Black-necked Garter Snake

(Thamnophis cyrtopsis)

Color Photograph: Stephen P. Mackessy, U.S. Forest Service

Color Photograph: Jeff Servoss, U. S. Fish and Wildlife Service

Mexican Distribution not Shown

Black-necked Garter Snake (Thamnophis cyrtopsis)

Identification: Snake 16 to 42 inches in length. Dorsal stripe varying between white, yellow, or orange expanding slightly toward the neck and fading in color toward the tail. Lateral stripes white. Ground color between dorsal and lateral stripe gray-green to dark gray-brown. Lateral stripe occupies 2nd and 3rd scale rows. Neck with a large, conspicuous black blotch at the junction of the neck and head. Two alternating rows of vague, darker blotches between the dorsal and lateral stripes. Top of head gray-green, lower half white, with contrasting black streaks. Scales keeled and anal plate single.

Geographical Variation:

Western Blackneck Garter Snake (T. c. cyrtopsis): Alternating black blotches beween the dorsal and lateral stripes begin in the neck region. Range: Rest of the range of this species.

Eastern Blackneck Garter Snake (T. c. occelatus): Neck region between the dorsal and lateral stripes with a single large black spot. Range: Texas from the Edwards Plateau to the Big Bend Region.

Range (see map on left): The Blackneck Garter Snake is a species of the southwestern United States and Mexico. It ranges northward into Utah and Colorado, and southward through eastern Arizona, most of New Mexico, and eastward through western and south-central Texas. The distribution extends southward to central Mexico.

Habitat: Habitat choice is variable, but most individuals are found in mountains and high hills ranging from Spruce-Fir Forest to mesquite dominated desert. The Blackneck Garter Snake occurs in tropical forest further south in parts of Mexico. It is most commonly found along streams and the seepage areas of springs.

Food: Frogs, toads, and aquatic invertebrates.

Behavior: The Blackneck Garter Snake is a diurnal species and is commonly seen basking on rocks along streams. Sometimes seen swimming along the top of the water.

Reproduction:  This species is a live-bearing species and 8 to 10 young are born between June and August.

Black-necked Garter Snake
(Thamnophis cyrtopsis)

Similar Species:

Checkered Garter Snake (Thamnophis marcianus)

Mexican Garter Snake (Thamnophis eques)

Western Terrestrial Gartern Snake

(Thamnophis elegans)