The black-necked gartersnake, Thamnophis cyrtopsis, occurs from southeastern Utah and southern Colorado to Central America. Although the black-necked gartersnake is not exceedingly rare in Utah, it is the least common of Utah's three gartersnake species. It can be distinguished from Utah's other gartersnake species by the two large black blotches on the back of the head.
The black-necked gartersnake is almost always found near water. Accordingly, its major food items are amphibians and crustaceans. Females of the species give birth to between three and twenty-five live young each summer. The species is active from April to October, becoming inactive during the cold winter months.