominate subspecies (Crotalus mitchellii mitchellii) is classified as "Least Concern" on the IUCN Red List of Threatened Species. The population trend was stable when assessed in 2007. 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.
References
Further reading Cope, E.D. (1861). "Contributions to the Ophiology of Lower California, Mexico and Central America". Proceedings of the Academy of Natural Sciences of Philadelphia 13: 292–306. (Caudisona mitchellii, new species, pp. 293–294).
129 pp. (Crotalus mitchelli [sic], pp. 40–41). 240 pp. (Crotalus mitchelli [sic], pp. 206–207). 533 pp., 56 color plates. (Crotalus mitchellii, p. 412 + Plate 51 + Map 193). 1,105 pp. (in two volumes). (Crotalus mitchelli [sic], pp. 974–977, Figure 278 + Map 68 on p. 971).
External links
Crotalus angelensis at San Diego Natural History Museum Crotalus mitchelli at San Diego Natural History Museum Crotalus mitchellii pyrrhus