Madrean Narrow-headed Garter Snake

Thamnophis unilabialis (Tanner, 1985)

Spanish Name Culebra de Agua de Cabeza-angosta
Max. Recorded Length 95.3 cm / 37.5 inches
Range Chihuahua, Coahuila, Durango, Sonora

Note: These species pages are in various stages of completion. Some are basically finished; others are very much under construction. Please be patient while I work on this section.

This species comprises the Mexican populations of garter snake that were previously assigned to the Narrow-headed Garter Snake, Thamnophis rufipunctatus. Most of what was known about that species before it was split appears to have been based on populations in Arizona and New Mexico; it is unclear how much is applicable to the Mexican populations that now make up this new species.

In 1985, Wilmer W. Tanner described Thamnophis rufipunctatus unilabialis as a new subspecies of the Narrow-headed Garter Snake. A decade later, Douglas Rossman considered the basis on which Tanner described this new subspecies insufficent for taxonomic recognition, and eliminated it as a distinct subspecies. In 2011, based on their genetic analysis, Wood et al. restored unilabialis and elevated it to full species status.

As it stands today, Thamnophis unilabialis is the middle member of a species complex that includes the Narrow-headed Garter Snake to its north and the Southern Durango Spotted Garter Snake, Thamnophis nigronuchalis, to its south. All three species can be characterized as long-nosed, brown or grey-brown spotted snakes that are found in aquatic habitat at high altitudes. Fish is their main prey item; amphibian larvae and tadpoles have also been reported.

Captive Care

Captive care is presumably similar to that of the Narrow-headed Garter Snake and other long-nosed aquatic garter snake species.

If you have experience with this species and would like to share, please contact me.

For general information on keeping garter snakes in captivity, please see the Care Guide.

Articles and News


Liner, Ernest A. 1994. Scientific and Common Names for the Amphibians and Reptiles of Mexico in English and Spanish. SSAR Herpetological Circular No. 23.

Rossman, Douglas A., Neil B. Ford and Richard A. Seigel. 1996. The Garter Snakes: Evolution and Ecology. Norman OK: University of Oklahoma Press.

Wood, Dustin A. et al. 2011. “Refugial isolation and divergence in the Narrowheaded Gartersnake species complex (Thamnophis rufipunctatus) as revealed by multilocus DNA sequence data.” Molecular Biology 20: 3856-3878.