Crotalus

---

title: "Crotalus" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["crotalus", "snake-genera", "animal-taxa-named-by-carl-linnaeus"] description: "Genus of snakes" topic_path: "general/crotalus" source: "https://en.wikipedia.org/wiki/Crotalus" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Genus of snakes ::

| image = ZollmanTimberRattlesnake.jpg | image_caption = Crotalus horridus, the timber rattlesnake | image2 = Rattlesnake.ogg | image2_caption = Rattlesnake rattling | taxon = Crotalus | authority = Linnaeus, 1758 | synonyms = {{collapsible list|bullets = true|title=List |Crotalus Linnaeus, 1758 |Crotalophorus Houttuyn, 1764 |Caudisona Laurenti, 1768 |Crotalinus Rafinesque, 1815 |Crotalurus Rafinesque, 1820 |Crotulurus Rafinesque, 1820 |Uropsophus Wagler, 1830 |Urocrotalon Fitzinger, 1843 |Aploaspis Cope, 1867 |Aechmophrys Coues In Wheeler, 1875 |Haploaspis Cope, 1883 |Paracrotalus Reuss, 1930

Crotalus is a genus of pit vipers, commonly known as rattlesnakes or rattlers, in the family Viperidae. The genus is found only in the Americas from southern Canada to northern Argentina. 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. As of July 2023, 44 to 53 species are recognized as valid.

Description

Members of the genus Crotalus range in size from only 50–70 cm (C. intermedius, C. pricei), to over 150 cm (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. ::figure[src="https://upload.wikimedia.org/wikipedia/commons/c/cd/Rattle.jpg" caption="The rattle of a [[western diamondback rattlesnake]] (note the black and white colour at the base)"] ::

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, 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 the 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 several times in a year at a frequency that depends on their environment and how much they eat, every time adding a new segment to the rattle, the number of segments is a function of more than solely 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; nonetheless, finding specimens with as many as a dozen segments is not uncommon⁠and in captive specimens, as many as 29 segments have been documented.

Distribution and habitat

The genus Crotalus is found in the Americas from southern Canada to central Argentina.

Behavior

No species of Crotalus is considered aggressive; when threatened, most retreat quickly, but most species defend themselves readily when cornered.

There is no consensus in the available literature about how far rattlesnakes can strike, with estimates ranging from one-third to the entire body length of the rattlesnake. Strike distance depends not just on the snake's size, but also on many other factors, including its species, the position of its body, and its degree of agitation. This is compounded by a further lack of consensus as to the location on the anchor coil of the snake from where a strike should be measured. They rarely strike further than half of their body length, and almost never more than three-fourths, but trusting such values is unwise if only because it is not feasible to accurately judge the length of a coiled snake.

Feeding

The diets of species of Crotalus generally consist of vertebrates, although many invertebrate species are also 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 such as prairie dogs, tree squirrels, chipmunks, 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 to avoid their teeth, and these snakes evidently can discriminate between trails left by prey that has or has not been envenomated.

Predators

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 cats, 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.

Reproduction

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.

Several 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. In addition, species that occur further north, where weather 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.

Venom

Two main hemotoxic effects are caused by rattlesnake venom. First, zinc-containing metalloproteases act upon capillary endothelial cells to inhibit platelet aggregation and hemorrhage. Second, the platelet antagonist crotalin creates a severe bleeding effect as it binds to the surface proteins, blocking aggregation.

Neurotoxic effects may also be caused by rattlesnake venom. These effects vary by species, and within species by population.

Species

::data[format=table]

Image	Species	Taxon author	Subsp.*	Common name	Geographic range
[[File:Crotalus adamanteus 25.jpg	190px]]	C. adamanteus	Palisot de Beauvois, 1799	0	Eastern diamondback rattlesnake
	C. angelensis	Klauber, 1963	0	Angel de la Guarda Island speckled rattlesnake	Isla Ángel de la Guarda in the Gulf of California, Mexico
[[File:Crotalus aquilus.jpg	190px]]	C. aquilus	Klauber, 1952	0	Querétaro dusky rattlesnake
[[File:Crotalus armstrongi in Morelia zoo.jpg	251x251px]]	C. armstrongi	Campbell, 1979	0	Western dusky rattlesnake
[[File:Crotalus atrox USFWS.jpg	190px]]	C. atrox	Baird & Girard, 1853	0	Western diamondback rattlesnake
[[File:Crotalus basiliscus.jpg	190px]]	C. basiliscus	(Cope, 1864)	0	Mexican west coast rattlesnake
	C. campbelli	Bryson, Linkem, Dorcas, Lathrop, Jones, Alvarado-Diaz, Grünwald & Murphy, 2014	0	Campbell's rattlesnake	Mexico: western Jalisco, northwestern Colima
[[File:Gfp-santa-cataline-island-rattlesnake.jpg	190px]]	C. catalinensis	Cliff, 1954	0	Santa Catalina rattlesnake
[[File:Crotalus cerastes mesquite springs CA-2.jpg	190px]]	C. cerastes	Hallowell, 1854	3	Sidewinder,
[[File:Arizona Black Rattlesnake.jpg	190px]]	C. cerberus	(Coues, 1875)	0	Arizona black rattlesnake
[[File:Crotalus oreganus concolor 01.jpg	190px]]	C. concolor	(Woodbury, 1929)	0	Midget faded rattlesnake
[[File:Gfp-northwestern-neotropical-rattlesnake.jpg	190px]]	C. culminatus	Klauber, 1952	0	Northwestern neotropical rattlesnake
[[File:Cascabelle.JPG	190px]]	C. durissus	Linnaeus, 1758	7	South American rattlesnake
	C. ehecatl	Carbajal-Marquez, Cedeno-Vazquez, Martinez-Arce, Neri-Castro, & Machkour-M'rabet, 2020	0	Tehuantepec Isthmus Neotropical rattlesnake	Mexico: (Chiapas, Oaxaca)
[[File:Crotalus enyo.JPG	190px]]	C. enyo	(Cope, 1861)	2	Baja California rattlesnake
	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)
[[File:Crotalus viridis helleri.jpg	190px]]	C. helleri	(Meek, 1905)	0	Southern Pacific rattlesnake
[[File:ZollmanTimberRattlesnake.jpg	190px]]	*C. horridus*T	Linnaeus, 1758	0	Timber rattlesnake
[[File:Mexican Smallhead Rattlesnake imported from iNaturalist photo 46759429 on 5 February 2022.png	190px]]	C. intermedius	Troschel, 1865	2	Mexican small-headed rattlesnake
	C. lannomi	W. Tanner, 1966	0	Autlán rattlesnake	Western Mexico in Jalisco
[[File:Crotalus lepidus lepidus 1.jpg	190px]]	C. lepidus	(Kennicott, 1861)	2	Rock rattlesnake
	C. lorenzoensis	Radcliffe & Maslin, 1975	0	San Lorenzo Island red diamond rattlesnake	Mexico, San Lorenzo Island in the Gulf of California
[[File:Rattlesnake (Marshal Hedin).jpg	190px]]	C. lutosus	(Klauber, 1930)	0	Great Basin rattlesnake
	C. mictlantecuhtli	Carbajal-Marquez, Cedeno-Vazquez, Martinez-Arce, Neri-Castro, & Machkour-M'rabet, 2020	0	Veracruz Neotropical rattlesnake	Mexico: (Veracruz)
[[File:Speckled Rattlesnake (Crotalus mitchellii) (21705787199).jpg	190px]]	C. mitchellii	(Cope, 1861)	1	Speckled rattlesnake
[[File:Northern black-tailed rattlesnake.jpg	190px]]	C. molossus	Baird & Girard, 1853	3	Black-tailed rattlesnake
[[File:Crotalus morulus, Tamaulipan Rock Rattlesnake, Tamailipas.jpg	190px]]	C. morulus	Klauber, 1952	0	Tamaulipan rock rattlesnake
[[File:Crotalus oreganus.jpg	190px]]	C. oreganus	Holbrook, 1840	0	Western rattlesnake
[[File:Crotalus ornatus 158434960.jpg	190px]]	C. ornatus	Hallowell, 1854	0	Eastern black-tailed rattlesnake
	C. polisi	Meik, Schaack, FloreS-Villela, & Streicher, 2018	0	Horsehead Island speckled rattlesnake	Cabeza de Caballo Island, Baja California, Mexico
[[File:Crotalus Polystictus.jpg	190px]]	C. polystictus	(Cope, 1865)	0	Mexican lance-headed rattlesnake
[[File:Crotalus pricei.jpg	190px]]	C. pricei	Van Denburgh, 1895	1	Twin-spotted rattlesnake
[[File:Crotalus pusillus 72647737.jpg	190px]]	C. pusillus	Klauber, 1952	0	Tancitaran dusky rattlesnake
[[File:Crotalus-mitchellii.jpg	190px]]	C. pyrrhus	Cope, 1867	0	Southwestern speckled rattlesnake
[[File:Crotalus ravus cropped2.jpg	190px]]	C. ravus	(Cope, 1865)	3	Mexican pygmy rattlesnake
[[File:Crotalus ruber 02.jpg	190px]]	C. ruber	Cope, 1892	2	Red diamond rattlesnake
[[File:Crotalus scutulatus 02.JPG	190px]]	C. scutulatus	(Kennicott, 1861)	1	Mojave rattlesnake
[[File:Yucatan Neotropical Rattlesnake 045.jpg	190px]]	C. simus	Latreille In Sonnini & Latreille, 1801	0	Middle American rattlesnake
	C. stejnegeri	Dunn, 1919	0	Long-tailed rattlesnake	Western Mexico in eastern Sinaloa, western Durango, and probably northern Nayarit
[[File:Crotalus stephensi.JPG	190px]]	C. stephensi	Klauber, 1930	0	Panamint rattlesnake
	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
[[File:Tiger Rattlesnake 001.jpg	190px]]	C. tigris	Kennicott in Baird, 1859	0	Tiger rattlesnake
	C. tlaloci	Bryson, Linkem, Dorcas, Lathrop, Jones, Alvarado-Diaz, Grünwald & Murphy, 2014	0		Mexico: Michoacan and Guerrero
[[File:Crotalus totonacus, Totonacan Rattlesnake, Tamaulipas.jpg	190px]]	C. totonacus	Gloyd & Kauffeld, 1940	0	Totonacan rattlesnake
[[File:Gfp-cross-banded-rattlesnake.jpg	190px]]	C. transversus	Taylor, 1944	0	Cross-banded mountain rattlesnake
[[File:Crotalus triseriatus in Morelia zoo.jpg	190px]]	C. triseriatus	(Wagler, 1830)	1	Mexican dusky rattlesnake
[[File:Crotalus-simus-tzabcan.jpg	190px]]	C. tzabcan	Klauber, 1952	0	Yucatán neotropical rattlesnake
[[File:Crotalus unicolor.jpg	190px]]	C. unicolor	Klauber, 1936	0	Aruba rattlesnake
[[File:Crotale venezuela 19.JPG	190px]]	C. vegrandis	Klauber, 1941	0	Uracoan rattlesnake
[[File:Crotalus viridis 02.jpg	190px]]	C. viridis	(Rafinesque, 1818)	3	Prairie rattlesnake
[[File:Arizona ridgenosed rattlesnake closeup.jpg	190px]]	C. willardi	Meek, 1905	5	Ridge-nosed rattlesnake
::

***) Not including the nominate subspecies

T) Type species

References

References

1. [[:fr:Roy Wallace McDiarmid. McDiarmid RW]], [[Jonathan A. Campbell. Campbell JA]], [[species:T'Shaka A. Touré. Touré TA]] (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).
2. [[Albert Hazen Wright. Wright AH]], [[species:Anna Allen Wright. 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.
3. [[Jonathan A. Campbell. Campbell JA]], [[species:William W. Lamar. 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.
4. {{ITIS
5. {{EMBL genus
6. [[Laurence Monroe Klauber. 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.
7. [[Hampton Wildman Parker. Parker HW]], [[species:Alice Georgie Cruicksnank Grandison. 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).
8. [[species:John Stidworthy. Stidworthy J]] (1974). ''Snakes of the World''. New York: Grosset & Dunlap Inc. 160 pp. {{ISBN. 0-448-11856-4.
9. (2010). "Conservation status assessment of the amphibians and reptiles of Uruguay". Iheringia. Série Zoologia.
10. (2013). "Is the population of ''Crotalus durissus'' (Serpentes, Viperidae) expanding in Brazil?". Journal of Venomous Animals and Toxins Including Tropical Diseases.
11. Klauber, 1936, 1971, 1972.
12. Keegan, 1944; Klauber, 1927, 1936, 1971, 1972.
13. Klauber, 1936.
14. (1998). "Antithormbotic Effect of Crotalin, a Platelet Membrane Glycoprotein Ib Antagonist From Venom of ''Crotalus atrox''". Blood.
15. (1999). "Snake Venom Hemorrhagins". Critical Reviews in Toxicology.
16. (1985). "Rattlesnake presynaptic neurotoxins: primary structures and evolutionary origin of the acidic subunit". Biochemistry.
17. (2018-03-23). "Phenotypic Variation in Mojave Rattlesnake (Crotalus scutulatus) Venom Is Driven by Four Toxin Families". Toxins.
18. (2019-03-13). "When one phenotype is not enough: divergent evolutionary trajectories govern venom variation in a widespread rattlesnake species". Proceedings of the Royal Society B: Biological Sciences.
19. (2021-11-05). "Varying Intensities of Introgression Obscure Incipient Venom-Associated Speciation in the Timber Rattlesnake (Crotalus horridus)". Toxins.
20. [[species:Manuel Acevedo. Acevedo M]], [[species:Jerry D. Johnson. Johnson J]], [[species:Daniel Ariano-Sánchez. Ariano-Sánchez D]] (2014). "''Crotalus tzabcan'' ". The [[IUCN]] Red List of Threatened Species 2014: e.T197478A2488339. https://dx.doi.org/10.2305/IUCN.UK.2014-1.RLTS.T197478A2488339.en. Downloaded on 30 April 2021.

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::