Venomous snakes and spiders in Wisconsin

Wisconsin's venomous snakes are two rattlesnake species. Together they account for 58 licensed records; the timber rattlesnake alone has 79% of them, and the least recorded, the eastern massasauga, has 12.

One widow species (Northern black widow: 1 record) is on the Wisconsin list. There is no recluse spider on the Wisconsin list: no recluse species reaches 10 records in the state. Widow bites cause muscle pain and cramps; recluse bites can cause a slow-healing wound. Both are rare and seldom fatal.

These eight account for 85% of all licensed snake records in Wisconsin; the most recorded, the common garter snake, alone for 48%.

These eight account for 20% of all licensed spider records in Wisconsin; the most recorded, the zebra spider, alone for 4%.

Observation records of snakes in Wisconsin run mostly April through October, peaking in May with 20% of them. December through February together hold under 2% of the records, so snakes in Wisconsin are rarely recorded in winter. Venomous snakes alone have three observation records with a month in Wisconsin, too few for a season of their own.

Observation records of spiders in Wisconsin run mostly May through October, peaking in August with 23% of them. Winter (December to February) holds 2% of the records.

Sauk County has the most records of venomous snakes in Wisconsin, 39, most of them of the timber rattlesnake. Pepin County and Grant County follow.

Winnebago County leads with 101 records (10%), followed by Juneau County and Sauk County; the top five counties hold 38% of the total. 66 of Wisconsin's 72 counties have at least one licensed snake record.

Wisconsin counties with their own page: Dane County and Vilas County.

Yes. Wisconsin has two venomous snake species on its list, the kind people usually call poisonous: timber rattlesnake and eastern massasauga. Strictly, snakes are venomous (they inject venom), not poisonous (harmful to eat or touch).

Yes. Two species are on the Wisconsin list: the timber rattlesnake and the eastern massasauga, with 58 licensed records between them. Most licensed records of the timber rattlesnake come from Sauk County, Pepin County and Grant County.

Not on our list: GBIF holds 1 copperhead record of any license in Wisconsin (eastern copperhead 1), fewer than 10 of any one species; such records can be genuine rarities, strays, transported animals or misidentifications. Treat any snake that looks like a copperhead or cottonmouth as venomous.

No. GBIF holds no cottonmouth record for Wisconsin under any license.

No. GBIF holds no coral snake record for Wisconsin under any license.

Wisconsin has 46 licensed records of the timber rattlesnake, which ranks the state 13th of the 30 states where it reaches our threshold. Most of its licensed records in Wisconsin come from Sauk County, Pepin County and Grant County. Range in other states and photos: Timber rattlesnake profile.

Wisconsin has 12 licensed records of the eastern massasauga, which ranks the state 8th of the 8 states where it reaches our threshold. Range in other states and photos: Eastern massasauga profile.

Many snakes and spiders taken for venomous ones are harmless species with a similar look. These are the usual confusions, with each species' licensed records in Wisconsin.

Copperheads are not on the Wisconsin list, but they are recorded in Wisconsin once (records of any license: eastern copperhead 1): treat any snake like this as venomous until identified. Harmless species often taken for them in the state: northern water snake (80), eastern milksnake (26), eastern hog-nosed snake (25) and eastern rat snake (1).

No cottonmouths reach the Wisconsin list, and GBIF holds no cottonmouth record for Wisconsin under any license, so a snake taken for one here is most likely a harmless lookalike. Those recorded in the state: northern water snake (80).

Rattlesnakes: 58 licensed records in Wisconsin. Harmless species often taken for them are also on the state list: eastern fox snake (78), eastern hog-nosed snake (25) and gopher snake (15). Together they have 118 licensed records, and the lookalikes are recorded 2.0 times as often.

No coral snakes reach the Wisconsin list, and GBIF holds no coral snake record for Wisconsin under any license, so a snake taken for one here is most likely a harmless lookalike. Those recorded in the state: eastern milksnake (26).

Widow spiders: 1 licensed record in Wisconsin. Harmless species often taken for them are also on the state list: triangulate bud spider (37), boreal combfoot (7), common house spider (4) and twospotted cobweb spider (on record). Together they have 48 licensed records, and the lookalikes are recorded 48 times as often.

Recluse spiders are not on the Wisconsin list, but they are recorded in Wisconsin two times (records of any license: brown recluse 2): treat any spider like this as venomous until identified. Harmless species often taken for them in the state: longbodied cellar spider (24) and spitting spider (6).

By count of venomous snake species, Wisconsin ranks 29th of 50 states, level with 7 other states. Nationally, Arizona leads with 14 species; five list none.

Of the four states bordering Wisconsin, Illinois and Iowa list more venomous snake species (Wisconsin: 2 species; Illinois 4, Iowa 3, Michigan 1, Minnesota 1).

Venomous snakes listed next door but not in Wisconsin: the northern cottonmouth (Illinois); the prairie rattlesnake (Iowa). Listed next door and recorded in Wisconsin too, but too few times to list (records of any license): the eastern copperhead, recorded here only one time (listed in Illinois). The most widely shared are the eastern massasauga and the timber rattlesnake, each listed in three of the four bordering states.

Yes. One widow species is on the Wisconsin list: the northern black widow (1 record).

Not on our list: GBIF holds 2 brown recluse records of any license in Wisconsin (brown recluse 2), fewer than 10 of any one species; such records can be genuine rarities, strays, transported animals or misidentifications. Treat any spider that looks like a recluse as venomous.

Wisconsin has 1 licensed record of the northern black widow, which ranks the state 28th of the 30 states where it reaches our threshold. Range in other states and photos: Northern black widow profile.

No. GBIF holds no scorpion record for Wisconsin under any license. Every scorpion has venom; only the Arizona bark scorpion's sting is medically significant, and it is not on the Wisconsin list.