Plains Garter Snake
Thamnophis radix

by Jeff LeClere

Status

No status assigned in Minnesota.

Description

The plains garter snake is a medium sized Minnesota snake measuring 14 to 43 inches in length. It is non-venomous and can be more docile than the common garter snake. The ground color is light brown to black with two alternating rows of black spots. Some specimens have an olive green background color in which the spots stand out especially well. There are three longitudinal stripes. The dorsal stripe is usually yellow or orange; some having an orange stripe anteriorly that changes to yellow before mid body and remains yellow to the tip of the tail. The lateral stripes are cream to yellow and are located on the third and fourth scale rows. There is usually a row of black spots below the lateral stripes at the edge of the ventral scales. The belly may be white, yellowish, or bluish. The head is brown or black with one or two small yellow dots near the parietals scales atop the head (these may be absent) and dark black bars on the labial scales. The scales are keeled and the anal plate is single.

Subspecies

There are two weakly defined subspecies of the plains garter snake, both are found in Minnesota. The eastern plains garter snake, Thamnophis radix radix, usually has 19 scale rows on the neck and 154 or fewer ventral scales. The western plains garter snake, Thamnophis radix haydeni, which usually has 21 or more scale rows on the neck and 155 or more ventral scales. There are differences in coloration and the western race has smaller dorsal spots, but this is not always consistent. These two subspecies intergrade heavily in Minnesota and specimens resembling either subspecies may be found outside of their repective ranges. Additionally, the the most striking, obvious geographical morphological changes occur much farther west than the described subspecies' ranges presently show.

Range

The eastern plains garter snake is supposedly found in the southeastern counties of Minnesota while the western plains garter snake inhabits the western prairie portions of the state.

Habitat

The plains garter snake is one of Minnesota's most common snakes. They occur almost anywhere there is adequate food and shelter. They are extremely adaptable to environmental changes like the common garter snake. Unlike the common garter snake, however, the majority prefer drier habitats, though a few individuals may be found at the waters' edge. Open plains or grasslands on forest edges are favorite natural haunts. City parks, vacant lots, farmlands, or suburban backyards are also utilized.

Habits

This is a diurnal, active snake that is usually much less aggressive than the eastern or red-sided garter snake (common garter snake). Instead of biting, it often expels a foul smelling musk and excretement to dissuade enemies. If cornered, it may hide its head under its coils, raise its tail in the air, and slowly wag its tail back and forth. They are active thermoregulators and will alternately hunt and bask throughout the day. They take refuge underneath logs, rocks, boards, and in mammal burrows. They breed in the spring and the young are born alive in late summer or autumn. There may be 10-70 or more in a litter and are 5-8 inches in length. They may hibernate with other species of snakes and use any place they can get below the frost line. Road embankments, mammal burrows, and basements are common hibernaculums. Young plains garter snakes may hibernate with redbelly and green snakes in abandoned ant mounds.

Food

Plains garter snakes are voracious feeders and will eat anything they can catch and swallow, especially when warm. Earthworms, fish, frogs, toads, salamanders, mice, and birds' eggs are consumed. These snakes may eat carrion. They eat their prey without constriction or venom, thus they have strong jaws to overpower their prey.