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Crotalus viridisviridis

By Harry Russell

Geographic Range

Prairie rattlesnakes, Crotalus viridis, are found throughout the midwestern United States and extend from southwest Canada to the northwest part of Mexico. In Canada, prairie rattlesnakes are native to the southern provinces of Alberta and Saskatchewan. They are also in the northern part of Chihuahua, Mexico. Their range covers much of New Mexico, Colorado, Wyoming, and Montana in the United States, as well as northeast Texas, and the eastern borders of Nebraska, Arizona, and the Dakotas. (Frost, et al., 2007; Sweet, 1985; Zug and Ernst, 2004)

Habitat

Prairie rattlesnakes are found in environments ranging from 100 to 2700 feet in elevation and in settings that are rocky or rugged, as well as open fields that are heavily populated with prey. Prairie rattlesnakes are also found in forests because of the forest debris on the ground that can be used for protection. Many of their prey can also be found in dry grasslands and chaparrals. The chaparrals have various amounts of shrubs and vegetation that can be used to help prairie rattlesnakes be camouflaged for hunting. The main characteristic of prairie rattlesnake habitat are environments that have burrows formed from rocks, under branches, and holes dug by other animals. (Campbell and Lamar, 2004; Shipley, et al., 2013; Stebbins, 2003; Sweet, 1985)

  • Range elevation
    100 to 2700 m
    328.08 to 8858.27 ft

Physical Description

Prairie rattlesnake adults range between 45.3 and 165 cm in length and weigh 227 to 361 g. They possess a light brown to black tint on their dorsum and a yellow stripe located on their head. The prairie rattlesnakes' ventral side often blends with the ground to serve as camouflage. The most common colors found on their ventral sides are tan, a yellowish shade, or gray. The prairie rattlesnakes' surroundings are lighter blends of colors; to help complement this camouflage, there can also be patterned stripes or blotches on their body.

Male and female prairie rattlesnakes share the same physical characteristics. A characteristic to differentiate prairie rattlesnakes from other species of snakes is that prairie rattlesnakes have two or more nasal scales where other species of snakes only have one. Prairie rattlesnakes also have solenoglyphous teeth to transmit their venom. The teeth can range from 0.56 to 0.99 cm in length.

Male juveniles have an average size of 28.5cm in length, and females have an average size of 28.2cm.

There are seven subspecies of the prairie rattlesnakes, which differ in appearance. These include Grand Canyon rattlesnakes (Crotalus oreganus abyssus) which have a red color on the dorsum with darker ovals. Coronado Island rattlesnakes (Crotalus oreganus caliginis) stay a grayish color all over their body and are typically smaller in size, averaging 25cm long as adults. Arizona black rattlesnakes (Crotalus viridis ceberus) have darker shades on their body such as gray or black patches on the dorsum. Midget faded rattlesnakes (Crotalus oreganus concolor) have a pinkish tone to their scales. Southern Pacific rattlesnakes (Crotalus oreganus helleri) remain lighter in shades of colors such as tan and yellow as well as having dark brown patches on the body and a wide tail. Great Basin rattlesnakes (Crotalus oreganus lutosus) are thick-bodied and have tan coloring along with black patches on the dorsum. Hopi rattlesnakes (Crotalus oreganus) have pink and red shades on their scales, with brown patches all over the body. (Charland and Gregory, 1990; Klauber, 1939; Macartney, et al., 1990; Stebbins, 2003; William and William, 1974)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    227 to 361 g
    8.00 to 12.72 oz
  • Range length
    25 to 165 cm
    9.84 to 64.96 in

Development

Prairie rattlesnakes have offspring by laying amniotic eggs with linings of extra membranes for protection. Within the egg, the nutrients are supplied to the embryo by a yolk sac that is attached to the digestive tracts. Prairie rattlesnakes are viviparous, with females giving birth to up to 25 live young. Prairie rattlesnakes exhibit indeterminate growth. Male prairie rattlesnakes have a faster growth rate at a younger age compared to females. Males have a growth rate of 535 mm in 3 to 4 years while females grow 650 mm from 5 to 7 years. (Linzey, 2012; Macartney, et al., 1990; Shine and Charnov, 1992)

Reproduction

Prairie rattlesnakes have a mating season of about 7 weeks between July-September. During this period, the males seek out the females to reproduce. The female snakes are scarce because only about 31% of female snakes are in heat during each mating period. Female snakes are considered monogamous during a single season but will seek out a different mate the following season. There are no relationships between mates and very little competition occurs between male snakes when a female is present. Because competition between males is at a minimum, females do not take physical characteristics into account when choosing a mate. ("COSEWIC assessment and status report on the Prairie Rattlesnake Crotalus viridis in Canada", 2015; Duvall and Shuett, 1997; Linzey, 2012; Zug and Ernst, 2004)

Prairie rattlesnakes are iteroparous and the mating season is about 7 weeks from July to September. Males have two sexual organs called hemipenes that are stored inside of the hemipenal sheath, and they are everted to mate. The hemipenes have a hooked shape to help attach to the female reproductive organs. The hemipenes are inserted into the female's cloaca and the sperm are released internally. Prairie rattlesnakes are oviparous and can lay 4 to 21 eggs with the gestation lasting from 3 to 4 months. Prairie rattlesnakes hare independent upon hatching and reach sexual maturity after 2 to 3 years. ("COSEWIC assessment and status report on the Prairie Rattlesnake Crotalus viridis in Canada", 2015; Aldridge and Sever, 2011; Linzey, 2012; Stebbins, 2003)

  • Breeding interval
    They breed once a year
  • Breeding season
    Approximately a 7-week season between July and September
  • Range number of offspring
    4 to 21
  • Range gestation period
    3 to 4 months
  • Average time to independence
    0 minutes
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years
  • Range age at sexual or reproductive maturity (male)
    2 to 3 years

Once female prairie rattlesnakes lay the eggs, they guard the eggs by coiling up around them. By coiling around the eggs, the prairie rattlesnakes can increase the temperature of the body by contracting muscles. The temperature can increase up to 7.5° Celsius which helps with the incubation of the eggs. The incubation takes about 5 to 16 weeks. Once the eggs are hatched, the female ends up leaving and the newly-hatched prairie rattlesnakes have no parental care. ("COSEWIC assessment and status report on the Prairie Rattlesnake Crotalus viridis in Canada", 2015; Linzey, 2012; Stebbins, 2003; Zug and Ernst, 2004)

  • Parental Investment
  • female parental care
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female

Lifespan/Longevity

The average expected lifespan for prairie rattlesnakes ranges between 16 and 20 years in the wild. The maximum known lifespan in captivity was 24.1 years. The main factor that limits the lifespan is being hunted by predators such as red-shouldered hawks (Buteo lineatus) and greater roadrunners (Geococcyx californianus). (Bowler and Snider, 1992)

  • Range lifespan
    Status: captivity
    24.1 (high) years
  • Typical lifespan
    Status: wild
    16 to 20 years
  • Average lifespan
    Status: captivity
    24.1 years
    AnAge

Behavior

Prairie rattlesnakes only show aggression when they are threatened. To detect if there are prey or predators in the area, prairie rattlesnakes use tongue flicking to pick up on chemical cues left behind. They also perceive in infrared spectrum and can see the heat that radiates from their surroundings. There is no social hierarchy within this species, as these snakes remain solitary throughout their lives.

Prairie rattlesnakes most commonly hunt during the colder parts of the summer days such as dusk and dawn. These snakes are nocturnal when daytime ambient temperatures are extremely hot. In winter months prairie rattlesnakes hibernate. Prairie rattlesnakes are not migratory but travel as far as 10 kilometers for a den in which to hibernate. The length of hibernation is dependent on location. Prairie rattlesnakes that live in South Dakota endure a longer and more extreme winter compared to snakes living in Texas. Prairie rattlesnake hibernation can nearly double in time in the northern regions because of this climate factor. ("COSEWIC assessment and status report on the Prairie Rattlesnake Crotalus viridis in Canada", 2015; Charland, 1989; Chiszar, et al., 1978; Duvall, et al., 1990; Golan, et al., 1982; Zug and Ernst, 2004)

Home Range

Prairie rattlesnakes, on average, stay within a 0.04 to 0.21 square kilometer range. Many of the prairie rattlesnakes can be found within 1 meter of a burrow of some sort used for nesting and will get aggressive if they are threatened or if another species enters their home range. These burrows were made by a mammal or animal that has abandoned it. ("COSEWIC assessment and status report on the Prairie Rattlesnake Crotalus viridis in Canada", 2015)

Communication and Perception

Prairie rattlesnakes have a weak sense of sight. They are able to detect any object that emits heat. Prairie rattlesnakes rely heavily on their smell and tactile senses. Prairie rattlesnakes have a strong sense of chemical detection that helps them hunt prey. In order to detect the different chemical cues emitted by prey and other snakes, the use of the tongue acts a sense of smell so they know what is in their surroundings. They are able to detect potential prey and other snakes for possible reproduction. Potential prey also leave specific hormones and chemicals behind that can be easily detected as a scent to prairie rattlesnakes. These scents are transferred from the tongue to the vomeronasal organ in the mouth. The vomeronasal organ contains receptors that take the scent and interprets it as a smell. Using their tongues, male prairie rattlesnakes can also detect a sex pheromone released by females during the mating season. (Chiszar, et al., 1978; Chiszar, et al., 1983; Cooper, 1993; Daghfous, et al., 2012; Gillingham and Clark, 1981; Newman and Hartline, 1982; Shine and Mason, 2012)

Food Habits

The prairie rattlesnake diet consists of rodents such as voles (Microtus species), deer mice (Peromyscus species), smooth-toothed pocket gophers (Thomomys species), chipmunks (Tamias species), woodrats (Neotoma species), and red squirrels (Tamiasciurus species). About 60% of the adult prairie rattlesnake diet is composed of voles and deer mice. Prairie rattlesnakes will also eat birds, any type of eggs found, and even other reptiles, but they will typically not eat anything larger than black-tailed prairie dogs (Cynomys ludovicianus). In subduing prey, these rattlesnakes use a potent venom. The strike is so quick and accurate that it stuns the prey. The coiling of the body is what makes prairie rattlesnakes so dangerous because it generates power and helps account for minimal striking error. The jaws are able to re-correct the fang position to account for any attempt of escape from the prey.

Juvenile prairie rattlesnakes do not have the same type of diverse diet as adult prairie rattlesnakes. About 92.5% of a juvenile's diet is composed of shrews (Sorex species), deer mice, and voles. (Cooper, 2017; Kardong and Bels, 1998; Kardong and Rochelle, 1996; MacArtney, 1989; Reimer and Petras, 1967; Stebbins, 2003)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles
  • eggs

Predation

Many birds prey on prairie rattlesnakes, including raptors like red-shouldered hawks (Buteo lineatus). Greater roadrunners (Geococcyx californianus) are also common predators. Greater roadrunners kill them by pecking them repeatedly in the head. They feed on snakes so often that they are given the name snake killers. Prairie rattlesnakes use their tail to rattle and warn the predator that they are venomous. The venom can cause hemorrhaging and necrotic damage. On top of rattling and being venomous, their cryptic coloration allows for prairie rattlesnakes to blend with the surroundings by using dark brown blotches with tan and yellowish shades on the dorsum. (Cameron and Tu, 1977; Campbell and Lamar, 2004; Fenton and Lawrence, 1990; Zug and Ernst, 2004)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Prairie rattlesnakes, prey on rats and mice. Predators of these rattlesnakes include red-shouldered hawks (Buteo lineatus), and greater roadrunners (Geococcyx californianus). Prairie rattlesnakes serve as a host for parasitic worms called helminths. Species of helminths include: Rhabdias, Kalicephalus inermis coronelías, Physaloptera (3rd-stage larvae), and Oochoristica osheroffi. (Fenton and Lawrence, 1990; Meerburg, et al., 2009; Widmer, 1967; Zug and Ernst, 2004)

Commensal/Parasitic Species
  • helminths (Rhabdias)
  • helminths (Kalicephalus inermis coronelías)
  • helminths (Physaloptera)
  • helminths (Oochoristica osheroffi)

Economic Importance for Humans: Positive

Prairie rattlesnake skin can be used for the manufacturing of clothing items such as boots, ties, and belts as well as bags. Prairie rattlesnake meat is expensive in the U.S. and can be used for trade. (Fitzgerald and Painter, 200)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

Prairie rattlesnakes will strike and bite when provoked. Prairie rattlesnakes release a polypeptide myotoxin and if bitten, hemorrhaging and necrotic damage to muscle tissues, myonecrosis, occurs. The antivenin is composed of anti-myotoxin serum and a polyvalent that can help neutralize the effects of hemorrhaging and myonecrosis caused by the venom. (Cameron and Tu, 1977; Campbell and Lamar, 2004; Ownby, et al., 1986)

  • Negative Impacts
  • injures humans

Conservation Status

Prairie rattlesnakes are listed as a species of Least Concern and has no special status on the US Federal List, government lists in the United States or internationally (CITES). In the midwestern U.S., where there are residential and commercial expansions, populations have been extinguished when dens and habitats are eradicated. There are no known conservation measures in place. (Fitzgerald and Painter, 200; Frost, et al., 2007)

Contributors

Harry Russell (author), Radford University, Alex Atwood (editor), Radford University, Karen Powers (editor), Radford University, Joshua Turner (editor), Radford University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

female parental care

parental care is carried out by females

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

infrared/heat

(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

venomous

an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).

visual

uses sight to communicate

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