Crotalus ravus, commonly known as the Mexican pigmy rattlesnakeKlauber LM. 1997. Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. 2 volumes. Reprint, University of California Press, Berkeley. . or Mexican pygmy rattlesnake,Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. . is a venomous pit viper species, found only in Mexico. Three subspecies are currently recognized.
Taxonomy A study using mitochondrial DNA strongly suggests that C. ravus is part of a species complex including Crotalus triseriatus, Crotalus pusillus, Crotalus aquilus, and Crotalus lepidus. This study also confirmed strong genetic differentiation among the three subspecies aligning with geographic barriers. A follow-up study using seven nuclear markers places S. ravus basal to all other members of the species complex.
Subspecies SubspeciesTaxon authorCommon nameGeographic rangeC. r. brunneusHarris & Simmons, 1977Oaxacan pygmy rattlesnakeMexico in the highlands of Oaxaca.C. r. exiguusCampbell & Armstrong, 1979Guerreran pygmy rattlesnakeMexico in the Sierra Madre del Sur of central Guerrero.C. r. ravus(Cope, 1865)Central Mexican pygmy rattlesnakeMexico in the Altiplanicie Meridional, including the states of México, Morelos, Tlaxcala, Puebla, and Veracruz.
Description Adults of this species usually grow to a length of , but may reach more than . They are moderately stout in build.
The distinguishing characteristics for the nominate subspecies C. r. ravus include parietal scales that are highly variable in shape and particularly large, less than 3 prefoveals, 21 midbody dorsal scales, 2–4 tail bands and a relatively large rattle.
Distribution Found only in Mexico in the mountains in the center and south of the country, west of the Isthmus of Tehuantepec. Its range includes the southeastern part of the Mexican Plateau in the highlands of Mexico, Morelos, Tlaxcala, Puebla, Veracruz, Oaxaca, and the Sierra Madre del Sur in Guerrero. The type locality given is the "Table land of Mexico." Cochran (1961) interpreted this to be the "south tableland, Veracruz, Mexico."
Campbell and Lamar (2004) describe this species as being found across the Mexican Plateau in the temperate regions of moderate to high elevations. They estimate the vertical distribution to be from about above sea level to a little over altitude.
Conservation Although being listed as of "Least Concern" by the IUCN, C. ravus was listed as "threatened" by the Mexican government in 2010.NOM-059-SEMARNAT-2010, http://dof.gob.mx/nota_detalle.php?codigo=5173091&fecha=30/12/2010
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