Common Garter SnakeThamnophis sirtalisWhere and when to see them

The Common Garter Snake is a widespread North American snake found across much of the Columbia River region. It is strongly associated with moist habitats but also occupies grasslands, woodland edges, and other environments away from open water. Its striped body and active, ground-level hunting make it a characteristic reptile of riverside landscapes. By eating amphibians, invertebrates, and other small animals, it helps connect aquatic and terrestrial food webs. Although common overall, local populations can be affected by wetland loss, roads, and persecution.

Size

Usually 46–66 cm long; exceptionally large individuals can reach about 137 cm. Females generally grow larger than males.

Weight

Variable with length, sex, and body condition; adult females are generally heavier than males.

Lifespan

Often around 4–5 years in the wild; individuals can exceed 10 years in captivity.

Status

Least Concern

Common Garter Snakes are usually active during daylight, with activity shifting according to temperature and weather. They bask in sunny patches to warm their bodies and retreat beneath vegetation, logs, or stones when conditions become unsuitable. Capable swimmers, they may enter shallow water to hunt or escape danger. They locate prey using sight and chemical cues collected by their flicking tongues. In cold weather, they overwinter in protected underground refuges, sometimes sharing these sites with many other snakes. Mating commonly occurs after spring emergence, and females give birth to live young, usually in late summer. When threatened, a snake normally tries to flee, but if restrained it may release strong-smelling musk or bite.

• Females give birth to live young rather than laying eggs.
• A flicking tongue carries chemical samples to a sensory organ in the roof of the mouth.
• Some populations have evolved resistance to the potent toxins of newts they eat.
• Communal overwintering refuges may be used repeatedly across generations.

Wildlife opportunities depend on the river reach, water levels and species. River-specific viewing months have not been confirmed; general species seasons are not a local sighting forecast.

Along the Columbia River and its tributaries, suitable habitat includes marsh edges, wet meadows, vegetated banks, and floodplain woodland. Quiet backwaters, ponds, and side channels can provide both prey and nearby cover. These snakes also use drier grassland, open woodland, gardens, and disturbed ground where shelter is available. Dense vegetation, fallen wood, and rock crevices offer protection from predators and temperature extremes. Access to frost-protected overwintering refuges is especially important in colder parts of the watershed.

Common Garter Snakes eat a varied diet that often includes earthworms, frogs, toads, and salamanders. They also take fish, leeches, and other small animals when opportunities arise. Diet varies with locality, season, and the snake's size. Prey is generally seized and swallowed without constriction.

Common name

Common Garter Snake

Scientific name

Thamnophis sirtalis

Animal group

Reptiles

Size

Usually 46–66 cm long; exceptionally large individuals can reach about 137 cm. Females generally grow larger than males.

Weight

Variable with length, sex, and body condition; adult females are generally heavier than males.

Lifespan

Often around 4–5 years in the wild; individuals can exceed 10 years in captivity.

Status

Least Concern

Identification

Look for a slender snake with a long tail and usually three pale longitudinal stripes on a darker body. Stripe colors can be yellow, cream, blue, or greenish, and red markings may appear along the sides in Columbia River populations. Dark spots or checkering between the stripes are also common, but coloration varies considerably. Other garter snake species occur in the region, so stripes alone are not enough for a confident identification.