Checkered Garter Snake
Thamnophis marcianus • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: T. marcianus
Found primarily in the Southwestern United States (Texas, New Mexico, Arizona, Oklahoma, Kansas), Mexico, and as far south as Central America (Guatemala, Belize, Nicaragua).
Look up Checkered Garter Snake in the Snake Encyclopedia →Venomous Status
Non-venomous (though members of the genus possess a Duvernoy's gland that produces mild saliva, they lack a delivery system and are harmless to humans).
Danger Level
Harmless - poses no threat to humans or pets; very low risk of bite and no significant toxicity.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: T. marcianus
Conservation
Least Concern (IUCN) as the species is widespread and adaptable to human-altered landscapes.
Physical Description
Distinctive checkerboard pattern of black squares on a greenish-tan or yellowish ground color. Features three light-colored longitudinal stripes: one down the center of the back and one on each side. The head is relatively narrow with large eyes and round pupils. Scales are heavily keeled.
Size & Dimensions
The specimen in the image appears to be a juvenile, likely under 30 cm. Adults typically range from 45 to 100 cm in length.
Habitat
Generalist species often found near water sources like ponds, streams, and irrigation ditches, but also inhabits arid grasslands and scrublands from sea level to approximately 2,200 meters elevation.
Behavior & Temperament
Diurnal and active forager. When threatened, they may flatten their heads to appear larger, strike defensively (rarely biting), or release a foul-smelling musk from their cloaca. Generally timid and quick to flee.
Diet & Feeding
Active hunter with a varied diet including earthworms, slugs, frogs, toads, tadpoles, small fish, and occasionally small lizards or rodents.
Reproduction
Viviparous (gives birth to live young). Litter sizes typically range from 6 to 30 young, usually born between June and August.
Venom Profile
Non-venomous - no medically significant venom.
Look-alikes
Commonly confused with other garter snakes like the Western Ribbon Snake (Thamnophis proximus) or the Black-necked Garter Snake (Thamnophis cyrtopsis), but distinguished by the specific checkerboard spacing and location of the lateral stripes.
Conservation Status
Least Concern (IUCN) as the species is widespread and adaptable to human-altered landscapes.
Cultural Significance
Functionally important in ecosystems for controlling populations of amphibians and invertebrates; frequently kept as pets due to their manageable size and color variations (such as albino strains).
Notable Features
Adaptability to arid environments compared to other semi-aquatic garter snakes; the specific placement of the lateral stripes on the 2nd and 3rd scale rows is a diagnostic feature for the species.