Venomous Snakes of North America: Regional Identification Guide

Pit Vipers (Crotalidae) — Majority of North American Venomous Snakes

Pit vipers account for approximately 95% of venomous snakebites in North America. All have heat-sensing facial pits and produce predominantly hemotoxic (tissue and blood-destroying) venom, though some species also have significant neurotoxic components.

Rattlesnakes — Multiple Species

Timber Rattlesnake (Crotalus horridus)

• Range: Eastern US from Minnesota south to Florida, northeast to New Hampshire
• Length: 90-150cm
• Appearance: Heavy-bodied, gray-brown or yellow-brown with dark crossbands or chevrons, distinct rattle
• Habitat: Rocky wooded hillsides, river floodplains, mixed forests
• Clinical significance: Major envenomation potential; significant cytotoxic venom; medically serious

Eastern Diamondback Rattlesnake (Crotalus adamanteus)

• Range: Coastal plain from southeast North Carolina to eastern Louisiana, including Florida
• Length: 100-180cm — the largest venomous snake in North America
• Appearance: Brown or olive with distinctive diamond pattern and black-and-white banded tail
• Clinical significance: The most dangerous rattlesnake in North America by mass of venom injected; large fang length means deep envenomation

Western Diamondback Rattlesnake (Crotalus atrox)

• Range: Southwest US from Arkansas to California, into Mexico
• Length: 90-160cm
• Appearance: Gray-brown with diamond/hexagonal dorsal pattern, distinct black-and-white banded tail ("coontail rattler")
• Clinical significance: Responsible for the most snakebite deaths in the US; potent cytotoxic and hemotoxic venom

Prairie Rattlesnake (Crotalus viridis)

• Range: Great Plains from Canada south to New Mexico, west to eastern Montana/Wyoming
• Length: 90-120cm
• Appearance: Greenish-gray or brown with rounded blotches, distinct rattle
• Habitat: Prairies, open grasslands, rock outcroppings

Mojave Rattlesnake (Crotalus scutulatus)

• Range: Mojave Desert of California, Nevada, Utah, Arizona
• Length: 60-100cm
• Appearance: Greenish or pale brown with diamond pattern
• Clinical significance: Has both hemotoxic AND significant neurotoxic (Type A venom) components in some populations — can produce respiratory paralysis in addition to tissue destruction. Potentially the most medically dangerous rattlesnake gram-for-gram.

Sidewinder (Crotalus cerastes)

• Range: Mojave and Sonoran deserts
• Length: 45-80cm
• Appearance: Small, pale tan/cream, distinctive horn-like scales over each eye
• Movement: Sidewinding locomotion on loose sand
• Clinical significance: Small snake, relatively mild envenomation in most cases

Northern Pacific Rattlesnake (Crotalus oreganus)

• Range: Pacific Coast from British Columbia to Baja California, inland to Rocky Mountains
• Length: 60-100cm
• Appearance: Brown or olive with blotch pattern

Massasauga (Sistrurus catenatus)

• Range: Great Lakes region, Ohio, Pennsylvania south to Texas
• Length: 45-75cm; smaller than most rattlesnakes
• Appearance: Gray-brown with darker dorsal blotches
• Clinical significance: Venom is potent but small snake means less venom per bite; medically significant but typically less severe than larger rattlesnakes

Copperhead (Agkistrodon contortrix)

• Range: Eastern US from Massachusetts to Nebraska, south to Texas and Florida panhandle; most widespread venomous snake in the East
• Length: 60-90cm
• Appearance: Distinctive hourglass/chestnut crossbands on a copper-brown background — identification is usually straightforward
• Habitat: Rocky hillsides, forest edges, suburban areas with rock piles or brush
• Venom: Primarily cytotoxic, rarely fatal in healthy adults; significant tissue damage is possible
• Clinical significance: Responsible for more snakebite bites than any other US species (partly because of suburban overlap); most bites are painful and require treatment but fatal outcomes are rare

Cottonmouth / Water Moccasin (Agkistrodon piscivorus)

• Range: Southeast US from Virginia to Florida, west to Texas, north to southern Illinois
• Length: 60-120cm; heavy-bodied
• Appearance: Dark olive-brown to black with indistinct banding in adults (juveniles have visible copper-brown crossbands and resemble copperheads); distinctive white mouth lining visible when threatened
• Habitat: Aquatic — streams, swamps, drainage ditches, pond edges; often found basking on logs or branches over water
• Behavior: Will stand its ground; the open-mouth "cottonmouth" display is a threat display, not an attack
• Clinical significance: Potent cytotoxic venom; more aggressive than other pit vipers; significant tissue damage common

Coral Snakes (Elapidae)

Coral snakes are elapids, not pit vipers. They have small mouths, round pupils, and neurotoxic venom. They must chew to inject venom effectively — a quick bite-and-release often results in minimal envenomation, but prolonged contact allows significant venom delivery.

Eastern Coral Snake (Micrurus fulvius)

• Range: Southeast US from North Carolina to Florida, west to eastern Texas
• Length: 50-80cm
• Appearance: Bright bands of red, yellow, and black — red touches yellow (key distinguishing feature from scarlet king snake)
• Habitat: Wooded areas, sandy uplands, suburban areas
• Venom: Neurotoxic — causes progressive muscle weakness and respiratory paralysis; minimal local tissue reaction (deceivingly benign early appearance)
• Clinical significance: Delayed symptom onset 4-8 hours after bite; once neurological symptoms begin they progress rapidly; no FDA-approved antivenom currently produced in the US (Wyeth antivenom manufacturing discontinued, limited strategic stockpile exists)

Texas Coral Snake (Micrurus tener)

• Range: Arkansas, Louisiana, Texas, into Mexico
• Similar appearance and venom profile to Eastern

Arizona Coral Snake / Sonoran Coral Snake (Micruroides euryxanthus)

• Range: Arizona, New Mexico, into Mexico
• Length: 35-55cm — smallest US venomous snake
• Less clinically significant than Eastern and Texas coral snakes; rarely causes serious envenomation

Regional Quick Reference

| Region | Primary Venomous Snakes to Know | |---|---| | Northeast (New England, NY, PA, NJ) | Timber rattlesnake, Copperhead | | Southeast (GA, FL, SC, NC, AL, MS) | Eastern diamondback rattlesnake, Copperhead, Cottonmouth, Eastern coral snake | | Gulf Coast (TX, LA) | Western diamondback, Copperhead, Cottonmouth, Texas coral snake | | Midwest (OH, IN, IL, MO, KS) | Timber rattlesnake, Copperhead, Eastern massasauga, Cottonmouth (southern areas) | | Southwest (AZ, NM) | Western diamondback, Mojave rattlesnake, Arizona coral snake, various mountain rattlesnakes | | Pacific Coast (CA, OR, WA) | Northern Pacific rattlesnake (only venomous snake in WA/OR); multiple rattlesnake species in CA | | Great Plains (TX north to SD) | Prairie rattlesnake, Western diamondback (southern), Massasauga | | Mountain West (CO, UT, NV) | Prairie rattlesnake, Mojave rattlesnake (desert areas), Great Basin rattlesnake |

Distinguishing Venomous from Non-Venomous

Reliable pit viper characteristics:

• Triangular head distinctly wider than the neck
• Elliptical/vertical (cat-eye) pupils
• Heat-sensing pit between eye and nostril
• Single row of subcaudal scales (under the tail)

Unreliable field indicators:

• Head shape can be hard to assess safely
• Non-venomous snakes flatten their heads when threatened, mimicking the triangular shape
• Water snakes are frequently mistaken for cottonmouths
• Banded patterns occur in many non-venomous species

The safest rule: Leave any snake you cannot positively identify alone. If someone is bitten, attempt to photograph the snake from a distance — do not attempt to capture or kill it, which causes additional bites.