Common Garter Snake
Thamnophis sirtalis • Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Widely distributed throughout North America, including most of the United States (except the desert Southwest), southern Canada, and parts of Mexico.
Look up Common Garter Snake in the Snake Encyclopedia →Venomous Status
Technically mildly venomous (opisthoglyphous/rear-fanged) but functionally non-venomous to humans.
Danger Level
Harmless / Low Risk. Bites may cause minor localized swelling or itching but do not pose a serious threat to healthy adults.
Family
Order: Squamata, Suborder: Serpentes, Family: Colubridae, Subfamily: Natricinae, Genus: Thamnophis, Species: Thamnophis sirtalis
Conservation
IUCN Red List: Least Concern. They are adaptable and face few major threats, though habitat loss and pesticides can affect local populations.
Physical Description
Variable coloration but typically features three longitudinal stripes (one dorsal, two lateral) on a dark background. This specimen shows a checkerboard pattern of dark spots between the stripes. Head is slightly wider than the neck, with large eyes and round pupils. Scales are keeled (ridged).
Size & Dimensions
The specimen in the image appears to be an adult, approximately 20-30 inches (50-76 cm) in length. Species typically ranges from 18 to 54 inches.
Habitat
Generalist species found in forests, grasslands, fields, and suburban gardens. They are almost always found near water sources such as ponds, streams, or marshes. Occurs from sea level to high elevations.
Behavior & Temperament
Diurnal and active forager. Generally timid and will flee if approached. If cornered, it may flatten its head, strike defensively, or release a foul-smelling musk from its cloaca.
Diet & Feeding
Diet consists of earthworms, slugs, frogs, toads, salamanders, fish, and occasionally small mammals or birds. They hunt through active foraging and rely on scent and sight.
Reproduction
Ovoviviparous (gives birth to live young). Litters are typically large, ranging from 10 to 40 young, born in late summer or early autumn.
Venom Profile
The saliva contains mild toxins that are effective on small prey like amphibians, but it is not medically significant to humans.
Look-alikes
Commonly confused with Ribbon Snakes (Thamnophis saurita), which are more slender and have the lateral stripes on the 3rd and 4th scale rows, and various species of DeKay's Brownsnakes.
Conservation Status
IUCN Red List: Least Concern. They are adaptable and face few major threats, though habitat loss and pesticides can affect local populations.
Cultural Significance
One of the most commonly encountered snakes in North America, often serving as an introductory species for budding naturalists. They play a vital ecological role in controlling pest populations like slugs.
Notable Features
Highly tolerant of cold temperatures; they are often the first snakes to emerge in spring and last to enter brumation in fall. Some populations in the Pacific Northwest have evolved resistance to the toxins found in Pacific Newts.