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Blackneck Garter Snake

(Thamnophis cyrtopsis)


Identification: Top of head gray; white stripes on sides on second and third scale rows above outer edges of belly scales; yellowish stripe along middle of back; two large black blotches on neck; heavy black marks on vertical sutures between upper labial scales; upper scales keeled; anal scale single; maximum total length about 114 cm (45 inches) but seldom more than 75 cm (30 inches). The western terrestrial garter snake often is mistaken for this species.  

Colorado Distribution: Known to occur as far north as the Arkansas River valley in southeastern Colorado, in John Brown Canyon in Mesa County in west-central Colorado, and in southern La Plata and Archuleta counties in southwestern Colorado, at elevations below 6,500 feet. Spotty distribution, uncommon.    

View the distribution of observed Blackneck Garter Snake (Thamnophis cyrtopsis) on a map

Habitat: Vicinity of permanent and intermittent streams, often in canyon bottoms with rocky slopes covered in oak and/or juniper; frequently wanders away from streams, sometimes observed in open grassland, especially near dry washes or at temporary pools used by breeding toads. Takes shelters under rocks or wood, in crevices or burrows, or among exposed streamside tree roots.    

Life History: Limited information indicates that females give birth to their young in August. Forages on land and in shallow water on available larval and adult amphibians (especially anurans), small fishes, and tadpole shrimp.


Revised: July 24, 2003