plains garter snake

(Thamnophis radix)

Conservation Status

IUCN Red List

LC - Least Concern

plains garter snake


N5 - Secure

S5 - Secure


not listed




Moist, open places. Prairies, meadows, farmlands, and other open areas near water.


5 to 10 years


14 to 43 long

    Photo by Bill Reynolds


This is a medium-sized, nonvenomous, typical snake. It can be from 14 to 43 long at maturity, though it is usually no more than 28 in length. Males are slightly larger than females.

The background color is variable and may be light brown to black or olive green. There are three pale stripes that run the length of the body. The central stripe is usually bright yellow or orange, sometimes orange near the head and then yellow to the tail. The lateral stripes are cream-colored to pale yellowish, and are on the third and fourth scale rows counting up from the belly (ventral) scales. There are two rows of alternating black spots on each side between the central and lateral stripes. The spots may be prominent and invade the stripes, or may be obscured on dark colored individuals. Red skin may be visible between the scales when it stretched over recently consumed prey, but there are no red scales. At mid-body there are 19 to 21 rows of scales. The upper (dorsal) and lateral scales have a narrow raised ridge (keel) along the centerline.

The belly is white and may be tinted yellowish or bluish. There is usually a row of small black spots at the ends of the ventral scales. These spots are partially hidden by overlapping ventral scales. The anal plate is not divided. Underneath the tail there are two rows of scales (subcaudal scales).

The head and neck are uniformly dark usually with a pair of yellow spots. All of the scales above the mouth (labial scales) are the same color as the lateral stripe and have a bold black border.


Eastern garter snake (Thamnophis sirtalis sirtalis) lateral pale stripes are on the second and third scale rows counting up from the ventral scales. None or at most one or two of the labial scales have a bold black border.

Lined snake (Tropidoclonion lineatum) is much shorter, only 8 to 12 long at maturity. The 3 stripes are off-white. There are 2 rows of dark, half-moon marks on the belly. In Minnesota it has been found only in Blue Mounds State Park.

Red-sided garter snake (Thamnophis sirtalis parietalis) has bold red bars or spots on the side between the dorsal and lateral scales.


Earthworms, amphibians, leeches, slugs, snails, insects, crayfish, small fish, bird eggs, mice, other snakes, and carrion.

Life Cycle

Overwintering plains garter snakes emerge from their overwintering sites in March. Females reach sexual maturity in 2 or 3 years. Breeding takes place in April or May. Gestation takes 83 to 102 days. In July to September the female gives birth to a litter of 4¾ to 9½ long, live young. The litter size is usually 10 to 20 but may be as few as 5 or as many as 60. The young are on their own from the day of their birth.

In late October they gather in large numbers, sometimes with other species of snakes, in rodent burrows, abandoned ant mounds, or under sidewalks, to overwinter. As the temperature drops they enter a state of suspended animation (brumation).



Distribution Distribution Map   Sources: 7, 11, 14, 24, 29, 74.





Squamata (amphisbaenians, lizards, and snakes)






Serpentes (snakes)






Colubridae (colubrids, typical snakes)







plains garter snake








Anal plate

In snakes: the large scale in front of and covering the anus. In turtles: one of the posterior plates of the lower shell (plastron). In Lepidoptera: the often hardened shield on the dorsal surface of the last (10th) segment of the abdomen.


Ventral scales

On snakes, the row of enlarged, elongated scales extending on the belly from the neck to the anal plate.



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Bill Reynolds

  plains garter snake    











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Other Videos

  Plains Garter Snake (Colubridae: Thamnophis radix) Scale Pattern
Carl Barrentine

Uploaded on Jun 26, 2009

In this species (T. radix) the lateral stripe is confined to scale rows 3 and 4, whereas is T. sirtalis, another local species of garter snake, the lateral stripe is confined to rows 2 and 3. Photographed at Turtle River State Park, North Dakota (26 June 2009). " I saw a young snake glide / out of the molted shale / And hang, limp on a stone: / A thin mouth, and a tongue / Stayed, in the still air. / It turned: it drew away; / It's shadow bent in half : / It quickened, and was gone. / I felt my slow blood warm. / I longed to be that thing, / the pure, sensuous form. / And I maybe, some time." --Theodore Roethke

  A Nature Video: Plains Garter Snake

Published on May 6, 2013

A Nature Video: Plains Garter Snake

Plains Garter Snakes (Thamnophis radix) are native to much of central United States and parts of Canada. They are listed as "Least Concern" although they are of special concern in Wisconsin, and endangered in Ohio. They can be found in fields, prairies, woodlands, forests, marshes, and on occasion, in your own backyard. They are often found around bodies of water such as streams, rivers, and ponds.

Plains Garter Snakes have a yellow or orange stripe down their back, as well as small black stripes under their eyes. They also have a black and brown checkered pattern down their backs. Adults can range from 2.5 to 4 feet long. They eat earthworms, minnows, and amphibians including toads, frogs, and salamanders.

This video was shot in the woods of Smolenski Park in Racine Co., Wisconsin. No animals were harmed in the making of this video and both snakes were released after filming, or more accurately, during filming (at 2:20).

If you go looking for snakes, be sure to know if there are any venomous snakes in your area, and memorize what they look like. Never handle a venomous snake.

Its important to note that many reptiles and amphibians are losing their habitat on a daily basis. Many that were common 50 years ago are not threatened or endangered. Their map ranges are shrinking all the time. Its important as human beings to do all we can to protect these animals before its too late.

  The Plains Garter Snake (Colubridae: Thamnophis radix)
Carl Barrentine

Uploaded on Dec 20, 2009

A contemplative look at the beauty of a much maligned species. The plains garter snake (Thamnophis radix) is a common but seldom seen species in the upper midwest of the United States. Specimens shown here were filmed in northeastern North Dakota and northwestern Minnesota in the late summer and fall, 2009.





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Bill Reynolds

Location: Caribou, Kittson Co. MN

plains garter snake






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