Plains garter snake

Description

Plains garter snake 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. Females are slightly longer and significantly heavier than males.

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 usually all of them have a bold black border.

Size

Total length: 14″ to 43″

Similar Species

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.

Habitat

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

Ecology

Behavior

Lifespan

5 to 10 years

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).

Food

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

Toxicity

Plains garter snakes are venomous but their venom is not strong enough to cause serious harm to humans. Allergic reactions to a bite from a common garter snake are rare. Reaction to a bite is normally little more than swelling and irritation around the puncture wound. However, like a bite from any animal, bacteria from the mouth of the snake can cause an infection.