|Crotalus horridus, timber rattlesnake|
Crotalus is a genus of venomous pit vipers in the family Viperidae, known as rattlesnakes or rattlers. The genus is found only in the Americas from southern Canada to northern Argentina, and member species are colloquially known as rattlesnakes. The generic name Crotalus is derived from the Greek word κρόταλον krótalοn, which means "rattle" or "castanet", and refers to the rattle on the end of the tail which makes this group (genera Crotalus and Sistrurus) so distinctive. Currently, 32 to 45 species are recognized as being valid.
Members of the genus Crotalus range in size from only 50–70 centimetres (20–28 in) (C. intermedius, C. pricei), to over 150 centimetres (59 in) (eastern and western diamondback rattlesnakes). In general, adult males are slightly larger than females. Compared to most snakes, they are heavy-bodied, although some African vipers are much thicker. Most forms are easily recognized by the characteristic rattle on the end of their tails, although a few island populations form exceptions to this rule: C. catalinensis has lost its rattle entirely, Crotalus lorenzoensis usually has no rattle, and both Crotalus ruber lucasensis and Crotalus estebanensis exhibit a tendency for rattle loss. The rattle may also be lacking in any species due to a congenital abnormality.
The rattle consists of a series of loosely interlocking hollow shells, each of which was at one point the scale covering the tip of the tail. In most other snakes, the tail tip, or terminal spine, is cone-shaped, hardly any thicker than the rest of the skin, and is shed along with it at each successive molt. In this case, however, the end-scale, or "button", is much thicker and shaped like a bulb, with one or two annular constrictions to prevent it from falling off. Before each molt, a new button will have developed inside the last one and before the skin is shed off its body, the tip of new button shrinks, then loosening the shell of the previous one. This process continues so the succession of molts produces an appendage consisting of a number of interlocking segments that make an audible noise when vibrated. Since younger specimens may shed three or four times in a year, every time adding a new segment to the rattle, the number of segments bears no relation to the age of the snake. In theory, the rattle could become very long indeed, but in practice, the older segments tend to wear out and fall off. How quickly this happens depends on the snake's environment, but end segments tend to break off after the rattle becomes about six or seven segments long; it is uncommon to find specimens with as many as a dozen segments. In captive specimens, however, as many as 29 segments have been found.
Distribution and habitat
No species of Crotalus is considered aggressive; when threatened, most retreat quickly. However, most species defend themselves readily when cornered.
How far these snakes can strike has been controversial. Obviously this depends on the size of the animal, but other factors may also play a role, such as the species, the position of the body, and the degree of excitement. Additionally, the question of definition exists: from which point on the snake should a strike be measured: from the front, the middle, or the back of the anchor coil on the ground? Even if the length of the specimen is known, once it strikes, it is almost impossible to determine the limiting point reached by its head and the position of its body when the movement started. Therefore, it is not surprising that many conflicting statements can be found in the available literature about how far these snakes can strike. Estimates have been given that range from one-third of the body length, to half, three-quarters or even the full length of the animal. They rarely strike further than half of their body length, and almost never more than three-fourths, but it is still not wise to trust such values if only because it is not possible to accurately judge the length of a coiled snake.
The diets of species of Crotalus generally consist of vertebrates, although many invertebrate species have also been consumed. Smaller species feed mainly on lizards, while larger species start by feeding on lizards as juveniles and then switch to preying mainly on mammals as adults. Prey items more frequently taken include rabbits, ground squirrels, tree squirrels, chipmunks, prairie dogs, gophers, and rats and mice, while those less frequently taken include birds, snakes, and amphibians. Cannibalism has been reported in a number of different species. Individuals that feed on rodents usually release their prey after a strike, and these snakes evidently can discriminate between trails left by prey that has or has not been envenomated.:506
For all species of Crotalus, the most significant threats come from people, but they also face many natural enemies. These include other snakes, such as kingsnakes (Lampropeltis), coachwhips (Masticophis), indigo snakes (Drymarchon) and racers (Coluber), birds, such as hawks, eagles, owls, roadrunners, and ravens, and mammals, such as coyotes, foxes, wildcats, badgers, skunks and pigs. Certain species of birds frequently prey on these snakes, but this is not without risk. Two cases were reported in which dead hawks found near venomous snakes had suffered hemorrhage and gangrenous necrosis due to snakebite.:514
The genus Crotalus is ovoviviparous, giving birth to live young. The basic lifecycle of many Nearctic species has been known for quite some time. Females at an age of 26 months undergo vitellogenesis as they enter their third hibernation, mate the following spring, and give birth later in September or October.:516
A number of variations to this basic cycle occur. In North America, the females of some species store sperm in their oviducts for at least eight months, and the males (all species of which undergo spermatogenesis during the summer) store sperm in the vas deferens for at least a year. Thus, species that store sperm for a shorter duration mate in the spring and store sperm in the vas deferens, while those that do so for a longer duration mate in the fall and store sperm in the oviduct over the winter, after which fertilization occurs the following spring.:516 In addition, species that occur further north, where it is colder during much of the year and the feeding and growing season is short, may reproduce only every other year or less. Those found in central and southern Mexico or the tropics have reproductive cycles that correspond mostly with the rainy season.:519
Two main hemotoxic effects are caused by rattlesnake venom. First, zinc-containing metalloproteases act upon capillary endothelial cells to cause platelet aggregation and hemorrhage. Second, the platelet antagonist crotalin creates a severe bleeding effect as it binds to the surface proteins, blocking aggregation. These two starkly different effects may seem counterproductive, but the effect should be profound. Firstly, endothelial-cell disruption causes lysis and internal bleeding. Then, as these hemorrhages increase, the natural thrombin response is hindered by the effect of crotalin increasing the toxic effect. Their observed hunting technique is a bite-and-release method, so a fast-acting toxin would be ideal. Assuming the natural median prey would be a small rodent such as a mouse, the bite would elicit a fear response, quickening heart rate and increasing blood pressure. This would speed the toxic effect, as well as spread the hemolytic and hemorrhagic effects.
|Image||Species||Taxon author||Subsp.*||Common name||Geographic range|
|C. adamanteus||Palisot de Beauvois, 1799||0||Eastern diamondback rattlesnake||The southeastern United States from southeastern North Carolina, south along the coastal plain through peninsular Florida to the Florida Keys, and west along the Gulf Coast through southern Mississippi to southeastern Louisiana|
|C. angelensis||Klauber, 1963||0||Angel de la Guarda Island speckled rattlesnake||Isla Ángel de la Guarda in the Gulf of California, Mexico|
|C. aquilus||Klauber, 1952||0||Querétaro dusky rattlesnake||The highlands of central Mexico: Guanajuato, Hidalgo, State of Mexico, Michoacán, and San Luis Potosí|
|C. armstrongi||Campbell, 1979||0||Western dusky rattlesnake||Mexico: Jalisco and Nayarit|
|C. atrox||Baird & Girard, 1853||2||Western diamondback rattlesnake||The Southwestern United States from central Arkansas and southeastern California, south into Mexico as far as northern Sinaloa, Hidalgo, and northern Veracruz, disjunct populations in southern Veracruz and southeastern Oaxaca|
|C. basiliscus||(Cope, 1864)||0||Mexican west coast rattlesnake||Western Mexico from southern Sonora to Michoacán|
|C. campbelli||Bryson, Linkem, Dorcas, Lathrop, Jones, Alvarado-Diaz, Grünwald & Murphy, 2014||0||Campbell's rattlesnake||Mexico: western Jalisco, northwestern Colima|
|C. catalinensis||Cliff, 1954||0||Santa Catalina rattlesnake||Isla Santa Catalina in the Gulf of California (western Mexico)|
|C. cerastes||Hallowell, 1854||3||Sidewinder,
|The southwestern United States in the desert region of eastern California, southern Nevada, extreme southwestern Utah, and western Arizona, northwestern Mexico in western Sonora and eastern Baja California|
|C. cerberus||(Coues, 1875)||0||Arizona black rattlesnake||Central Arizona to western New Mexico|
|C. concolor||(Woodbury, 1929)||0||Midget faded rattlesnake||basins of the Colorado and Green rivers in the United States|
|C. culminatus||Klauber, 1952||0||Northwestern neotropical rattlesnake||Mexico in southwestern Michoacán, southern and western Morelos, Guerrero, and southwestern Oaxaca, probably in extreme western Puebla and possibly in the Mexican Federal District|
|C. durissus||Linnaeus, 1758||7||South American rattlesnake||All South American countries except Chile and Ecuador (although the various populations are disjunct), some islands in the Caribbean|
|C. ehecatl||Carbajal-Marquez, Cedeno-Vazquez, Martinez-Arce, Neri-Castro, & Machkour-M’rabet, 2020||0||Tehuantepec Isthmus Neotropical rattlesnake||Mexico: (Chiapas, Oaxaca)|
|C. enyo||(Cope, 1861)||3||Baja California rattlesnake||Western Mexico on the Baja California Peninsula from around Río San Telmo on the west coast and from opposite Isla Ángel de la Guarda on the Gulf Coast, south to Cabo San Lucas, on the following islands in the Gulf of California: San Marcos, Carmen, San José, San Francisco, Partida del Sur, Espírita Santo, and Cerralvo, off the Pacific coast on Isla Santa Margarita|
|C. ericsmithi||Campbell & Flores-Villela, 2008||0||Guerreran long-tailed rattlesnake||Western Mexico: Guerrero|
|C. estebanensis||Klauber, 1949||0||San Esteban Island rattlesnake||Mexico: Isla San Esteban (Gulf of California)|
|C. helleri||(Meek, 1905)||0||Southern Pacific rattlesnake||SW California, Baja California, Mexico|
|C. horridusT||Linnaeus, 1758||0||Timber rattlesnake||The eastern United States from southern Minnesota and southern Maine, south to east Texas and north Florida, in southern Canada in southern Ontario|
|C. intermedius||Troschel, 1865||3||Mexican small-headed rattlesnake||Central and southern Mexico, in southeastern Hidalgo, southern Tlaxcala, northeastern and south-central Puebla, west-central Veracruz, Oaxaca, and Guerrero|
|C. lannomi||W. Tanner, 1966||0||Autlán rattlesnake||Western Mexico in Jalisco|
|C. lepidus||(Kennicott, 1861)||4||Rock rattlesnake||The southwestern United States in Arizona, southern New Mexico, and southwestern Texas, south into north-central Mexico|
|C. lorenzoensis||Radcliffe & Maslin, 1975||0||San Lorenzo Island red diamond rattlesnake||Mexico, San Lorenzo Island in the Gulf of California|
|C. lutosus||(Klauber, 1930)||0||Great Basin rattlesnake||Great Basin between the Rocky Mountains and the Sierra Nevada|
|C. mictlantecuhtli||Carbajal-Marquez, Cedeno-Vazquez, Martinez-Arce, Neri-Castro, & Machkour-M’rabet, 2020||0||Veracruz Neotropical rattlesnake||Mexico: (Veracruz)|
|C. mitchellii||(Cope, 1861)||2||Speckled rattlesnake||Mexico: most of Baja California Sur and on a number of islands in the Gulf of California and on Isla Santa Margarita off the Pacific coast of Baja California Sur|
|C. molossus||Baird & Girard, 1853||3||Black-tailed rattlesnake||The southwestern United States (Arizona, south-western New Mexico), and Mexico from Sonora and western Chihuahua as far south as Oaxaca, in the Gulf of California on San Esteban Island and Tiburón Island|
|C. morulus||Klauber, 1952||0||Tamaulipan rock rattlesnake||Mexico (Sierra Madre Oriental: Tamaulipas, Nuevo León, Coahuila)|
|C. oreganus||Holbrook, 1840||0||Western rattlesnake||Southwestern Canada (southern British Columbia), south though the northwestern half of the United States (Washington, Oregon, western and southern Idaho, California|
|C. ornatus||Hallowell, 1854||0||Eastern black-tailed rattlesnake||The southwestern United States (New Mexico, western and central Texas) and north-eastern Mexico (Chihuahua, Coahuila)|
|C. polisi||Meik, Schaack, FloreS-Villela, & Streicher, 2018||0||Horsehead Island speckled rattlesnake||Cabeza de Caballo Island, Baja California, Mexico|
|C. polystictus||(Cope, 1865)||0||Mexican lance-headed rattlesnake||Central Mexican Plateau, from southern Zacatecas and northeastern Colima east to east-central Veracruz|
|C. pricei||Van Denburgh, 1895||2||Twin-spotted rattlesnake||In the US from southeastern Arizona, and Mexico in northern Sonora southeast through Chihuahua, Durango, southeastern Coahuila and Nuevo León into Tamaulipas|
|C. pusillus||Klauber, 1952||0||Tancitaran dusky rattlesnake||West-central Mexico in southwestern and west-central Michoacán and adjacent Jalisco, probably also in northeastern Colima|
|C. pyrrhus||Cope, 1867||0||Southwestern speckled rattlesnake||Southwestern United States (western Arizona, southern California, southern Nevada, extreme south-western Utah) and northwestern Mexico (Baja California del Norte, northwestern Sonora)|
|C. ravus||(Cope, 1865)||3||Mexican pygmy rattlesnake||The mountains of central and southern Mexico, west of the Isthmus of Tehuantepec, in the southeastern part of the Mexican Plateau, in the highlands of Morelos, Tlaxcala, Puebla, Veracruz, Oaxaca and the Sierra Madre del Sur in Guerrero.|
|C. ruber||Cope, 1892||3||Red diamond rattlesnake||The US in southwestern California, south through the Baja California Peninsula, except in the desert east of the Sierra de Juárez, also on a number of islands in the Gulf of California and three islands off the west coast of Baja California Sur|
|C. scutulatus||(Kennicott, 1861)||2||Mojave rattlesnake||The southwestern US in southern California, southern Nevada, extreme southwestern Utah, most of Arizona, southern New Mexico, and West Texas, and south into Mexico to southern Puebla|
|C. simus||Latreille In Sonnini & Latreille, 1801||0||Middle American rattlesnake||From Mexico in southwestern Michoacán on the Pacific coast, and Veracruz and the Yucatán Peninsula on the Atlantic coast, south through Belize, Guatemala, El Salvador, Honduras, and Nicaragua to west-central Costa Rica|
|C. stejnegeri||Dunn, 1919||0||Long-tailed rattlesnake||Western Mexico in eastern Sinaloa, western Durango, and probably northern Nayarit|
|C. stephensi||Klauber, 1930||0||Panamint rattlesnake||United States: eastern California, south-western Nevada|
|C. tancitarensis||Alvarado-Diaz & Campbell, 2004||0||Tancitaro rattlesnake||Mexico: Michoacán|
|C. thalassoporus||Meik, Schaack, FloreS-Villela, & Streicher, 2018||0||Louse Island speckled rattlesnake||Piojo Island, Baja California, Mexico|
|C. tigris||Kennicott in Baird, 1859||0||Tiger rattlesnake||The southwestern US in south-central Arizona, and in northwestern Mexico in Sonora, on Isla Tiburón in the Gulf of California|
|C. tlaloci||Bryson, Linkem, Dorcas, Lathrop, Jones, Alvarado-Diaz, Grünwald & Murphy, 2014||0||Mexico: Michoacan and Guerrero|
|C. totonacus||Gloyd & Kauffeld, 1940||0||Totonacan rattlesnake||Northeastern Mexico from central Nuevo León through southern Tamaulipas, northern Veracruz, eastern San Luis Potosí, and northern Querétaro.|
|C. transversus||Taylor, 1944||0||Cross-banded mountain rattlesnake||Central Mexico in the State of Mexico and Morelos.|
|C. triseriatus||(Wagler, 1830)||2||Mexican dusky rattlesnake||Mexico, along the southern edge of the Mexican Plateau in the highlands of the Transverse Volcanic Cordillera, including the states of Nayarit, Jalisco, Michoacán, Morelos, México, Puebla, Tlaxcala, and Veracruz|
|C. tzabcan||Klauber, 1952||0||Yucatán neotropical rattlesnake||Mexico (Yucatán, Campeche, Quintana Roo and eastern Tabasco), northern Guatemala and northern Belize|
|C. unicolor||Klauber, 1936||0||Aruba rattlesnake||Aruba|
|C. vegrandis||Klauber, 1941||0||Uracoan rattlesnake||Eastern Venezuela|
|C. viridis||(Rafinesque, 1818)||2||Prairie rattlesnake||Southern Canada (Alberta, Saskatchewan), south through the US (eastern Idaho, Montana, North Dakota, South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, Texas, New Mexico, extreme eastern Arizona), and into northern Mexico (northern Coahuila, northwestern Chihuahua)|
|C. willardi||Meek, 1905||5||Ridge-nosed rattlesnake||The US in southeastern Arizona and southwestern New Mexico, and northwestern Mexico in Sonora, Chihuahua, Durango, and Zacatecas|
- 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. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
- Wright AH, Wright AA (1957). Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock Publishing Associates (7th printing, 1985). 1,105 pp. (in 2 volumes). ISBN 0-8014-0463-0.
- Campbell JA, Lamar WW (2004). The Venomous Reptiles of the Western Hemisphere. Ithaca and London: Comstock Publishing Associates. 870 pp. 1,500 plates. ISBN 0-8014-4141-2.
- "Crotalus ". Integrated Taxonomic Information System. Retrieved 23 August 2007.
- "Crotalus ". The Reptile Database. www.reptile-database.org.
- Klauber LM (1997). Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind. Second Edition. (First published in 1956, 1972). Berkeley: University of California Press. ISBN 0-520-21056-5.
- Parker HW, Grandison AGC (1977). Snakes — a natural history. Second Edition. London and Ithaca: British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN 0-8014-1095-9 (cloth), ISBN 0-8014-9164-9 (paper).
- Stidworthy J (1974). Snakes of the World. New York: Grosset & Dunlap Inc. 160 pp. ISBN 0-448-11856-4.
- Canavero, Andrés; et al. (2010). "Conservation status assessment of the amphibians and reptiles of Uruguay". Iheringia. Série Zoologia. 100 (1): 05–12. doi:10.1590/s0073-47212010000100001.
- Duarte, Marcelo; Menezes, Frederico (2013). "Is the population of Crotalus durissus (Serpentes, Viperidae) expanding in Brazil?" (PDF). Journal of Venomous Animals and Toxins Including Tropical Diseases. 19 (1): 30. doi:10.1186/1678-9199-19-30. ISSN 1678-9199. PMC 4029606. PMID 24314146.
- Klauber, 1936, 1971, 1972.
- Keegan, 1944; Klauber, 1927, 1936, 1971, 1972.
- Klauber, 1936.
- Chang, Mei-Chi (1998). "Antithormbotic Effect of Crotalin, a Platelet Membrane Glycoprotein Ib Antagonist From Venom of Crotalus atrox". Blood. 91 (5): 1582–1589. doi:10.1182/blood.v91.5.1582.
- Hati, Rathanath (1999). "Snake Venom Hemorrhagins". Critical Reviews in Toxicology. 29 (1): 1–19. doi:10.1080/10408449991349168. PMID 10066158.
- Aird, SD; et al. (1985). "Rattlesnake presynaptic neurotoxins: primary structures and evolutionary origin of the acidic subunit". Biochemistry. 24 (25): 7054–7058. doi:10.1021/bi00346a005. PMID 4084559.
- Cope, ED (1867). "On the Reptilia and Batrachia of the Sonoran province of the Nearctic region". Proceedings of the Academy of Natural Sciences of Philadelphia. 18: 300–314 .
- Cope, ED (1883). "Notes on the geographical distribution of batrachia and reptilia in western North America". Proceedings of the Academy of Natural Sciences of Philadelphia. 35: 10–35 .
- Coues E (1875). "Synopsis of the Reptiles and Batrachians of Arizona; with Critical and Field Notes, and an Extensive Synonymy". pp. 585–633 . In: Wheeler GM (1875). Report Upon Geographical and Geological Explorations and Surveys West of the One Hundredth Meridian. Volume V. Zoology: Reports Upon the Zoological Collections Obtained from Portions of Nevada, Utah, California, Colorado, New Mexico, and Arizona, During the Years 1871, 1872, 1873, and 1874. Washington, District of Columbia: United States Government Printing Office.
- Fitzinger L (1843). Systema Reptilium. Fasciculus Primus. Amblyglossae. Vienna: Braumüller et Seidel. 106 pp. + indices . (in Latin).
- Gloyd HK (1940). "The Rattlesnakes, Genera Sistrurus and Crotalus. A Study in Zoogeography and Evolution". Special Publ. Chicago Acad. Sci. (4): 1-266, 10 figures, 31 plates.
- Heckel, JO; Sisson, DC; Quist, CF (1994). "Apparent fatal snakebite in three hawks". Journal of Wildlife Diseases. 30 (4): 616–619. doi:10.7589/0090-3558-30.4.616. PMID 7760504.
- Houttuyn, M (1764). Natuurlyke historie of uitvoerige beschryving der dieren, planten en mineraalen, volgens het samenstel van den Heer Linnæus. Met naauwkeurige afbeeldingen. Eerste deels, zesde stuk. Dieren van beiderley leven. Amsterdam. 558 pp. . (in Dutch).
- Hubbs, Brian; O'Connor, Brendan (2012). A Guide to the Rattlesnakes and other Venomous Serpents of the United States. Tempe, Arizona: Tricolor Books. 129 pp. ISBN 978-0-9754641-3-7.
- Keegan, HL (1944). "Indigo snakes feeding upon poisonous snakes". Copeia. 1944 (1): 59. doi:10.2307/1438255. JSTOR 1438255.
- Klauber, LM (1927). "Some observations on the rattlesnakes of the extreme southwest". Bull. Antivenin Inst. America. 1 (1): 7–21.
- Klauber, LM (1936). "Key to the rattlesnakes with summary characteristics". Trans. San Diego Soc. Nat. Hist. 8 (2): 185–276. doi:10.5962/bhl.part.14899.
- Klauber LM (1971). "Classification, distribution and biology of the venomous snakes of northern Mexico, the United States and Canada: Crotalus and Sistrurus ". pp. 115–156. In: Bucherl W, Buckley E (1971). Venomous animals and their venoms, vol. 2. Venomous vertebrates. New York: Academic Press.
- Klauber LM (1972). Rattlesnakes: Their habits, Life Histories, and Influence on Mankind. Second edition. 2 Volumes. Berkeley, California: University of California Press.
- Laurenti JN (1768). Specimen medicum, exhibens synopsin reptilium emendatum cum experimentis circa venena et antidota reptilium austriacorum. Vienna: Joan. Thom. Nob. de Trattern. 214 pp. + Plates I-V . (in Latin).
- Linnaeus C (1758). Systema naturae per regna tria naturae secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio Decima, Reformata [ Tenth Revised Edition, Volume 1]. Stockholm. 824 pp. . (in Latin).
- Powell R, Conant R, Collins JT (2016). Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition. Boston and New York: Houghton Mifflin Harcourt. xiv + 494 pp.  + Plates 1-47. ISBN 978-0-544-12997-9.
- Rafinesque CS (1815). Analyse de la nature ou tableau de l'univers et des corps organisés. Palermo: Jean Barravecchia. 224 pp. (Herpetology section) pp. 73–78 . (in French).
- Rafinesque CS (1820). "Annals of Nature, or Annual Synopsys of New Genera and Species of Animals and Plants Discovered in North America". Lexington (22): 1-16 .
- Reuss T (1930). "Glasnik Zemaljskog Muzeja u Bosni I Hercegovini ". Sveska za Prirodne Nauke 42: 57-114 [60, 88]. (in Bosnian).
- Schmidt KP, Davis DD (1941). Field Book of Snakes of the United States and Canada. New York: G.P. Putnam's Sons. 365 pp. [290-293].
- Wagler J (1830). Natürliches system der amphibien, mit vorangehender classification der Säugthiere und Vögel. Ein Beitrag zur vergleichenden Zoologie. Munich, Stuttgart and Tübingen: J.G. Cotta. vi + 354 pp. + one plate . (in German and Latin).