Venomous snakes and spiders in Idaho
Idaho has two venomous snake species among the 11 snake species listed there: western rattlesnake and prairie rattlesnake. The western rattlesnake accounts for the most records (195), and venomous species make up 18% of all 1,474 licensed snake records in the state. On the spider side, one species is medically significant: western black widow.
Venomous snakes of Idaho
Idaho's venomous snakes are two rattlesnake species. Together they account for 258 licensed records; the western rattlesnake alone has 76% of them, and the least recorded, the prairie rattlesnake, has 63.
Dangerous spiders of Idaho
One widow species (Western black widow: 16 records) is on the Idaho list. There is no recluse spider on the Idaho 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.
Are there scorpions in Idaho?
Yes. Three scorpion species are recorded in Idaho, from 6 licensed records: Black hairy scorpion (3 records), Northern scorpion (2 records), Yellow ground scorpion (on record). Every scorpion has venom; only the Arizona bark scorpion's sting is medically significant, and it is not on the Idaho list.
Other snakes recorded most in Idaho
These eight account for 81% of all licensed snake records in Idaho; the most recorded, the western terrestrial garter snake, alone for 42%.
Other spiders recorded most in Idaho
These eight account for 55% of all licensed spider records in Idaho; the most recorded, the bold jumper, alone for 14%.
When venomous snakes are out in Idaho
Observation records of venomous snakes in Idaho run mostly April through August, peaking in July with 30% of them. December through February together hold under 2% of the records, so venomous snakes in Idaho are rarely recorded in winter.
When spiders are most active in Idaho
Observation records of spiders in Idaho run mostly March through September, peaking in May with 19% of them. Winter (December to February) holds 5% of the records.
Counties with the most venomous snake records
Ada County has the most records of venomous snakes in Idaho, 77, most of them of the western rattlesnake. Adams County and Lemhi County follow.
| # | County | Records | Most recorded there |
|---|---|---|---|
| 1 | Ada County | 77 | Western rattlesnake |
| 2 | Adams County | 24 | Western rattlesnake |
| 3 | Lemhi County | 21 | Prairie rattlesnake |
| 4 | Elmore County | 17 | Western rattlesnake |
| 5 | Owyhee County | 15 | Western rattlesnake |
| 6 | Bannock County | 15 | Western rattlesnake |
| 7 | Idaho County | 14 | Western rattlesnake |
| 8 | Nez Perce County | 13 | Western rattlesnake |
| 9 | Butte County | 10 | Prairie rattlesnake |
| 10 | Canyon County | 7 | Western rattlesnake |
Where in Idaho are snakes recorded most?
Ada County leads with 279 records (19%), followed by Bannock County and Owyhee County; the top five counties hold 45% of the total. 42 of Idaho's 44 counties have at least one licensed snake record.
| # | County | Records | Share |
|---|---|---|---|
| 1 | Ada County | 279 | 18.9% |
| 2 | Bannock County | 113 | 7.7% |
| 3 | Owyhee County | 99 | 6.7% |
| 4 | Bonneville County | 98 | 6.6% |
| 5 | Idaho County | 74 | 5.0% |
| 6 | Blaine County | 72 | 4.9% |
| 7 | Valley County | 69 | 4.7% |
| 8 | Bingham County | 66 | 4.5% |
| 9 | Latah County | 53 | 3.6% |
| 10 | Caribou County | 49 | 3.3% |
| 11 | Adams County | 46 | 3.1% |
| 12 | Kootenai County | 41 | 2.8% |
Are there poisonous snakes in Idaho?
Yes. Idaho has two venomous snake species on its list, the kind people usually call poisonous: western rattlesnake and prairie rattlesnake. Strictly, snakes are venomous (they inject venom), not poisonous (harmful to eat or touch).
Are there rattlesnakes in Idaho?
Yes. Two species are on the Idaho list: the western rattlesnake and the prairie rattlesnake, with 258 licensed records between them. Most licensed records of the western rattlesnake come from Ada County, Adams County and Elmore County.
Are there copperheads in Idaho?
No. GBIF holds no copperhead record for Idaho under any license.
Are there cottonmouths (water moccasins) in Idaho?
No. GBIF holds no cottonmouth record for Idaho under any license.
Are there coral snakes in Idaho?
No. GBIF holds no coral snake record for Idaho under any license.
Western rattlesnake (Crotalus oreganus)
Idaho has 195 licensed records of the western rattlesnake, which ranks the state 5th of the 9 states where it reaches our threshold. Its observation records in Idaho run mostly April through August, peaking in July; most licensed records come from Ada County, Adams County and Elmore County. Range in other states and photos: Western rattlesnake profile.
Prairie rattlesnake (Crotalus viridis)
Idaho has 63 licensed records of the prairie rattlesnake, which ranks the state 12th of the 14 states where it reaches our threshold. Most of its licensed records in Idaho come from Lemhi County, Ada County and Butte County. Range in other states and photos: Prairie rattlesnake profile.
Harmless lookalikes in Idaho
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 Idaho.
What looks like a rattlesnake in Idaho
Rattlesnakes: 258 licensed records in Idaho. Harmless species often taken for them are also on the state list: gopher snake (204). It has 204 licensed records, and the two sides are recorded about equally.
What looks like a widow spider in Idaho
Widow spiders: 16 licensed records in Idaho. Harmless species often taken for them are also on the state list: triangulate bud spider (9) and false black widow (1). Together they have 10 licensed records, and here the venomous species are the more recorded side, 1.6 to 1.
What looks like a recluse spider in Idaho
No recluse spiders reach the Idaho list, and GBIF holds no recluse spider record for Idaho under any license, so a spider taken for one here is most likely a harmless lookalike. Those recorded in the state: hobo spider (9), longbodied cellar spider (1) and spitting spider (on record).
How Idaho compares
By count of venomous snake species, Idaho ranks 29th of 50 states, level with 7 other states. Nationally, Arizona leads with 14 species; five list none.
Of the six states bordering Idaho, Nevada and Utah list more venomous snake species; Wyoming lists as many (Idaho: 2 species; Nevada 6, Utah 5, Wyoming 2, Montana 1, Oregon 1, Washington 1).
Venomous snakes listed next door but not in Idaho: the Mohave rattlesnake (Nevada and Utah); the sidewinder (Nevada and Utah); the southwestern speckled rattlesnake (Nevada and Utah); the Panamint rattlesnake (Nevada); the western diamondback rattlesnake (Nevada). The most widely shared is the western rattlesnake, listed in five of the six bordering states.
Are there poisonous spiders in Idaho?
Does Idaho have black widows?
Yes. One widow species is on the Idaho list: the western black widow (16 records).
Does Idaho have brown recluse spiders?
No. GBIF holds no brown recluse record for Idaho under any license.
Western black widow (Latrodectus hesperus)
Idaho has 16 licensed records of the western black widow, which ranks the state 10th of the 18 states where it reaches our threshold. Range in other states and photos: Western black widow profile.
More for Idaho
GBIF records read 2026-09-29. Listed: any license. Counted: CC0/CC BY only. How we count.