Common names: prairie rattlesnake, western rattlesnake, plains rattlesnake, more.

Crotalus viridis is a 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...

 pitviper

Crotalinae

The Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 native to the western United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, southwestern 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...

, and northern 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...

. Currently, nine subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 are recognized, including the nominate subspecies described here.

Description

This species commonly grows to more than 100 cm in length. The maximum recorded size is 151.5 cm (Klauber, 1937). In 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,...

, specimens occasionally exceed 120 cm in length; Klauber (1972) mentioned that the species reaches its maximum size in this region. One of the most characteristic features is the presence of three or more, usually four, internasal scales

Internasal scales

In snakes, the internasal scales are those on top of the head between the scales that surround the nostrils. They are usually paired and situated just behind the rostral....

.

Identification

Identification characteristics will vary depending on which subspecies is encountered. Generally, western rattlesnakes are usually lightly colored in hues of brown. Patches of dark brown are often distributed in a dorsal pattern. A color band may be seen at the back of the eye. The western rattlesnake group carries the distinctive triangular-shaped head and pit sensory organs on either side of the head. A key characteristic that can help differentiate a western rattlesnake from other rattlesnakes is the presence of two internasals contacting the rostral.

Diet

Western rattlesnakes, because of their expansive distribution, have a wide array of prey items. Generally, this species prefers small mammals such as ground squirrels, mice, rats, small rabbits and prairie dogs. They will occasionally feed on amphibians and reptiles. This is more commonly seen in juvenile snakes.

Reproduction

Western rattlesnakes are viviparous and can produce anywhere from 1 to 25 young per reproduction event. The average number of young ranges from 4-12 but can vary greatly due to availability of food and environmental conditions. Western rattlesnake females may not necessarily breed every year C. viridis. It is also common for females to give birth at communal den sites. The young are born between the months of August and October.

Behavior

Western rattlesnakes are typically active diurnally in cooler weather and nocturnally during hot weather C. viridis. This species complex is equipped with powerful venom and will defend if threatened or injured. As with other rattlesnake species, western rattlesnakes will rapidly vibrate their tail which produces a unique rasping sound to warn intruders.

Common names

Prairie rattlesnake, western rattlesnake, plains rattlesnake, black rattler, prairie rattler, common rattlesnake, confluent rattlesnake, Great Basin rattlesnake, large prairie rattlesnake, Missouri rattlesnake, rattlesnake of the prairies, spotted rattlesnake, Western Pacific Rattlesnake.

Geographic range

Found 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...

 over much of the Great Plains

Great Plains

The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...

, from south western 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...

 south through the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 to northern 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...

. In Canada it occurs in 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...

 and 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....

; in the USA in eastern 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....

, eastern 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...

, eastern Washington, 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

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...

, 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...

, extreme eastern 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 Mexico in 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...

 and northwestern Chihuahua. Its vertical range from 100 m near the Rio Grande River to over 2,775 m elevation in Wyoming.

Wright and Wright (1957) and Klauber (1997) both mention 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...

 as within the range of this species, including maps showing it confined to the extreme southeastern part of the state.

The type locality is described as "the Upper Missouri" (Valley, USA). An emendation was proposed by Smith and Taylor (1950) to "Gross

Gross, Nebraska

Gross is a village in Boyd County, Nebraska, United States. As of the 2010 census, the village had a total population of 2, down from its 2000 population of five...

, Boyd County, Nebraska

Boyd County, Nebraska

Boyd County is a county located in the U.S. state of Nebraska. As of 2010, the population is 2,099. Its county seat is Butte.In the Nebraska license plate system, Boyd County is represented by the prefix 63 .-Geography:According to the U.S...

."

Conservation status

This species is classified as Least Concern (LC) on the IUCN

World Conservation Union

The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...

 Red List of Threatened Species

IUCN Red List

The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...

 (v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend is stable. Year assessed: 2006.

Subspecies

Subspecies	Taxon author	Common name	Geographic range
C. v. nuntius Crotalus viridis nuntius Crotalus viridis nuntius is a venomous pitviper subspecies native primarily to the desert plateau of the northeastern portion of the American state of Arizona, but also ranges into northwestern New Mexico. Named for the Native American Hopi tribe, which inhabits the region, its range overlaps that...	Klauber Laurence Monroe Klauber Laurence M. Klauber , was an American herpetologist, and was considered to be the foremost authority on rattlesnakes... , 1935	Hopi rattlesnake	The United States United States The United States of America is a federal constitutional republic comprising fifty states and a federal district...  from northeastern and north-central 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... , from the New Mexican 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...  line to Cateract Creek, including the Little Colorado River Little Colorado River The Little Colorado River is a river in the U.S. state of Arizona, providing the principal drainage from the Painted Desert region. Together with its major tributary, the Puerco River, it drains an area of about in eastern Arizona and western New Mexico...  basin, the southern section of the Apache Indian Reservation, the Hopi Reservation Hopi Reservation The Hopi Reservation, or simply Hopi, is a Native American reservation for the Hopi and Arizona Tewa people, surrounded entirely by the Navajo Nation, in Navajo and Coconino counties of Arizona, USA. The site in north-eastern Arizona has a land area of 2,531.773 sq mi and as of the 2000 census had... , and the Coconino Plateau Coconino Plateau The Coconino Plateau is found south of the Grand Canyon and north—northwest of Flagstaff, in northern Arizona of the Southwestern United States.-Geography:...  from the southern rim of the Grand Canyon Grand Canyon The Grand Canyon is a steep-sided canyon carved by the Colorado River in the United States in the state of Arizona. It is largely contained within the Grand Canyon National Park, the 15th national park in the United States...  to U.S. Highway 66 U.S. Route 66 U.S. Route 66 was a highway within the U.S. Highway System. One of the original U.S. highways, Route 66 was established on November 11, 1926 -- with road signs erected the following year...  in the south.
C. v. viridis	(Rafinesque, 1818)	Prairie rattlesnake	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... n Great Plains Great Plains The Great Plains are a broad expanse of flat land, much of it covered in prairie, steppe and grassland, which lies west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...  from the Rocky Mountains Rocky Mountains The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...  to long. 96° W. and 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 extreme northern 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... , including southwestern 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.... , southeastern 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... , eastern Washington, 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....  in the Lemhi Valley, 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,...  east of the higher Rockies Rocky Mountains The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States... , southwestern 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.... , west, central and extreme southeastern 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... , western Iowa Iowa Iowa is a state located in the Midwestern United States, an area often referred to as the "American Heartland". It derives its name from the Ioway people, one of the many American Indian tribes that occupied the state at the time of European exploration. Iowa was a part of the French colony of New... , central and western 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.... , 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...  except for the Rockies, 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... , central and western 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... , extreme southeastern 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... , northeastern 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... , 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... , western and southwestern 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... , northeastern 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.... , northern Chihuahua, 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... .

Taxonomy

The taxonomic history of this species is convoluted. Previously, seven other C. viridis subspecies were also recognized, including abyssus, caliginis

Crotalus oreganus caliginis

Crotalus oreganus caliginis is a venomous pitviper subspecies endemic to South Coronado Island, Mexico.-Geographic range:Known only from the type locality, given as "South Coronado Island, off the northwest coast of Baja California, Mexico."...

, cerberus

Crotalus oreganus cerberus

Crotalus oreganus cerberus is a venomous pitviper subspecies found in the southwestern United States.-Description:According to Wright and Wright , adults grow to an average length of 78-109 cm...

, concolor

Crotalus oreganus concolor

Crotalus oreganus concolor is a venomous pitviper subspecies found in the western United States. A small species known for its faded color pattern.-Description:Grows to a maximum length of 750 mm...

, helleri, lutosus

Crotalus oreganus lutosus

Crotalus oreganus lutosus is a venomous pitviper subspecies found in the Great Basin region of the United States.-Description:Adult specimens are 66-121 cm in length, but rarely exceed an overall length of 1 m...

 and 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....

. However, in 2001 Ashton and de Queiroz published a paper describing their analysis of the variation of mitochondrial DNA

Mitochondrial DNA

Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 across the range of this species. Their results agreed broadly with those obtained by Pook et al. (2000). Two main clade

Clade

A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

s were identified, east and west of the Rocky Mountains

Rocky Mountains

The Rocky Mountains are a major mountain range in western North America. The Rocky Mountains stretch more than from the northernmost part of British Columbia, in western Canada, to New Mexico, in the southwestern United States...

, which they argued were actually two different species: on the one hand C. viridis, including the conventional subspecies viridis and nuntius

Crotalus viridis nuntius

Crotalus viridis nuntius is a venomous pitviper subspecies native primarily to the desert plateau of the northeastern portion of the American state of Arizona, but also ranges into northwestern New Mexico. Named for the Native American Hopi tribe, which inhabits the region, its range overlaps that...

, and on the other 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....

, including all the other traditional subspecies of C. viridis. The authors retained the names of the traditional subspecies, but emphasized the need for more work to be done on the systematics

Systematics

Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...

of C. oreganus.

External links

• Prairie Rattlesnake - Crotalus viridis at Herpnet.net, Reptiles and Amphibians of Iowa. Accessed 15 June 2007.