Thamnophis elegans

Using mitochondrial data, Bronikowski and Arnold (2001) identified several clades within T. elegans that did not, in some cases, follow phenotypic subspecies boundaries. Hammerson (1999) found phenotypes assignable to T. e. arizonae and T. e. vascotanneri outside of their purported distributions within Colorado, and recommended that the two names be synonymized with T. e. vagrans. Hammerson's data supported similar action for Arizona and New Mexico populations as well (J. Boundy, pers. obs.). Thus, Crother (2017) tentatively retain three subspecies.

The range extends from central British Columbia, central Alberta, and southwestern Manitoba south through all of the western United States (east to western South Dakota, western Nebraska, Colorado, extreme western Oklahoma, and New Mexico) to (disjunctly) northern Baja California (Sierra San Pedro Martir), with many isolated populations around the margins of the main range (Fitch 1983, Rossman et al. 1996, Grismer 2002, Stebbins 2003). Elevational range extends from sea level to 11,000 feet (3,355 meters), or higher in some locations (Hammerson 1999, Stebbins 2003).

This species is represented by hundreds of occurrences or subpopulations (e.g., see maps in Fitch 1983, Degenhardt et al. 1996, and Hammerson 1999).

No major threats are known. In high-elevation areas of the southern Sierra Nevada in California, introductions of non-native trout apparently have led to declines in populations of amphibians and possibly also of T. elegans, which may depend on amphibians as a primary food resource (and which may occasionally serve as prey for trout) (Matthews et al. 2002). However, Matthews et al. (2002) did not discuss the historical distribution of T. elegans in their study areas, so the significance of extensive trout introductions in the absence of garter snakes from some areas (John Muir Wilderness) is uncertain. Further study is warranted (e.g., in the mountains of Colorado, T. elegans is a versatile feeder [Hammerson 1999], and garter snake populations may not rely strongly on amphibian populations).