Crotalus Helleri

''Crotalus helleri'', known as the Southern Pacific rattlesnake, black diamond rattlesnake, Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing Associates, a division of Cornell University Press. (7th printing, 1985). 1,105 pp. (in two volumes). . (''Crotalus viridis helleri'', pp. 1014–1018, Figure 290 + Map 67 on p. 951). and by other names, is a pit viper subspecies found in southwestern California and south into Baja California, Mexico, that is known for its regional variety of dangerous venom types.

Etymology

The specific name, ''helleri'', is in honor of American zoologist Edmund Heller.

Description

Adults are 24–55 inches (61–139 cm) in length.

The color pattern consists of a pale brown, gray-brown, or yellowish brown ground color overlaid with a series of large, dark brown dorsal blotches that may or may not have pale centers.Campbell JA, Lamar WW (2004). ''The Venomous Reptiles of the Western Hemisphere''. 2 volumes. Ithaca and London: Comstock Publishing Associates. 870 pp., 1500 plates. . The blotches are more diamond shaped, as opposed to those of '' C. o. oreganus'' that are more hexagonal, and are bordered by light scales. The tail rings are not clearly defined. Behler JL, King FW (1979). ''The Audubon Society Field Guide to North American Reptiles and Amphibians''. New York: Alfred A. Knopf. 743 pp. LCCCN 79-2217. . (''Crotalus viridis helleri'', pp. 694–695 + Plate 627). In juveniles, the end of the tail is bright orange, but this turns to brown as the snakes mature. In adults, the base of the tail and the first segment of the rattle are brown. The postocular stripe is moderately to very clearly defined. In juveniles, this stripe is bordered above by a pale stripe, but as the snakes mature this turns to drab yellow or brown. A conspicuous pale crossbar is sometimes present across the supraoculars, after which the head is a uniform dark color. In some older snakes the head is mostly dark with almost no trace of the supraorbital crossbar, or none at all.

Common names

Common names include Southern Pacific rattlesnake, black diamond rattlesnake, black (diamond) rattler, gray diamond-back, mountain rattler, Pacific rattler, and San Diegan rattler.

Venom varieties

Some populations of ''Crotalus helleri'' have a neurotoxic venom that is very similar to the extremely dangerous Mojave rattlesnake (the "Mojave Green") toxin in the way it attacks the nervous system. Other populations can have hemotoxic and myotoxic venom that is more typical among rattlesnakes and though less dangerous, can also can give a fatal bite.
Thus, depending on where the bite was sustained, envenomation from this snake can require a much higher dose of Crotalidae polyvalent immune fab ("Crofab"), an antivenom used to treat the bite of North American pit vipers, than the venoms of other rattlesnakes, including the venom of ''Crotalus helleri'' specimens of different provenance. In a survey of various populations of ''Crotalus'' in California, every sampled specimen with disabling neurotoxic venom had originated near Idyllwild, California, in the San Jacinto Mountains. Scientists considered the intraspecific variety of venom types "medically significant", while hypothesizing that evolutionary pressures, driven by regional habitat differences and the associated challenges of hunting prey in each, could have been behind the variation of venom types in ''Crotalus helleri'', and that cross-breeding with the Mojave rattlesnake, which is geographically separated from neurotoxic ''Crotalus'' populations, was unlikely.

Geographic range

This snake is found in the United States in southern California, and in Mexico in northern Baja California, west of the desert. In the north it is found from the counties of San Luis Obispo and Kern, and south through the counties of Santa Barbara, Ventura, Los Angeles (including Santa Catalina Island and the foothills.), southwestern San Bernardino, Orange, western Riverside, San Diego and extreme western Imperial. From there its range extends south through Baja California to lat. 28° 30' North. Klauber LM (1997). ''Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind''. Second Edition. First published in 1956, 1972. Berkeley, California: University of California Press. 1,476 pp. (in two volumes). . According to Klauber (1956), the type locality is "San Jose, Lower California" an José, lat. 31° N, Baja California (state), Mexico McDiarmid RW, Campbell JA, Touré T (1999). ''Snake Species of the World: A Taxonomic and Geographic Reference, Volume 1''. Washington, District of Columbia: Herpetologists' League. 511 pp. (series). (volume).

References

Further reading

*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'' 21 (2): 176–189
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CNAH
Accessed 12 December 2007.
*Hubbs B, O'Connor B (2012). ''A Guide to the Rattlesnakes and other Venomous Serpents of the United States''. Tempe, Arizona: Tricolor Books 129 pp. . (''Crotalus oreganus helleri'', pp. 25–27).
* Meek SE (1905). "An Annotated list of a Collection of Reptiles from Southern California and Northern Lower California". Field Columbian Museum Publication 104. ''Fieldiana Zoology'' 7 (1): 1–19. ("''Crotalus helleri'' sp. nov.", pp. 17–18 & Plate II).

External links

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{{Taxonbar, from1=Q102111516, from2=Q5188960

helleri
Reptiles of Mexico
Reptiles of the United States
Fauna of California
Fauna of the Baja California Peninsula
Fauna of the Western United States
Fauna of the California chaparral and woodlands
Natural history of the Peninsular Ranges
Natural history of the Transverse Ranges
Animals described in 1905