Thamnophis proximus, commonly known as the western ribbon snake or western ribbonsnake, is a species of garter snake in the subfamily Natricinae of the family Colubridae. The species is found in the central and southern United States, Mexico, and Central America south to central Costa Rica. The species has six recognized subspecies.

Description

T. proximus is a slender snake with a very long tail, approximately one-third of the total length of the body. Dorsally, T. proximus is blackish, brown, or olive with three light-colored stripes. Ventrally, it is greenish-white or yellowish-white. The upper labials are whitish and unmarked, contrasting with the dark top and sides of the head. The specific name, proximus, describes the species' similarity to T. saurita. Adults measure 17 – in total length (including the tail).

Subspecies

Six subspecies of the western ribbon snake (T. proximus) are recognized as being valid, including the nominate subspecies. Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Thamnophis.

Ecology

T. proximus is a semiaquatic snake that occurs in a wide range of habitats, usually not far from water. It can be found from sea level to nearly 2500 m. It feeds on a range of invertebrates (earthworms, crayfish) and small vertebrates (lizards, fishes, and frogs, including tadpoles).