Pacific Northwest Garter Snakes

Three of these numbers are ranges rather than settled figures. First, gestation length is documented for Northwestern gartersnake at roughly nine weeks, but no published source gives a gestation figure for the Puget Sound, Valley, or Red-spotted subspecies individually. Oregon State University Extension simply reports common gartersnake young arriving July through September without stating how long the female carried them. Second, birth timing for Northwestern gartersnake is given as late August by the academic source and as July through September by a broader account, which agree on the season and differ on the peak. Third, litter size is not one number: 5 to 9 for Northwestern gartersnake against 3 to 80 for common gartersnake, a spread driven mostly by female size. Lifespan carries the same spread the whole genus does, with common gartersnake documented to 10 years in captivity by Oregon's extension account and the National Park Service describing a considerably wider wild-versus-captive gap.

None of the four is venomous

None of these four snakes is venomous in any medically meaningful sense, and that is the first thing to settle. Washington's Department of Fish and Wildlife states that of all the snakes in Washington, only the Western rattlesnake is capable of inflicting a venomous bite. A rattlesnake is separated from all four by its rattle and its heavy, thick body, and it is not a striped snake. If you are looking at a slender striped or spotted snake in a Pacific Northwest yard, you are looking at a harmless animal, and the only question left is what to call it.

Step one: look at the head

Step one: is it a Northwestern gartersnake or a common gartersnake? Look at the head. This is the tell that works in the field and it needs no measuring. Northwestern gartersnake has a relatively small head with small eyes. Common gartersnake, per Animal Diversity Web, has a larger, longer head with bigger eyes. The size difference backs it up: Northwestern gartersnake is the smallest of Washington's gartersnakes according to the Burke Museum, with most adults between 12 and 24 inches, while a common gartersnake in the same yard is often noticeably longer and thicker through the body.

Step two: geography does half

Step two, and geography does half the work here. If it is a common gartersnake, where you are standing narrows which subspecies it is before you look at a single scale. Washington's Department of Fish and Wildlife assigns each of the three a distinct part of the state: Puget Sound gartersnake in the Puget Trough lowlands, Red-spotted gartersnake along the Pacific Coast and the southern Puget Trough, and Valley gartersnake in eastern Washington. In Oregon, the Red-spotted form is the Willamette Valley snake and the Valley gartersnake is the broader statewide one. Start with your own location, then check color against the subspecies you would expect to have.

Puget Sound: turquoise stripes

Puget Sound gartersnake: black base, and stripes that can be turquoise. The Burke Museum describes it as slender and black, with turquoise or black bellies and bright yellow or turquoise stripes. Occasional vertical red flecks show along the sides. A slim black snake with blue or turquoise striping in the Puget lowlands is not a mystery animal, it is this one.

Valley: one tidy row of red

Valley gartersnake: red kept in a single tidy row, and thick yellow stripes. The practical tell is where the red sits rather than whether red is present at all. On a Valley gartersnake the red coloring is usually confined to the area just above the lateral stripes, in a single row, against a dark gray, black, or brown ground color, and the head stays dark without extensive red. The Burke Museum describes it as showing more pronounced red side blotches and thicker yellow dorsal and lateral stripes than the Puget Sound form, often with red bellies. Washington's own agency notes that eastern Washington individuals, which is where this subspecies lives, show black bodies with bright yellow stripes and distinct red side blotches.

Red-spotted: red along the sides

Red-spotted gartersnake: red everywhere along the sides, not in one row. This is the vivid one, and it is the easiest of the three to call once you have seen it. The body is deep black with extensive, brilliant red lateral spotting and a bright yellow, orange, or cream stripe down the center of the back. The head is black with faint red or orange highlights, and the underside is often blue-gray or checkered. It is widely regarded as one of the most vividly colored subspecies of the common gartersnake anywhere in its range. If the red is bold and spread across the sides rather than lined up in a single row above the side stripe, you are looking at Red-spotted rather than Valley.

Do not lean on color here

Color is a weak tell for Northwestern gartersnake specifically, so do not lean on it. This species is the variable one. Its dorsal stripe can be red, orange, gold, yellow, greenish, blue, white, or tan, and it can also be narrow, dull, or effectively absent. The ground color underneath runs blackish, olive, brownish, bluish, or gray, often with reddish tints, and the belly ranges yellowish through brown, gray, or black, sometimes with dark spots or red flecks. Trying to match a Northwestern gartersnake to a photograph by color will fail more often than it works. Match head size first.

For certainty, count scales

If you have a clear photo and want certainty, count scales. This is the objective version of the same question, and it is the tell Washington's Department of Fish and Wildlife uses itself. Northwestern gartersnake carries 17 mid-body scale rows, occasionally 19, with 7 upper-lip scales and 8 to 9 lower-lip scales. Common gartersnake carries 19 mid-body scale rows, with 7 upper-lip scales and 10 lower-lip scales. The lower-lip count, 8 or 9 against 10, is the cleanest single number in the comparison. This is a photo exercise, not a reason to pick a snake up.

Two more garters share this ground

Western terrestrial gartersnake and western aquatic gartersnake are separate species also found in Oregon and Washington, which is why Oregon State University Extension counts four kinds of garter snake in that state and says plainly that they look very much alike and often live together in the same area. Oregon's four is a slightly different set of four. One field tell is worth carrying anyway: on a Northwestern gartersnake, the dark dorsal spots do not invade the stripe running down the center of the back, while on a western terrestrial gartersnake the upper spots do invade it.

No damage to look for

There is no damage to look for, because none of these snakes causes any. No gnawing, no chewed wiring, no burrowing into a foundation, no droppings pattern, no entry hole. None of the four enters wall voids or living space. The sign is the snake, and the only useful question is which one it was.

The sighting, and where it happens

The visual sighting, and the two places it tends to happen. A striped or red-spotted snake basking on rocks, pavement, or bare warm soil near cover, or moving through grass, garden beds, pond edges, or damp shaded ground. Where it happens is itself a clue. Common gartersnake favors sites in or near water, while Northwestern gartersnake is more often found well away from open water in vegetated cover, frequently under a board or a piece of flat debris.

Nothing to hear

These snakes are silent. No rattle, no buzzing, no scratching inside a wall. If you are hearing something in a structure, this animal is not the cause. Look at rodents or other wildlife instead.

A smell means someone got close

There is a real smell sign, and it means somebody already got too close. Handled, cornered, or nosed by a dog, both species smear a foul-smelling musk from glands near the tail. Oregon State University Extension describes the odor as much like a skunk. A sudden sharp musky smell after a pet went into the mulch is a strong tell that a garter snake was right there. The musk is unpleasant and completely harmless.

A cluster means a season

A cluster of sightings usually means a season, not a population change. Several snakes in one corner of a property in early spring or in fall commonly points to a shared overwintering den nearby or to one of the two breeding windows, and a run of small snakes in late summer is simply one female's litter dispersing. Neither is an infestation, and neither calls for a response.

Leave the snake alone

The default recommendation from every source is to leave the snake alone. Both species earn their keep. Northwestern gartersnake specializes heavily in slugs, particularly banana slugs, and in earthworms, with the occasional snail or small amphibian. Common gartersnake takes a much broader menu including frogs, toads, salamanders, fish, slugs, earthworms, leeches, insects, small mammals, and birds. On a Pacific Northwest property, a garter snake is a slug control program that showed up on its own. The realistic goal for a homeowner who is uncomfortable is fewer encounters, not removal.

Take away the cover first

If you want fewer sightings, take away the cover first. Washington's Department of Fish and Wildlife recommends removing rock piles, woodpiles, and unmowed tall grass immediately next to the house. Flat boards, scattered debris, and heavy ground-level cover along foundations and walkways are exactly the microhabitats these snakes shelter in, and clearing them does more to reduce how often you cross paths with one than anything else on this list.

Cut the food supply

The target is the prey, not the snake. Securing birdseed and other rodent attractants matters here for an indirect reason: reducing the prey base near a structure removes the reason a snake lingers there. This is the same guidance Washington's own agency gives, and it is a food-source fix rather than a snake fix.

Seal the ground-level gaps

Seal ground-level gaps so a snake cannot tuck in against the building. Washington's Department of Fish and Wildlife recommends closing cracks and holes in foundations and exterior walls with quarter-inch mesh hardware cloth, caulk, or concrete patching, and installing metal flashing under garage doors with tight weather-stripping as an added barrier. Set expectations correctly: this is about keeping a snake from sheltering against the structure, not about keeping one out of your living space, because these snakes do not go there.

Survey before you mow

Wet ground and sunny forest edges are where it matters. This is a specific piece of Washington guidance, and it is the one prevention step that protects the snake as much as the homeowner. Where tall grass adjoins a wet area or a sunny forest edge known to hold snakes, the agency's recommendation is to leave it unmowed. If mowing is necessary, walk the area first and move or direct any snakes to safety before you cut.

The bite and the musk, honestly

The bite and the musk, stated honestly rather than softened. These snakes rarely bite and flee first, but a handled or cornered one may strike and will musk. Washington's Department of Fish and Wildlife states that only the Western rattlesnake is capable of a venomous bite among Washington's snakes and treats a non-venomous snake bite as essentially harmless, cleaned and watched like a minor cut. One honest footnote belongs alongside that: Oregon State University Extension states that garter snake saliva seems to be toxic to amphibians and other small animals and can produce swelling in some people. That is real, and it is minor. It means a bite is not literally zero-effect, not that these snakes are venomous. There are no fangs and no delivery system behind it, any reaction is localized and short-lived, and the whole scenario requires you to have picked the animal up. Do not, and none of this applies.

Washington regulates handling

Washington law regulates handling any snake, and this is worth knowing before you move one. Per Washington's Department of Fish and Wildlife, it is unlawful to import into the state, hold, possess, offer for sale, sell, or release any snake species into the wild without the proper license. That is a general wildlife-handling rule covering all snakes in Washington, native and non-native alike. It is not a special protection attached to these four taxa, and none of them is listed as threatened, endangered, or otherwise specially protected in Washington or Oregon. Neither state publishes a trapping season, bag limit, reporting requirement, or possession permit specific to these snakes. State rules do vary and they do change, so verify the current rule where you live before any hands-on removal.

When to Call a Wildlife Control Operator

Most encounters need no professional response at all, and doing nothing is a completely reasonable choice here. Call when the answer is uncertainty rather than danger: if you cannot confidently tell whether the snake in front of you is one of these harmless species or Washington's one venomous species, do not handle it, and get an identification from a wildlife control professional or your state wildlife agency. Washington's Department of Fish and Wildlife also advises that if a snake gets into the house and you are not comfortable removing it yourself, contact a wildlife control company or your local Fish and Wildlife office for a referral. A licensed operator is the safer default over a do-it-yourself capture, both because handling and release are regulated in Washington and because the identification question gets answered by someone qualified to answer it.