Common garter snake (Thamnophis sirtalis)

Mildly venomous but not dangerous: the common 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.

Records are spread over 47 states; the top three, California, New York and Oregon, hold 35% of them. It is the most recorded snake of all in New York, Michigan, Pennsylvania, Ohio, Massachusetts, Maine, Wisconsin, Vermont, Minnesota, Illinois, New Hampshire, Connecticut, New Jersey, Kentucky and Rhode Island.

Across the U.S., observation records of the common garter snake run mostly March through October, peaking in May with 18% of them. Winter (December to February) holds 3% of them.

Observation records run through most of the year in Florida and Oregon. Among states whose main season falls within one calendar year, it starts earliest in February (Georgia, Louisiana and Tennessee) and latest in May (Idaho, Maine, Montana, New Hampshire and West Virginia). The most common peak month is May, shared by Alabama, Connecticut, Delaware, Georgia, Illinois, Indiana and 7 more.

California holds 5,777 licensed records, the 3rd most recorded of 46 snakes listed there. Its observation records in California run mostly March through November, peaking in April; most licensed records come from Shasta County, Lassen County and San Mateo County. Next come Humboldt County (409) and Siskiyou County (306).

New York holds 2,347 licensed records, the most recorded of 17 snakes listed there. Its observation records in New York run mostly April through October, peaking in April; most licensed records come from Ulster County, Tompkins County and Onondaga County. Next come Broome County (148) and Monroe County (98).

Oregon holds 1,935 licensed records, the 2nd most recorded of 16 snakes listed there. Its observation records in Oregon run through most of the year, peaking in March; most licensed records come from Yamhill County, Columbia County and Lincoln County. Next come Lane County (122) and Klamath County (117).

Michigan holds 1,840 licensed records, the most recorded of 17 snakes listed there. Its observation records in Michigan run mostly April through October, peaking in April; most licensed records come from Washtenaw County, Isabella County and Wayne County. Next come Oakland County (76) and Cheboygan County (65).

Pennsylvania holds 1,686 licensed records, the most recorded of 20 snakes listed there. Its observation records in Pennsylvania run mostly March through October, peaking in May; most licensed records come from Allegheny County, Erie County and Westmoreland County. Next come Crawford County (64) and Philadelphia County (61).

Ohio holds 1,624 licensed records, the most recorded of 25 snakes listed there. Its observation records in Ohio run mostly March through September, peaking in May; most licensed records come from Summit County, Cuyahoga County and Portage County. Next come Erie County (78) and Lucas County (76).

North Carolina holds 1,325 licensed records, the 3rd most recorded of 39 snakes listed there. Its observation records in North Carolina run mostly March through October, peaking in April; most licensed records come from Wake County, Macon County and Watauga County. Next come Graham County (61) and New Hanover County (53).

Washington holds 1,269 licensed records, the 2nd most recorded of 11 snakes listed there. Its observation records in Washington run mostly April through October, peaking in July; most licensed records come from Thurston County, Pierce County and Jefferson County. Next come King County (102) and Clallam County (102).

Virginia holds 1,057 licensed records, the 3rd most recorded of 30 snakes listed there. Its observation records in Virginia run mostly March through October, peaking in April; most licensed records come from Fairfax County, Highland County and Chesapeake. Next come Giles County (44) and Bath County (40).

Massachusetts holds 1,035 licensed records, the most recorded of 13 snakes listed there. Its observation records in Massachusetts run mostly April through October, peaking in May; most licensed records come from Middlesex County, Worcester County and Essex County. Next come Norfolk County (106) and Plymouth County (62).

Kansas holds 651 licensed records, the 5th most recorded of 44 snakes listed there. Its observation records in Kansas run mostly March through October, peaking in April; most licensed records come from Douglas County, Johnson County and Leavenworth County. Next come Russell County (23) and Linn County (22).

Florida holds 547 licensed records, the 6th most recorded of 49 snakes listed there. Its observation records in Florida run through most of the year, peaking in March; most licensed records come from Miami-Dade County, Martin County and Highlands County. Next come Alachua County (30) and Osceola County (28).

Maryland holds 492 licensed records, the 3rd most recorded of 20 snakes listed there. Its observation records in Maryland run mostly March through October, peaking in April; most licensed records come from Montgomery County, Prince George's County and Baltimore County. Next come Garrett County (51) and Frederick County (46).

Maine holds 471 licensed records, the most recorded of 9 snakes listed there. Its observation records in Maine run mostly May through October, peaking in August; most licensed records come from Hancock County, Franklin County and Penobscot County. Next come Cumberland County (39) and Piscataquis County (38).

Wisconsin holds 469 licensed records, the most recorded of 16 snakes listed there. Its observation records in Wisconsin run mostly April through October, peaking in May; most licensed records come from Winnebago County, Juneau County and Dane County. Next come Vilas County (29) and Dodge County (24).

Vermont holds 462 licensed records, the most recorded of 9 snakes listed there. Its observation records in Vermont run mostly April through October, peaking in May; most licensed records come from Chittenden County, Washington County and Windham County. Next come Windsor County (42) and Rutland County (40).

Minnesota holds 428 licensed records, the most recorded of 15 snakes listed there. Its observation records in Minnesota run mostly April through October, peaking in May; most licensed records come from Hennepin County, Lake County and St. Louis County. Next come Cook County (21) and Anoka County (18).

Illinois holds 427 licensed records, the most recorded of 33 snakes listed there. Its observation records in Illinois run mostly March through September, peaking in May; most licensed records come from Lake County, Cook County and DuPage County. Next come Will County (26) and Richland County (23).

Nebraska holds 326 licensed records, the 2nd most recorded of 31 snakes listed there. Its observation records in Nebraska run mostly April through October, peaking in October; most licensed records come from Keith County, Gage County and Cherry County. Next come Pawnee County (22) and Nance County (14).

New Hampshire holds 325 licensed records, the most recorded of 9 snakes listed there. Its observation records in New Hampshire run mostly May through October, peaking in June; most licensed records come from Cheshire County, Hillsborough County and Grafton County. Next come Rockingham County (48) and Sullivan County (32).

Connecticut holds 310 licensed records, the most recorded of 14 snakes listed there. Its observation records in Connecticut run mostly April through October, peaking in May; most licensed records come from New Haven County, Litchfield County and Hartford County. Next come Fairfield County (40) and New London County (24).

New Jersey holds 292 licensed records, the most recorded of 18 snakes listed there. Its observation records in New Jersey run mostly March through October, peaking in April; most licensed records come from Middlesex County, Morris County and Bergen County. Next come Mercer County (20) and Sussex County (19).

Indiana holds 287 licensed records, the 2nd most recorded of 27 snakes listed there. Its observation records in Indiana run mostly March through September, peaking in May; most licensed records come from Monroe County, Morgan County and Porter County. Next come Marshall County (14) and Marion County (13).

South Dakota holds 271 licensed records, the 4th most recorded of 16 snakes listed there. Most of its licensed records in South Dakota come from Bon Homme County, Clay County and Roberts County. Next come Custer County (24) and Union County (24).

Oklahoma holds 269 licensed records, the 18th most recorded of 50 snakes listed there. Most of its licensed records in Oklahoma come from Cleveland County, Johnston County and Payne County. Next come McClain County (13) and Cherokee County (11).

The common garter snake record leans on older material: only 40% of dated U.S. records come from 2017–2026, and the median record is from 2001. The oldest dated record is from 1848; the busiest year was 2025, with 1,783 records.

Of the 606 counties where the common garter snake is most recorded, 258 are also top counties for the eastern racer, more than for any other snake. Venomous species among its neighbors: the eastern copperhead.

Other species of the genus Thamnophis with profiles here: Western terrestrial garter snake, Western ribbon snake, Aquatic garter snake, Northwestern garter snake, Western aquatic garter snake, Plains garter snake, Checkered garter snake and Eastern ribbonsnake.