Common names: rattlesnake

Rattlesnake

Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae . There are 32 known species of rattlesnake, with between 65-70 subspecies, all native to the Americas, ranging from southern Alberta and southern British Columbia in Canada to Central...

s, rattlers.

Crotalus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of venomous

Venomous snake

"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...

 pit vipers found only in the Americas

Americas

The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

 from southern Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 to northern Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

. The name is derived from the Greek word krotalon, which means "rattle" or "castanet", and refers to the rattle on the end of the tail which makes this group (genera Crotalus and Sistrurus

Sistrurus

Sistrurus is a genus of venomous pit vipers found in Canada, the United States and Mexico. The name is a Latinized form of the Greek word for "tail rattler" and shares its root with the ancient Egyptian musical instrument, the sistrum, a type of rattle...

) so distinctive. 29 species are currently recognized.

Description

Members of this genus range in size from only 50-60 cm (C. intermedius

Crotalus intermedius

Crotalus intermedius is a venomous pitviper species found in central and southern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.-Description:...

, C. pricei

Crotalus pricei

Crotalus pricei is a venomous pitviper species found in the United States and Mexico. Currently, two subspecies are recognized, including the nominate subspecies described here.-Description:Adults usually do not exceed 50–60 cm in length...

), to over 150 cm (C. adamanteus

Crotalus adamanteus

Crotalus adamanteus is a venomous pit viper species found in the southeastern United States. It is the heaviest venomous snake in the Americas and the largest rattlesnake. It featured prominently in the American Revolution, specifically as the symbol of what many consider to be the first flag of...

, C. atrox

Crotalus atrox

Crotalus atrox, the "western diamondback rattlesnake", is a venomous rattlesnake species found in the United States and Mexico. It is likely responsible for the majority of snakebite fatalities in northern Mexico and the second greatest number in the USA after C. adamanteus. No subspecies are...

). 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 the tail, although a few island populations form exceptions to this rule: C. catalinensis

Crotalus catalinensis

Crotalus catalinensis is a venomous pitviper endemic to Isla Santa Catalina located in the Gulf of California just off the eastern coast of the state of Baja California Sur, Mexico. No subspecies are currently recognized...

 has lost its rattle entirely, C. ruber lorenzoensis

Crotalus ruber lorenzoensis

Crotalus ruber lorenzoensis is a venomous pitviper subspecies endemic to San Lorenzo Sur Island, Mexico.-Description:This subspecies usually has no rattle, and has shranked in size compared to some of its other subspecies counterparts on the mainland....

 usually has no rattle, and both C. r. lucasensis

Crotalus ruber lucasensis

Crotalus ruber lucasensis is a venomous pitviper subspecies found in Mexico in the cape region of lower Baja California.-Description:Similarly to C. r. ruber, adult specimens commonly exceed 100 cm in length...

 and C. molossus estebanensis

Crotalus molossus estebanensis

Crotalus molossus estebanensis is a venomous pitviper subspecies endemic to San Estéban Island, Mexico.-Geographic range:Known only from the type locality, which is "San Estéban Island, Gulf of California, Mexico.-Conservation status:...

 exhibit a tendency for rattle loss. The rattle may also be lacking in any species due to a congenital abnormality.

The rattle itself 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 that prevent it from falling off. Before each molt, a new button will have developed inside the last one and before the skin is shed, the tip of new button shrinks, thereby loosening the shell of the previous one. This process continues so that a succession of molts produces an appendage that consists of a number of interlocking segments that make an audible noise when vibrated. Since younger specimens may shed 3-4 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 6-7 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.

Behavior

None are considered aggressive. In fact, when threatened most will retreat quickly. However, most species will defend themselves readily when cornered.

A highly controversial issue has always been how far these snakes can strike. Obviously this depends on the size of the animal, but other factors may also play a role, such as the species, the position the body is in and the degree of excitement. Additionally, there is the question of definition: 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 ⅓ of the body length, to ½, to ⅔, and even the full length of the animal. Klauber (1997) considered that they rarely strike further than ½ of their body length, and almost never more than ¾, but that 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.

Feeding

The diet generally consists of vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, although many invertebrate

Invertebrate

An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 species have also been noted. 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. According to Klauber (1936, 1971, 1972), prey items more frequently taken include rabbits, ground squirrels, tree squirrels, chipmunks, prairie dogs, gophers, 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 will usually release their prey after a strike and there is evidence that these snakes can discriminate between trails left by prey that has and has not been envenomated.

Predators

For all species, the most significant threats come from people, but they also face many natural enemies. These include other snakes, such as kingsnakes (Lampropeltis), coachwhips (Masticophis

Masticophis

Masticophis is a genus of colubrid snakes that are commonly referred to as whip snakes or coachwhips. They are characterized by having a long, thin body and are not dangerous.- Species :...

), indigo snakes (Drymarchon

Drymarchon

Indigo snakes are a genus of large non-venomous colubrid snakes found in Southeastern United States, Central America, and South America. Three to four species are currently recognized.-Description:...

) and racers (Coluber

Coluber

Coluber is a genus of thin bodied, fast moving, colubrid snakes commonly known as racers. They are widespread around the world and vary greatly in habitat and behaviour. In the past, Coluber was a catch-all genus which included almost all snake species known at the time...

); birds, such as hawks, eagles, owls, roadrunners and ravens; and mammals, such as coyotes, foxes, wildcats, badgers, skunks and pigs (Keegan, 1944; Klauber, 1927, 1936, 1971, 1972). Certain species of birds frequently prey on these snakes, but this is not without risk. Heckel et al. (1994) described two cases in which dead hawks were found near venomous snakes and had suffered hemorrhage and gangrenous necrosis. Their conclusion was that this was due to snakebite.

Reproduction

This genus is ovoviviparous, giving birth to live young. The basic life cycle of many Nearctic species has been known for quite some time. Klauber (1936) describes how females at an age of 26 months undergo vitellogenesis

Vitellogenesis

Vitellogenesis is the process of yolk formation via nutrients being deposited in the oocyte, or female germ cell involved in reproduction. It starts when the fat body stimulates the release of juvenile hormones and produces vitellogenin protein. It occurs in all animal groups lower than the mammals...

 as they enter their third hibernation

Hibernation

Hibernation is a state of inactivity and metabolic depression in animals, characterized by lower body temperature, slower breathing, and lower metabolic rate. Hibernating animals conserve food, especially during winter when food supplies are limited, tapping energy reserves, body fat, at a slow rate...

, mate the following spring and give birth a number of months later in September or October.

There are, however, a number of variations to this basic cycle. In North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, this is due to the ability of the females of some species to store sperm in the oviduct for at least eight months, and the males (all species of which undergo spermatogenesis

Spermatogenesis

Spermatogenesis is the process by which male primary germ cells undergo division, and produce a number of cells termed spermatogonia, from which the primary spermatocytes are derived. Each primary spermatocyte divides into two secondary spermatocytes, and each secondary spermatocyte into two...

 during the summer) to store sperm in the vas deferens

Vas deferens

The vas deferens , also called ductus deferens, , is part of the male anatomy of many vertebrates; they transport sperm from the epididymis in anticipation of ejaculation....

 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 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 that are found in central and southern Mexico or the tropics have reproductive cycles that correspond mostly with the rainy season.

Venom

There are two main hemotoxic

Hemotoxin

Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells , disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term hemotoxin is to some degree a misnomer since toxins that damage the blood also damage other tissues...

 effects caused by rattlesnake venom. First are the zinc-containing metalloproteases that act upon capillary endothelial cells. This effect can cause platelet aggregation and hemorrhage. Second is the platelet antagonist crotalin; this toxin creates a severe bleeding effect as it binds to the surface proteins blocking aggregation. These two starkly different effects may seem counter productive, however the effect should be profound. Firstly if the endothelial cells are disrupted this will cause a lysis effect and internal bleeding. Then as these hemorrhages increase, the natural thrombin response is hindered by the effect of crotalin increasing the toxic effect. Observed hunting technique is a bite and release method; so a fast acting toxin would be ideal. Assuming that 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 spreading the hemolytic and hemorrhagic effect.

Neurotoxic

Neurotoxin

A neurotoxin is a toxin that acts specifically on nerve cells , usually by interacting with membrane proteins such as ion channels. Some sources are more general, and define the effect of neurotoxins as occurring at nerve tissue...

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

Species

Species	Taxon author	Subsp.*	Common name	Geographic range
C. adamanteus Crotalus adamanteus Crotalus adamanteus is a venomous pit viper species found in the southeastern United States. It is the heaviest venomous snake in the Americas and the largest rattlesnake. It featured prominently in the American Revolution, specifically as the symbol of what many consider to be the first flag of...	Palisot de Beauvois Palisot de Beauvois Ambroise Marie François Joseph Palisot, Baron de Beauvois 27 July 1752 Arras - 21 January 1820 Paris, was a French naturalist.Palisot collected insects in Oware, Benin, Saint Domingue, and the United States, during the period 1786 – 1797. Trained as a botanist, Palisot published a significant... , 1799	0	Eastern diamondback rattlesnake	The southeastern United States United States The United States of America is a federal constitutional republic comprising fifty states and a federal district...  from southeastern North Carolina North Carolina North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte... , south along the coastal plain through peninsular Florida Florida Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...  to the Florida Keys Florida Keys The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry... , and west along the Gulf Coast though southern Mississippi Mississippi Mississippi is a U.S. state located in the Southern United States. Jackson is the state capital and largest city. The name of the state derives from the Mississippi River, which flows along its western boundary, whose name comes from the Ojibwe word misi-ziibi...  to southeastern Louisiana Louisiana Louisiana is a state located in the southern region of the United States of America. Its capital is Baton Rouge and largest city is New Orleans. Louisiana is the only state in the U.S. with political subdivisions termed parishes, which are local governments equivalent to counties... .
C. aquilus Crotalus aquilus Crotalus aquilus is a venomous pitviper species found in the highlands of central Mexico. No subspecies are currently recognized. The specific name, aquilus, is Latin for "eagle" and refers to the high altitude at which this species is found....	Klauber Laurence Monroe Klauber Laurence M. Klauber , was an American herpetologist, and was considered to be the foremost authority on rattlesnakes... , 1952	0	Querétaro dusky rattlesnake	The highlands of central Mexico Mexico The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of... : Guanajuato Guanajuato Guanajuato officially Estado Libre y Soberano de Guanajuato is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 46 municipalities and its capital city is Guanajuato.... , Hidalgo, México Mexico (state) México , officially: Estado Libre y Soberano de México is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of the United Mexican States. It is divided in 125 municipalities and its capital city is Toluca de Lerdo.... , Michoacán Michoacán Michoacán officially Estado Libre y Soberano de Michoacán de Ocampo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 113 municipalities and its capital city is Morelia...  and San Luis Potosí San Luis Potosí San Luis Potosí officially Estado Libre y Soberano de San Luis Potosí is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 58 municipalities and its capital city is San Luis Potosí.... .
C. atrox Crotalus atrox Crotalus atrox, the "western diamondback rattlesnake", is a venomous rattlesnake species found in the United States and Mexico. It is likely responsible for the majority of snakebite fatalities in northern Mexico and the second greatest number in the USA after C. adamanteus. No subspecies are...	Baird Spencer Fullerton Baird Spencer Fullerton Baird was an American ornithologist, ichthyologist and herpetologist. Starting in 1850 he was assistant-secretary and later secretary of the Smithsonian Institution in Washington, D.C...  & Girard Charles Frédéric Girard Charles Frédéric Girard was a French biologist specializing in ichthyology and herpetology.Born in Mulhouse, France, he studied at the College of Neuchâtel, Switzerland as a student of Louis Agassiz. In 1847, he accompanied Agassiz as his assistant to Harvard... , 1853	0	Western diamondback rattlesnake	The United States from central Arkansas Arkansas Arkansas is a state located in the southern region of the United States. Its name is an Algonquian name of the Quapaw Indians. Arkansas shares borders with six states , and its eastern border is largely defined by the Mississippi River...  and southeastern California California California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area... , south into Mexico as far as northern Sinaloa Sinaloa Sinaloa officially Estado Libre y Soberano de Sinaloa is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 18 municipalities and its capital city is Culiacán Rosales.... , Hidalgo and northern Veracruz Veracruz Veracruz, formally Veracruz de Ignacio de la Llave officially Estado Libre y Soberano de Veracruz de Ignacio de la Llave , is one of the 31 states that, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided in 212 municipalities and its capital city is... . Disjunct populations exist is southern Veracruz and southeastern Oaxaca Oaxaca Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions... .
C. basiliscus Crotalus basiliscus Crotalus basiliscus is a venomous pitviper species found in western Mexico. The specific name is derived from the Greek word for king, basiliskos, and is an allusion to this snake's large size and potent venom. No subspecies are currently recognized....	(Cope Edward Drinker Cope Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen... , 1864)	0	Mexican west coast rattlesnake	Western Mexico from southern Sonora Sonora Sonora officially Estado Libre y Soberano de Sonora is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided into 72 municipalities; the capital city is Hermosillo....  to Michoacán.
C. catalinensis Crotalus catalinensis Crotalus catalinensis is a venomous pitviper endemic to Isla Santa Catalina located in the Gulf of California just off the eastern coast of the state of Baja California Sur, Mexico. No subspecies are currently recognized...	Cliff, 1954	0	Santa Catalina rattlesnake	Isla Santa Catalina in the Gulf of California Gulf of California The Gulf of California is a body of water that separates the Baja California Peninsula from the Mexican mainland...  (western Mexico).
C. cerastes Crotalus cerastes Crotalus cerastes is a venomous pitviper species found in the desert regions of the southwestern United States and northwestern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.-Description:...	Hallowell, 1854	2	Sidewinder	The southwestern United States in the desert region of eastern California, southern Nevada Nevada Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its... , extreme southwestern Utah Utah Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...  and western Arizona Arizona Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix... . In northwestern Mexico in western Sonora and eastern Baja California Baja California Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North... .
C. durissus Crotalus durissus Crotalus durissus is a venomous pitviper species found in South America. The most widely distributed member of its genus, this species poses a serious medical problem in many parts of its range...	Linnaeus Carolus Linnaeus Carl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology... , 1758	8	South American rattlesnake	Found in all South America South America South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east... n countries except Chile Chile Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...  and Ecuador Ecuador Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border... , although the various populations are disjunct. Also occurs on some islands in the Caribbean Caribbean The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north... .
C. enyo Crotalus enyo Crotalus enyo is a venomous pitviper species native to the coast and islands of northwestern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.-Description:...	(Cope, 1861)	2	Baja California rattlesnake	Western Mexico on the Baja California Peninsula Baja California Peninsula The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...  from around Río San Telmo on the west coast and from opposite Isla Angel de la Guarda Isla Ángel de la Guarda Isla Ángel de la Guarda, also called Archangel Island, and called Xazl Iimt east of Bahía de los Ángeles, and separated from the Baja California Peninsula by the Canal de Ballenas . It is the second largest of the eleven Midriff Islands or Islas Grandes. It is part of the state of Baja California,...  on the gulf coast, south to Cabo San Lucas Cabo San Lucas Cabo San Lucas , commonly called Cabo, is a city at the southern tip of the Baja California peninsula, in the municipality of Los Cabos in the Mexican state of Baja California Sur. As of the 2010 census, the population was 68,463 people... . Also 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 it is also found on the island of San Margarita.
C. horridus Crotalus horridus Crotalus horridus, the timber rattlesnake, is a species of venomous pitviper found in the eastern United States. This is the only rattlesnake species in most of the populous northeastern United States. No subspecies are currently recognized.... T	Linnaeus, 1758	0	Timber rattlesnake	The eastern United States from southern Minnesota Minnesota Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...  and southern Maine Maine Maine is a state in the New England region of the northeastern United States, bordered by the Atlantic Ocean to the east and south, New Hampshire to the west, and the Canadian provinces of Quebec to the northwest and New Brunswick to the northeast. Maine is both the northernmost and easternmost... , south to east Texas Texas Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...  and north Florida. Also in southern Canada Canada Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...  in southern Ontario Ontario Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa.... .
C. intermedius Crotalus intermedius Crotalus intermedius is a venomous pitviper species found in central and southern Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.-Description:...	Troschel Franz Hermann Troschel Franz Hermann Troschel was a German zoologist who was born in Spandau. He studied mathematics and natural history at the University of Berlin, and beginning in 1840 was an assistant to Martin Lichtenstein at the Humboldt Museum of Natural History in Berlin... , 1865	2	Mexican small-headed rattlesnake	Central and southern Mexico, in southeastern Hidalgo, southern Tlaxcala Tlaxcala Tlaxcala officially Estado Libre y Soberano de Tlaxcala is one of the 31 states which along with the Federal District comprise the 32 federative entities of Mexico. It is divided into 60 municipalities and its capital city is Tlaxcala.... , northeastern and south-central Puebla Puebla Puebla officially Estado Libre y Soberano de Puebla is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 217 municipalities and its capital city is Puebla.... , west-central Veracruz, Oaxaca and Guerrero Guerrero Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo.... .
C. lannomi Crotalus lannomi Crotalus lannomi is a venomous pitviper species found in Mexico in Jalisco. Known from only a single specimen. No subspecies are currently recognized.-Description:...	Tanner, 1966	0	Autlán rattlesnake	Western Mexico in Jalisco Jalisco Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states... .
C. lepidus Crotalus lepidus Crotalus lepidus is a venomous pitviper species found in the southwestern United States and northern central Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.-Description:...	(Kennicott Robert Kennicott Robert Kennicott was an American naturalist.-Biography:Kennicott was born in New Orleans and grew up in "West Northfield" , Illinois, a town in the prairie north of the then nascent city of Chicago.... , 1861)	3	Rock rattlesnake	The southwestern United States in Arizona, southern New Mexico New Mexico New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...  and southwestern Texas, south into northern central Mexico.
C. mitchellii Crotalus mitchellii Crotalus mitchellii is a venomous pitviper species found in the Southwestern United States, and in northern Mexico. It was named in honor of Silas Weir Mitchell , a medical doctor who also studied rattlesnake venoms...	(Cope, 1861)	4	Speckled rattlesnake	The southwestern United States in east-central and southern California, southwestern Nevada, extreme southwestern Utah and western Arizona. In Mexico in most of Baja California, including Baja California Sur Baja California Sur Baja California Sur , is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. Before becoming a state on October 8, 1974, the area was known as the South Territory of Baja California. It has an area of , or 3.57% of the land mass of Mexico and comprises... . Also found on a number of islands in the Gulf of California and on Santa Margarita Island off the Pacific coast of Baja California Sur.
C. molossus Crotalus molossus Crotalus molossus is a venomous pitviper species found in the southwestern United States and Mexico. Four subspecies are currently recognized, including the nominate subspecies described here.-Description:...	Baird & Girard, 1853	3	Black-tailed rattlesnake	The southwestern United States in Arizona, New Mexico and west and central Texas. In Mexico as far south as Oaxaca. Also found in the Gulf of California on San Estéban Island and Tiburón Island Tiburón Island Tiburón Island is both the largest island in the Gulf of California and the largest island in Mexico, with an area of . It was made a nature reserve in 1963 by President Adolfo López Mateos. Tiburón is Spanish for shark. The etymology of the Seri name is unknown... .
C. oreganus Crotalus oreganus Crotalus oreganus is a venomous pitviper species found in North America in the western United States, parts of British Columbia and northwestern Mexico. Seven subspecies are currently recognized, including the nominate subspecies described here....	Holbrook John Edwards Holbrook John Edwards Holbrook American zoologist, herpetologist, physician, and naturalist, was born in Beaufort, South Carolina, the son of Silas Holbrook, a teacher, and Mary Edwards.... , 1840	6	Western rattlesnake	Southwestern Canada (southern British Columbia British Columbia British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858... ), south though much of the western half of the United States United States The United States of America is a federal constitutional republic comprising fifty states and a federal district...  (Washington, Oregon Oregon Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern... , western and southern Idaho Idaho Idaho is a state in the Rocky Mountain area of the United States. The state's largest city and capital is Boise. Residents are called "Idahoans". Idaho was admitted to the Union on July 3, 1890, as the 43rd state.... , California, Nevada, Utah, Arizona, and likely west-central New Mexico), and into northern Mexico (western Baja California (state) Baja California Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...  and the extreme north of Baja California Sur).
C. polystictus Crotalus polystictus Crotalus polystictus is a venomous pitviper species found in central Mexico. No subspecies are currently recognized.-Description:Adults usually grow to 60-70 cm, although exceptionally large specimens may be as much as 100 cm in length....	(Cope, 1865)	0	Mexican lance-headed rattlesnake	Central Mexican Plateau, from southern Zacatecas Zacatecas Zacatecas officially Estado Libre y Soberano de Zacatecas is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 58 municipalities and its capital city is Zacatecas....  and northeastern Colima Colima Colima is one of the 31 states which, with the Federal District, make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima....  east to east-central Veracruz.
C. pricei Crotalus pricei Crotalus pricei is a venomous pitviper species found in the United States and Mexico. Currently, two subspecies are recognized, including the nominate subspecies described here.-Description:Adults usually do not exceed 50–60 cm in length...	Van Denburgh John Van Denburgh John Van Denburgh was a U.S. herpetologist from California.He was born in San Francisco and enrolled at Stanford University in 1891. As of 1895, he organized the herpetology department of the California Academy of Sciences. In 1897 he got a Ph.D. from Stanford University. Additionally, he got an M.D... , 1895	1	Twin-spotted rattlesnake	In the United States from southeastern Arizona and Mexico in northern Sonora southeast through Chihuahua, Durango, southeastern Cohuila and Nuevo León into Tamaulipas.
C. pusillus Crotalus pusillus Crotalus pusillus is a venomous pitviper species found in west-central Mexico. No subspecies are currently recognized.-Description:Adult males may grow to more than 50 cm in length. Females are smaller. The largest recorded length for a specimen is 68.2 cm.-Behavior:Campbell and Lamar stated that...	Klauber, 1952	0	Tancitaran dusky rattlesnake	West-central Mexico in southwestern and west-central Michoacán and adjacent Jalisco. Probably also in northeastern Colima.
C. ruber Crotalus ruber Crotalus ruber is a venomous pitviper species found in southwestern California in the United States and Baja California in Mexico. Three subspecies are currently recognized, including the nominate subspecies described here.-Description:...	Cope, 1892	2	Red diamond rattlesnake	The United States in southwestern California, south through the Baja California Peninsula, except in the desert east of the Sierra de Juárez Sierra de Juárez Sierra de Juárez is a mountain range on the Baja California Peninsula, of Baja California, Mexico. It is part of the Peninsular Ranges. The Laguna Mountains of California lie to the north and the Sierra San Pedro Mártir lies to the south.... . Also found on a number of islands in the Gulf of California and two islands off the west coast of Baja California Sur.
C. scutulatus Crotalus scutulatus Crotalus scutulatus is a venomous pitviper species found in the deserts of the southwestern United States and central Mexico. It is perhaps best known for its potent neurotoxic venom...	(Kennicott, 1861)	1	Mohave rattlesnake	The southwestern United States in southern California, southern Nevada, extreme southwestern Utah, most of Arizona, southern New Mexico and western Texas, and south into Mexico to southern Puebla.
C. simus Crotalus simus Crotalus simus is a venomous pitviper species found in Mexico and Central America. The specific epithet is Latin for "flat nosed"; likely an allusion to the fact that its head is relatively blunt when compared with the lanceheads...	Latreille Pierre André Latreille Pierre André Latreille was a French zoologist, specialising in arthropods. Having trained as a Roman Catholic priest before the French Revolution, Latreille was imprisoned, and only regained his freedom after recognising a rare species he found in the prison, Necrobia ruficollis...  In Sonnini Charles-Nicolas-Sigisbert Sonnini de Manoncourt Charles-Nicolas-Sigisbert Sonnini de Manoncourt was a French naturalist. Between 1799 to 1808 he wrote 127 volumes of the Histoire naturelle. Noteworthy among these, especially for herpetologists, is Histoire naturelle des Reptiles, avec figures desinées d'après nature, in four volumes, which he...  & Latreille, 1801	2	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 Costa Rica Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east.... .
C. stejnegeri Crotalus stejnegeri Crotalus stejnegeri is a venomous pitviper species found in western Mexico. No subspecies are currently recognized.-Description:Adults do not usually grow to more than 60 cm in length. The greatest length recorded for a specimen is 72.4 cm. The tail is relatively long, representing 11-14.8% of the...	Dunn, 1919	0	Long-tailed rattlesnake	Western Mexico in eastern Sinaloa, western Durango and probably northern Nayarit Nayarit Nayarit officially Estado Libre y Soberano de Nayarit is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 20 municipalities and its capital city is Tepic.It is located in Western Mexico... .
C. tigris Crotalus tigris Crotalus tigris is a venomous pit viper species found in the southwestern United States and northwestern Mexico. No subspecies are currently recognized. The specific name is Latin for tiger and is an allusion to many narrow dorsal crossbands that create a pattern of vertical stripes.-Description: A...	Kennicott In Baird, 1859	0	Tiger rattlesnake	The southwestern United States in south-central Arizona, and in northwestern Mexico in Sonora. Also found on Isla Tiburón Tiburón Island Tiburón Island is both the largest island in the Gulf of California and the largest island in Mexico, with an area of . It was made a nature reserve in 1963 by President Adolfo López Mateos. Tiburón is Spanish for shark. The etymology of the Seri name is unknown...  in the Gulf of California.
C. tortugensis Crotalus tortugensis Crotalus tortugensis is a venomous pitviper species found only on Tortuga Island in the Gulf of California. No subspecies are currently recognized.-Description:...	Van Denburgh & Slevin, 1921	0	Tortuga island diamond rattlesnake	Mexico, on Tortuga Island, in the Gulf of California off the coast of Baja California Sur.
C. totonacus Crotalus totonacus Crotalus totonacus is a venomous pitviper species found in northeastern Mexico. No subspecies are currently recognized.-Description:Adults frequently grow to more than 150 cm in length...	Gloyd Howard K. Gloyd Howard Kay Gloyd was an American herpetologist who is credited with describing several new species of reptile, such as the Florida Cottonmouth, Agkistrodon piscivorus conanti...  & 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 Crotalus transversus Crotalus transversus is a venomous pitviper species found in central Mexico, known from less than 20 specimens. No subspecies are currently recognized.-Description:Adults grow to a maximum recorded length of 46.5 cm...	Taylor Edward Harrison Taylor Edward Harrison Taylor was an American herpetologist from Kansas.He was born in Maysville, Missouri and studied at the University of Kansas in Lawrence, Kansas, graduating with a B.A. in 1912. Subsequently, he went to the Philippines, where at first he held a teacher's post in a village in central... , 1944	0	Cross-banded mountain rattlesnake	Central Mexico in the states of México and Morelos Morelos Morelos officially Estado Libre y Soberano de Morelos is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 33 municipalities and its capital city is Cuernavaca.... .
C. triseriatus Crotalus triseriatus Crotalus triseriatus is a venomous pitviper species found in Mexico. Two subspecies are currently recognized, including the nominate subspecies described here.-Description:...	(Wagler Johann Georg Wagler Johann Georg Wagler was a German herpetologist.Wagler was assistant to Johann Baptist von Spix, and became Director of the Zoological Museum at the University of Munich after Spix's death in 1826... , 1830)	1	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. viridis Crotalus viridis Crotalus viridis is a venomous pitviper species native to the western United States, southwestern Canada, and northern Mexico. Currently, nine subspecies are recognized, including the nominate subspecies described here.-Description:...	(Rafinesque, 1818)	1	Prairie rattlesnake	Southern Canada (Alberta Alberta Alberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces... , Saskatchewan Saskatchewan Saskatchewan is a prairie province in Canada, which has an area of . Saskatchewan is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, and on the south by the U.S. states of Montana and North Dakota.... ), south through the United States (eastern Idaho, Montana Montana Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,... , North Dakota North Dakota North Dakota is a state located in the Midwestern region of the United States of America, along the Canadian border. The state is bordered by Canada to the north, Minnesota to the east, South Dakota to the south and Montana to the west. North Dakota is the 19th-largest state by area in the U.S.... , South Dakota South Dakota South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over... , Wyoming Wyoming Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High... , Nebraska Nebraska Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River.... , Colorado Colorado Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains... , Kansas Kansas Kansas is a US state located in the Midwestern United States. It is named after the Kansas River which flows through it, which in turn was named after the Kansa Native American tribe, which inhabited the area. The tribe's name is often said to mean "people of the wind" or "people of the south... , Oklahoma Oklahoma Oklahoma is a state located in the South Central region of the United States of America. With an estimated 3,751,351 residents as of the 2010 census and a land area of 68,667 square miles , Oklahoma is the 28th most populous and 20th-largest state... , Texas, New Mexico, extreme eastern Arizona), and into northern Mexico (northern Coahuila Coahuila Coahuila, formally Coahuila de Zaragoza , officially Estado Libre y Soberano de Coahuila de Zaragoza is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico... , northwestern Chihuahua).
C. willardi Crotalus willardi Crotalus willardi is a venomous pitviper species found in the southwestern United States and Mexico. It is the most recent rattlesnake species to be discovered in the United States. Its specific name is in honor of its discoverer, Professor Frank C. Willard. Five subspecies are currently...	Meek Seth Eugene Meek Seth Eugene Meek was an American ichthyologist at the Field Museum of Natural History in Chicago. He was the first compiler of a book on Mexican freshwater fishes. Together with his assistant, Samuel F. Hildebrand, he produced the first book on the freshwater fishes of Panama.He often collaborated... , 1905	4	Ridge-nosed rattlesnake	The United States in southeastern Arizona and southwestern New Mexico, and northwestern Mexico in Sonora, Chihuahua, Durango and Zacatecas.

• ) Not including the nominate subspecies.
  

^T) Type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

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See also

• List of crotaline species and subspecies
• Snakebite
  Snakebite
  A snakebite is an injury caused by a bite from a snake, often resulting in puncture wounds inflicted by the animal's fangs and sometimes resulting in envenomation. Although the majority of snake species are non-venomous and typically kill their prey with constriction rather than venom, venomous...
  
  

External links

• Crotalus at Herpbreeder.com. Accessed 26 September 2006.
• Sectioned rattle illustration at emilydamstra.com. Accessed 4 January 2007.
• Crotalus ruber Pictures of a crotalus in Baja California, Mexico.