Checkered garter snake (Thamnophis marcianus)
The checkered garter snake is a snake in the family Colubridae with a mild venom for its prey, not dangerous to people. GBIF holds 2,644 licensed U.S. records of it; it reaches our listing threshold in 6 states, most of all Texas (1,851), Arizona (557) and New Mexico (126). Its observation records peak in July.
The checkered garter snake (Thamnophis marcianus) is a species of garter snake in the subfamily Natricinae of the family Colubridae. The species is native to the southwestern United States, Mexico, and Central America. There are two recognized subspecies.
From Wikipedia: Checkered garter snake, text under CC BY-SA 4.0.
Is the checkered garter snake poisonous or venomous?
Mildly venomous but not dangerous: the checkered 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 checkered garter snake?
The checkered garter snake's U.S. record is concentrated: Texas alone holds 70% of licensed records. It is listed in 6 states in all; the next are Arizona (557), New Mexico (126) and Oklahoma (68).
| # | State | Records | Share of state snakes | Rank in state |
|---|---|---|---|---|
| 1 | Texas | 1,851 | 4.5% | 6th of 86 |
| 2 | Arizona | 557 | 2.7% | 13th of 60 |
| 3 | New Mexico | 126 | 2.0% | 12th of 56 |
| 4 | Oklahoma | 68 | 0.5% | 38th of 50 |
| 5 | California | 21 | 0.0% | 43rd of 46 |
| 6 | Kansas | 19 | 0.1% | 41st of 44 |
When is the checkered garter snake seen?
Across the U.S., observation records of the checkered garter snake run mostly April through October, peaking in July with 20% of them. Winter (December to February) holds 3% of them.
Season by state
Among states whose main season falls within one calendar year, it starts earliest in March (Texas) and latest in June (Arizona). The most common peak month is July, shared by Arizona and Texas.
| State | Main season | Peak month | Observation records |
|---|---|---|---|
| Texas | March through October | July | 491 |
| Arizona | June through October | July | 33 |
Where the checkered garter snake is recorded in each state
Texas
Texas holds 1,851 licensed records, the 6th most recorded of 86 snakes listed there. Its observation records in Texas run mostly March through October, peaking in July; most licensed records come from Jeff Davis County, McMullen County and Frio County. Next come Bexar County (58) and Brewster County (57).
Arizona
Arizona holds 557 licensed records, the 13th most recorded of 60 snakes listed there. Its observation records in Arizona run mostly June through October, peaking in July; most licensed records come from Cochise County, Pima County and Maricopa County. Next come Pinal County (44) and Graham County (36).
New Mexico
New Mexico holds 126 licensed records, the 12th most recorded of 56 snakes listed there. Most of its licensed records in New Mexico come from Hidalgo County, Eddy County and Doña Ana County. Next come Quay County (9) and Grant County (8).
Oklahoma
Oklahoma holds 68 licensed records, the joint 38th most recorded of 50 snakes listed there. Most of its licensed records in Oklahoma come from Garfield County, Greer County and Jackson County. Next come Comanche County (6) and Kiowa County (6).
Top counties in the U.S.
| # | County | State | Records | Share of U.S. |
|---|---|---|---|---|
| 1 | Cochise County | Arizona | 222 | 8.4% |
| 2 | Jeff Davis County | Texas | 108 | 4.1% |
| 3 | Pima County | Arizona | 104 | 3.9% |
| 4 | Maricopa County | Arizona | 98 | 3.7% |
| 5 | McMullen County | Texas | 81 | 3.1% |
| 6 | Frio County | Texas | 59 | 2.2% |
| 7 | Bexar County | Texas | 58 | 2.2% |
| 8 | Brewster County | Texas | 57 | 2.2% |
| 9 | Travis County | Texas | 54 | 2.0% |
| 10 | Garza County | Texas | 47 | 1.8% |
| 11 | Pinal County | Arizona | 44 | 1.7% |
| 12 | Lubbock County | Texas | 39 | 1.5% |
| 13 | Medina County | Texas | 39 | 1.5% |
| 14 | Dickens County | Texas | 39 | 1.5% |
| 15 | Coke County | Texas | 38 | 1.4% |
How recent are the checkered garter snake records?
The checkered garter snake record leans on older material: only 16% of dated U.S. records come from 2017–2026, and the median record is from 1975. The oldest dated record is from 1852; the busiest year was 2016, with 132 records.
| Decade | Records | Share |
|---|---|---|
| 1850s | 3 | 0.1% |
| 1880s | 3 | 0.1% |
| 1890s | 17 | 0.7% |
| 1900s | 15 | 0.6% |
| 1910s | 61 | 2.5% |
| 1920s | 26 | 1.1% |
| 1930s | 130 | 5.4% |
| 1940s | 70 | 2.9% |
| 1950s | 311 | 13.0% |
| 1960s | 338 | 14.1% |
| 1970s | 302 | 12.6% |
| 1980s | 212 | 8.9% |
| 1990s | 134 | 5.6% |
| 2000s | 126 | 5.3% |
| 2010s | 348 | 14.5% |
| 2020s | 297 | 12.4% |
Species recorded in the same counties
Of the 41 counties where the checkered garter snake is most recorded, 37 are also top counties for the gopher snake, more than for any other snake. Venomous species among its neighbors: the western diamondback rattlesnake.
| Species | Shared counties |
|---|---|
| Gopher snake | 37 |
| Long-nosed snake | 27 |
| Glossy snake | 25 |
| Western diamondback rattlesnake venomous | 24 |
| Plains black-headed snake | 23 |
| Coachwhip | 22 |
| Chihuahuan night snake | 21 |
| Ring-necked snake | 21 |
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, Northwestern garter snake, Western aquatic garter snake, Plains garter snake and Eastern ribbonsnake.
GBIF records read 2026-09-29. Listed: any license. Counted: CC0/CC BY only. How we count.