This medium-sized snake is usually no longer than 42” long. Like other garter snakes, it is a slender dark olive-gray snake with stripes along its back and sides. It has a single orange-yellow mid-dorsal stripe (a stripe down the middle of its back) that starts out brilliant orange at the head and grades to a lighter yellow towards the end of the tail. Another cream or white stripe runs along each lower side of the snake's body. Two distinctive jet-black blots mark the snake right behind the head and are key to identifying this snake. The top of the head is usually plain gray or blue-gray in color, and the underside of the snake is somewhere between a pale gray and a cream color. Dark bars mark the seams of the upper lip scales (upper labials). The pupils are round and the dorsal scales are keeled.
The black-necked garter snake can be found throughout the Sonoran Desert and has a range extending from southeastern Utah down through central Texas and southern Arizona to Guatemala. Isolated populations exist in the Hualapai Mountains, Burro Creek, and Ajo Mountains in western Arizona. It ranges in elevation from around 1000 ft to 7000 ft.
Diet and Behavior
The black-necked garter snake is a semi-aquatic snake and primarily a diurnal and crepuscular (twilight-loving) snake. However, it can sometimes be found active on warm nights. It can usually be found during the mid-morning or late afternoon hunting for tadpoles, frogs, toads, lizards, salamanders, earthworms, and invertebrates. In captivity, the snake will sometimes eat fish as well. This snake is usually found near water, though it sometimes wanders far from water. It hibernates during the colder months of fall and winter. In the late spring or summer, the snake gives birth to up to 25 young.
Although the black-necked garter snake is not considered venomous, it does have some defenses. When disturbed, this snake gives off a musky odor, and their bite can swell and cause redness and irritation in some people.
There are three recognized subspecies: the Tropical Black-necked Garter Snake, the Western Black-necked Garter Snake, and the Eastern Black-necked Garter Snake. The Tropical Black-necked Garter snake, Thamnophis cyrtopsis collaris, primarily inhabits a range in southwestern and southern Mexico; Guatemala. The Western Black-necked Garter Snake, Thamnophis cyrtopsis cyrtopsis, is found primarily in West Texas, the western U.S., and north-central Mexico. The Eastern Black-necked Garter Snake, Thamnophis cyrtopsis ocellatus, is a brilliantly colored subspecies native to Central Texas.