Gartersnake
(Thamnophis spp.)

Order: Squamata
Family: Colubridae (colubrid snakes)
Spanish name: culebra de agua

Distinguishing Features

Gartersnakes in the Sonoran Desert region are slender with a maximum length of 3¼ feet (106 cm). Most species have light-colored stripes on the top and sides of an otherwise olive-green or dark body. There are many different kinds of gartersnakes, but only two will be discussed here. They are the black-necked gartersnake (Thamnophis cyrtopsis) and the checkered gartersnake (Thamnophis marcianus). They can be distinguished from each other by the position of the side stripe: this stripe is confined to the second and third scale rows on T. cyrtopsis and the third scale row on T. marcianus. Also the black-necked gartersnake has 2 large black blotches behind the head, while the checkered gartersnake has large, squarish, dark blotches in a checkered pattern on its body.

Checkered gartersnake

Range

Both species are found throughout the Sonoran Desert. Additionally, T. cyrtopsis ranges from southeastern Utah to Guatamala and from central Texas to central and southern Arizona. Isolated populations occur in the Hualapai Mountains, Burro Creek, and Ajo mountains in western Arizona. T. marcianus is found in southwestern Kansas south to Zacatecas and northern Veracruz, Mexico, and from east-central Texas to south central Arizona and east-central Sonora, Mexico. A disjunct population occurs around the juncture of California, Arizona, northern Baja California, and Sonora, Mexico.

Habitat

Both species are semi-aquatic, generally found in or near bodies of water ranging from streams to canals, ponds, and cattle tanks. The black-necked gartersnake is found from desert through mixed conifer forest, as well as tropical habitats in Mexico. The checkered gartersnake usually inhabits lowland river systems, ponds, springs, streams, rivers, and irrigation ditches in arid and semiarid regions. Occasionally it is found in oak-pine woodlands.

Life History

Both species feed on aquatic or semi-aquatic prey, including fish, frogs, toads, tadpoles, worms, salamanders, and crustaceans. Lizards, small mammals, and birds may also be eaten. Gartersnakes are live-bearers, generally giving birth to 6 to 18 young in the summer. If disturbed, gartersnakes will bite, defecate, and emit foul-smelling musk to deter the intruder.

Comments

Gartersnake habitat is disappearing throughout the Sonoran Desert due to habitat destruction and fragmentation. Gartersnake numbers have also declined due to competition with and predation by introduced species such as bullfrogs and sunfish. These introduced animals eat small snakes as well as the fishes and tadpoles which are food for gartersnakes.