Northwestern garter snake (Thamnophis ordinoides)
The northwestern garter snake is a snake in the family Colubridae with a mild venom for its prey, not dangerous to people. GBIF holds 3,930 licensed U.S. records of it; it reaches our listing threshold in 3 states, most of all Oregon (2,344), Washington (1,326) and California (223). Its observation records peak in May.
The northwestern garter snake (Thamnophis ordinoides) is a species of snake in the family Colubridae. The species is endemic to North America.
From Wikipedia: Northwestern garter snake, text under CC BY-SA 4.0.
Is the northwestern garter snake poisonous or venomous?
Mildly venomous but not dangerous: the northwestern garter snake has enlarged rear teeth and a mild venom for its prey, and a bite causes at most local swelling, which is why many sources simply call it harmless. It is not a pit viper or coral snake, the only U.S. land snakes with medically dangerous venom. Clean any bite like a small wound.
Which states have the northwestern garter snake?
The northwestern garter snake's U.S. record is concentrated: Oregon alone holds 60% of licensed records. It is listed in 3 states in all; the next are Washington (1,326) and California (223).
| # | State | Records | Share of state snakes | Rank in state |
|---|---|---|---|---|
| 1 | Oregon | 2,344 | 30.9% | 1st of 16 |
| 2 | Washington | 1,326 | 25.0% | 1st of 11 |
| 3 | California | 223 | 0.3% | 30th of 46 |
When is the northwestern garter snake seen?
Across the U.S., observation records of the northwestern garter snake run mostly March through October, peaking in May with 17% of them. Winter (December to February) holds 4% of them.
Season by state
Among states whose main season falls within one calendar year, it starts earliest in March (Oregon) and latest in April (Washington). Each of these states peaks in a different month: April in Oregon and May in Washington.
| State | Main season | Peak month | Observation records |
|---|---|---|---|
| Oregon | March through October | April | 507 |
| Washington | April through October | May | 321 |
Where the northwestern garter snake is recorded in each state
Oregon
Oregon holds 2,344 licensed records, the most recorded of 16 snakes listed there. Its observation records in Oregon run mostly March through October, peaking in April; most licensed records come from Tillamook County, Lincoln County and Clackamas County. Next come Curry County (208) and Multnomah County (181).
Washington
Washington holds 1,326 licensed records, the most recorded of 11 snakes listed there. Its observation records in Washington run mostly April through October, peaking in May; most licensed records come from San Juan County, King County and Kitsap County. Next come Pierce County (111) and Lewis County (95).
California
California holds 223 licensed records, the 30th most recorded of 46 snakes listed there. Most of its licensed records in California come from Del Norte County, Siskiyou County and Humboldt County. Next come Alameda County (4) and Mendocino County (2).
Top counties in the U.S.
| # | County | State | Records | Share of U.S. |
|---|---|---|---|---|
| 1 | Tillamook County | Oregon | 503 | 12.8% |
| 2 | Lincoln County | Oregon | 328 | 8.3% |
| 3 | Clackamas County | Oregon | 214 | 5.4% |
| 4 | Curry County | Oregon | 208 | 5.3% |
| 5 | Del Norte County | California | 197 | 5.0% |
| 6 | Multnomah County | Oregon | 181 | 4.6% |
| 7 | San Juan County | Washington | 155 | 3.9% |
| 8 | Lane County | Oregon | 150 | 3.8% |
| 9 | King County | Washington | 150 | 3.8% |
| 10 | Yamhill County | Oregon | 139 | 3.5% |
| 11 | Columbia County | Oregon | 132 | 3.4% |
| 12 | Kitsap County | Washington | 123 | 3.1% |
| 13 | Pierce County | Washington | 111 | 2.8% |
| 14 | Coos County | Oregon | 98 | 2.5% |
| 15 | Lewis County | Washington | 95 | 2.4% |
How recent are the northwestern garter snake records?
The northwestern garter snake record leans on older material: only 20% of dated U.S. records come from 2017–2026, and the median record is from 1978. The oldest dated record is from 1889; the busiest year was 2000, with 250 records.
| Decade | Records | Share |
|---|---|---|
| 1880s | 14 | 0.4% |
| 1890s | 62 | 1.6% |
| 1900s | 44 | 1.1% |
| 1910s | 220 | 5.6% |
| 1920s | 84 | 2.1% |
| 1930s | 649 | 16.5% |
| 1940s | 511 | 13.0% |
| 1950s | 120 | 3.1% |
| 1960s | 107 | 2.7% |
| 1970s | 154 | 3.9% |
| 1980s | 121 | 3.1% |
| 1990s | 102 | 2.6% |
| 2000s | 815 | 20.8% |
| 2010s | 252 | 6.4% |
| 2020s | 669 | 17.0% |
Species recorded in the same counties
Of the 39 counties where the northwestern garter snake is most recorded, 31 are also top counties for the common garter snake, more than for any other snake. None of its closest neighbors is venomous.
| Species | Shared counties |
|---|---|
| Common garter snake | 31 |
| Northern rubber boa | 17 |
| Western terrestrial garter snake | 17 |
| Gopher snake | 13 |
| Eastern racer | 12 |
| Ring-necked snake | 11 |
| Aquatic garter snake | 9 |
| California kingsnake | 9 |
Related species in the U.S.
Other species of the genus Thamnophis with profiles here: Western terrestrial garter snake, Common garter snake, Western ribbon snake, Aquatic garter snake, Western aquatic garter snake, Plains garter snake, Checkered garter snake and Eastern ribbonsnake.
GBIF records read 2026-09-29. Listed: any license. Counted: CC0/CC BY only. How we count.