Natural History: Thamnophis sirtalis

The other day, I received a phone call from my mom, frantic, because there was a snake by the garage. She described it to me and sent me a picture, and I recognized it as an Eastern Garter snake (Thamnophis sirtalis). This snake is from the family of Natricidae, the harmless live-bearing snakes (although that didn't give my mom much comfort!) I couldn't get the picture she sent me off of my phone, but this specimen is a close match:

source

source

The snake was described as about a foot long and a thumb's width in diameter. Typically, garter snakes are 18-26 inches, so this one is likely to be young. She said it was black with yellow stripes, but its belly was yellow with black stripes. In addition, T. sirtalis has black lines around its mouth, which differs from T.sauritus, the Eastern Ribbon Snake (look closely in the above photo to see the mouth stripes). Another way to tell garter snakes from ribbon snakes is that garter snakes have their lateral stripes on scales rows 2 and 3; ribbon snakes have them on rows 3 and 4. Thamnophis have single anal plates and keeled scales. Garter snakes typically eat frogs, toads, and salamanders, with the occasional earthworm or fish. They may give off an odor from their cloaca when caught, in an attempt to turn predators away; they can also bite, but it, too, is harmless to humans.

This snake was seen in the upstate of SC, sunning itself on a stone, mid-afternoon, on a sunny day, with a high temperature around 80 degrees F. There are ponds within a mile of my home, as well as lots of dense foliage/trees.

To breed, garter snakes form mating balls, in late March until early May. They give birth to live young in the summertime.

source

At least my mom did not see one of these!