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Plains Garter Snake

Thamnophis radix

What do they look like?

Plains garter snakes are long, striped garter snakes, usually from 40 to 70 cm long, but occasionally up to 109.5 cm. They have a dorsal and two lateral, yellow or orange stripes on a background scale color of dark brown to dark greenish. Lateral stripes are on scale rows 3 and 4. The sides may have some red pigmentation. Scales are keeled and measure 19 to 21 rows at the widest part of the body. There is a row of black spots between the lateral stripes and the scales on their belly. Males are slightly larger, with slightly longer tails. (Ernst and Ernst, 2003)

  • Sexual Dimorphism
  • male larger
  • sexes shaped differently
  • Range length
    109.5 (high) cm
    43.11 (high) in

Where do they live?

Plains garter snakes are found throughout the North American plains region, from the Oklahoma panhandle, northernmost Texas, and northeastern New Mexico north to southern Alberta, Saskatchewan, and Manitoba, and east through Minnesota, Wisconsin, and Indiana. (Ernst and Ernst, 2003)

What kind of habitat do they need?

Plains garter snakes are found in meadows, prairies, and other grasslands near sources of water, such as ponds, streams, marshes, and sloughs. They may also be found in swampy areas or along rivers. They may be found in suburban or urban vacant lots. Where they are found along with their close relative common garter snakes, they may be found in more dry habitats. This is because common garter snakes out-compete plains garter snakes for the more moist habitats. (Ernst and Ernst, 2003)

How do they grow?

Plains garter snakes grow approximately 1.1 cm per week during their first year, after which growth slows. (Ernst and Ernst, 2003)

How do they reproduce?

Males find females by using scent trails left by the females. Both males and females can mate with multiple individuals. (Ernst and Ernst, 2003)

Mating takes place after these snakes emerge from hibernation, in April or May. Plains garter snakes give birth to live young from June through September, after a gestation period of 83 to 102 days. There are from 5 to 60 young in a litter, but usually 10 to 20. (Ernst and Ernst, 2003)

  • How often does reproduction occur?
    Plains garter snakes breed once yearly.
  • Breeding season
    Plains garter snakes breed in April or May.
  • Range number of offspring
    5 to 60
  • Average number of offspring
    10-20
  • Range gestation period
    83 to 102 days
  • Range age at sexual or reproductive maturity (female)
    2 to 3 years

Females give birth to live young. After the young are born, they do not need the help of either parent. (Ernst and Ernst, 2003)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female

How long do they live?

A captive plains garter snake was recorded living to almost 8 1/2 years. (Ernst and Ernst, 2003)

  • Range lifespan
    Status: captivity
    8.5 (high) years

How do they behave?

Plains garter snakes are active from March to November, depending on the region. They may be active for shorter periods in northern portions of their range. They hibernate in burrows or rock crevices, although they may emerge on warm, winter days. They often hibernate in rodent burrows or ant mounts, but have also been found in crayfish burrows, under sidewalks, in other man made crevices, and even underwater. They are active during the day at warm temperatures, usually between 21 and 29 degrees Celsius. Once the air temperature goes above 31 degrees Celsius, these garter snakes switch their active period to night time. At much lower temperatures, prairie garter snakes become inactive. These snakes are solitary. (Ernst and Ernst, 2003)

Home Range

Plains garter snakes stay within relatively small home ranges for long periods of time, moving only up to 76 meters over periods of over a year. (Ernst and Ernst, 2003)

How do they communicate with each other?

Plains garter snakes use their sense of smell mostly. They find prey, mates, and hibernation sites by following scent trails. They also use vision and vibrations to help find their way around, avoid predators, and find prey. (Ernst and Ernst, 2003)

What do they eat?

Plains garter snakes eat a wide variety of animal prey. The diet of plains garter snakes and common garter snakes is very similar, so they probably compete for prey where they are found in the same area. They eat frogs and toads, salamanders, fish, birds, small rodents, leeches, earthworms, and grasshoppers. Amphibians eaten include northern cricket frogs, American toads, great plains toads, tree frogs, striped chorus frogs, plains leopard frogs, northern leopard frogs, and various salamanders. They also eat mosquitofish, southern redbelly dace, bluntnose minnows, bank swallows, and eastern meadowlarks. Plains garter snakes find prey by following scent trails, then grabbing prey once they catch up with them. (Ernst and Ernst, 2003)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • fish
  • insects
  • terrestrial worms

What eats them and how do they avoid being eaten?

Plains garter snakes may be preyed on by birds of prey, such as red-shouldered hawks, Swainson's hawks, kestrels, and northern harriers. Other predators include foxes, coyotes, striped skunks, mink, domestic cats, and milk snakes. Humans also sometimes kill prairie garter snakes. These garter snakes will bite, emit a foul smell, or defecate to discourage predators. Their lateral stripes make them difficult to see in their grassy habitats and as they move. Plains garter snakes also have a series of antipredator displays that they will use, including hiding their heads, striking with the mouth closed or open, coiling or balling up their bodies, extending the body flat, and waving the tail. (Ernst and Ernst, 2003)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Plains garter snakes are important predators of amphibians, earthworms, leeches, and other animals in their prairie habitats. (Ernst and Ernst, 2003)

Do they cause problems?

There are no adverse effects of plains garter snakes on humans. These are nonvenomous snakes that are shy and retiring, in general, although they will bite if threatened. (Ernst and Ernst, 2003)

How do they interact with us?

Plains garter snakes are important members of the native prairie habitats they are found in.

Are they endangered?

Plains garter snakes are not considered threatened, although regional populations may be vulnerable. They are considered endangered in Ohio and a species of concern in Arkansas. (Ernst and Ernst, 2003)

Some more information...

Contributors

George Hammond (editor), Animal Diversity Web Staff.

Tanya Dewey (author), University of Michigan-Ann Arbor.

References

Ernst, C., E. Ernst. 2003. Snakes of the United States and Canada. Washington, D.C.: Smithsonian Books.

Harding, J. 2000. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: University of Michigan Press.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Dewey, T. 2011. "Thamnophis radix" (On-line), Animal Diversity Web. Accessed July 22, 2014 at http://www.biokids.umich.edu/accounts/Thamnophis_radix/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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