Thamnophis marcianus, commonly known as the Checkered Garter Snake, is found in grassy fields and wetlands of the southwestern United States and Mexico. It exhibits a distinctive checkerboard pattern of green and black squares along its back. This non-venomous snake is diurnal, feeding on amphibians and small fish.

Thamnophis marcianus, commonly known as the Checkered Gartersnake, is native to North America. It is primarily found in the southwestern United States, particularly in states such as Texas, New Mexico, and Arizona. Its range extends into northern Mexico, including regions such as Chihuahua, Coahuila, and Tamaulipas.

The Checkered Gartersnake typically inhabits a variety of environments. It is often found in semi-arid regions, preferring areas near water sources such as streams, ponds, and rivers. These environments provide the necessary humidity and prey availability. The climate in these regions can vary, but it generally includes hot summers and mild winters.

As a semi-aquatic snake, Thamnophis marcianus occupies a niche where it can exploit both terrestrial and aquatic prey. It feeds primarily on amphibians, fish, and small invertebrates. The snake's ability to thrive in diverse environments such as grasslands, deserts, and riparian zones demonstrates its adaptability. Variations in habitat can occur due to regional adaptations, where some populations may be more terrestrial or aquatic depending on local conditions.