There are several subspecies of garter snakes found in the range of this work.
EASTERN BLACKNECK GARTER SNAKE
They feed primarily on toads and frogs. I have seen juveniles swimming underwater in pursuit of tadpoles.
Thamnopohis cyrtopsis ocellatus
In the range of this work, the eastern blackneck garter snake is found from Val Verde county west to eastern Brewster county. Although it is common in the eastern part of its range, it is only occasionally encountered in the range of this work.
This specimen is from highway 277, northeastern Val Verde County.
WESTERN BLACKNECK GARTER SNAKE
Thamnophis cyrtopsis cyrtopsis
The western blackneck garter snake is found in the western part of the state, roughly in the portion below New Mexico through the Big Bend. It is not uncommon, particularly in areas near permanent water.
CHECKERED GARTER SNAKE
Thamnophis marcianus marcianus
The checkered garter snake is found throughout western 2/3 of the state. It is the most commonly seen of the garter snakes in the range of this work. As with many of the snakes, there is some variation in coloration throughout its range. Some books show them with a head the same color as the ground color, while this one has a dark head. This specimen is from Culberson County. Notice the yellow crescent marking behind the jaw, which is characteristic of the marcianus.