[2] Subsequently, some authors have noted similarities between northern populations of the Mexican wandering garter snake and the southern subspecies of the western terrestrial garter snake (Thamnophis elegans vagrans), leading them to reclassify the former as another subspecies of the western terrestrial garter snake under the name Thamnophis elegans errans.

[2] However, a 280 km gap of uninhabitable low desert separates the ranges of the two populations.

[2] Additionally, even the closest populations of Mexican wandering and western terrestrial garter snakes are still morphologically separated by the number and arrangement of scales, as well as the color of the tongue.

[3] The Mexican wandering garter snake is endemic to Mexico, where it has been found in the states of Chihuahua, Durango, Jalisco, Nayarit, and Zacatecas.

[4][2] It has an extensive linear range in the pine-oak forests of the Sierra Madre Occidental.