How Can You Tell If a Snake Is Venomous & Other Questions About Snakes

Few things will send you scrambling to Google quicker than a snake sighting.

You may do so in fear or fascination, but you’re probably not indifferent to the issue. People tend to have strong feelings about snakes.

But no matter your motivation, I’m here to help you figure out whether the snake you saw was dangerous or not.

Fast Facts: How Can You Tell if a Snake is Venomous or Not?

Unfortunately, there is no simple way to distinguish venomous snakes from nonvenomous snakes.  

This includes all of the cute “rules,” songs and gimmicks you’ve heard. They are all wrong in some cases.

The good news is that there are a finite number of venomous species in any given geographic area. So, you’ll simply have to learn to identify the ones native to your region.

Don’t worry — it’s usually not that hard.

Image from Pixabay.

Venomous Snakes of the United States: An Overview

There are roughly 24 dangerously venomous snake species in the U.S.

I say “roughly” because different authorities embrace different classification schemes. Taxonomy is an incredibly fluid discipline, and biologists are constantly reorganizing the family tree of life (in very small ways).

This usually shouldn’t matter to the average person looking at a snake in the backyard, but it is part of the reason that venomous snake species lists may differ in number.

Minor details and disagreements aside, the list below includes all 24 of the dangerously venomous species in the United States.

  1. Eastern diamondback rattlesnake (Crotalus adamanteus)
  2. Western diamondback rattlesnake (Crotalus atrox)
  3. Mojave rattlesnake (Crotalus scutulatus)
  4. Sidewinder (Crotalus cerastes)
  5. Arizona black rattlesnake (Crotalus cerberus)
  6. Timber rattlesnake (Crotalus horridus)
  7. Black-tailed rattlesnake (Crotalus molossus)
  8. Tiger rattlesnake (Crotalus tigris)
  9. Ridge-nose rattlesnake (Crotalus willardi)
  10. Rock rattlesnake (Crotalus lepidus)
  11. Speckled rattlesnake (Crotalus mitchellii)
  12. Prairie rattlesnake (Crotalus viridis)
  13. Western rattlesnake (Crotalus oreganus)
  14. Twin-spotted rattlesnake (Crotalus pricei)
  15. Panamint rattlesnake (Crotalus stephensi)
  16. Red diamond rattlesnake (Crotalus ruber)
  17. Pigmy rattlesnake (Sistrurus miliarius)
  18. Massasauga (Sistrurus catenatus)
  19. Eastern coral snake (Micrurus fulvius)
  20. Texas coral snake (Micrurus tener)
  21. Western coral snake (Micruroides euryxanthus)
  22. Copperhead (Agkistrodon contortrix)
  23. Cottonmouth (Agkistrodon piscivorus)
  24. Yellow-bellied sea snake (Pelamis platurus)

But this list can’t help you by itself – no state is home to all of these species, and a few aren’t home to any.

But you can just consult the table below to determine which ones are native to your state.

Image from Wikipedia.
AlabamaCopperhead, cottonmouth, eastern coral snake, eastern diamondback rattlesnake, timber rattlesnake, pigmy rattlesnake
AlaskaNone
ArizonaWestern coral snake, western diamondback rattlesnake, sidewinder, Arizona black rattlesnake, rock rattlesnake, speckled rattlesnake, black-tailed rattlesnake, western rattlesnake, twin-spotted rattlesnake, Mojave rattlesnake, tiger rattlesnake, western rattlesnake, ridge-nosed rattlesnake, massasauga
ArkansasCopperhead, cottonmouth, western diamondback rattlesnake, timber rattlesnake, pigmy rattlesnake, Texas coral snake
CaliforniaWestern diamondback rattlesnake, sidewinder, speckled rattlesnake, western rattlesnake, red diamond rattlesnake, Mojave rattlesnake, Panamint rattlesnake, yellow-bellied sea snake
ColoradoWestern rattlesnake, massasauga
ConnecticutCopperhead, timber rattlesnake
DelawareCopperhead, timber rattlesnake
FloridaCopperhead, timber rattlesnake, cottonmouth, eastern coral snake, pigmy rattlesnake, eastern diamondback rattlesnake
GeorgiaCopperhead, cottonmouth, eastern diamondback rattlesnake, timber rattlesnake, pigmy rattlesnake, eastern coral snake
HawaiiYellow-bellied sea snake
IdahoWestern rattlesnake, prairie rattlesnake
IllinoisCopperhead, cottonmouth, timber rattlesnake, massasauga
IndianaCopperhead, cottonmouth, massasauga, timber rattlesnake
IowaCopperhead, massasauga, prairie rattlesnake, timber rattlesnake
KansasCopperhead, timber rattlesnake, cottonmouth (controversial)
KentuckyCopperhead, cottonmouth, timber rattlesnake, pigmy rattlesnake
LouisianaCopperhead, cottonmouth, timber (canebrake) rattlesnake, pigmy rattlesnake, eastern diamondback rattlesnake, eastern coral snake, Texas coral snake
MaineNone
MarylandCopperhead, timber rattlesnake
Massachusetts Copperhead, timber rattlesnake
MichiganMassasauga
MinnesotaTimber rattlesnake, massasauga
MississippiCopperhead, cottonmouth, timber (canebrake) rattlesnake, pigmy rattlesnake, eastern coral snake, eastern diamondback rattlesnake
MissouriCopperhead, cottonmouth, timber rattlesnake, pygmy rattlesnake, massasauga 
MontanaPrairie rattlesnake
NebraskaCopperhead, massasauga, timber rattlesnake, prairie rattlesnake
NevadaWestern diamondback rattlesnake, sidewinder rattlesnake, Great Basin rattlesnake, speckled rattlesnake, Mojave rattlesnake, prairie rattlesnake, western rattlesnake
New HampshireTimber rattlesnake, copperhead
New JerseyTimber rattlesnake, copperhead
New MexicoWestern diamondback rattlesnake, Arizona black rattlesnake, banded rock rattlesnake, black-tailed rattlesnake, Arizona black-tailed rattlesnake, Mojave rattlesnake, prairie rattlesnake, ridge-nosed rattlesnake, massasauga, western coral snake
New YorkTimber rattlesnake, copperhead, massasauga
North CarolinaTimber rattlesnake, copperhead, cottonmouth, eastern coral snake, pygmy rattlesnake, eastern diamondback rattlesnake
North DakotaPrairie rattlesnake
OhioTimber rattlesnake, copperhead, massasauga
OklahomaPrairie rattlesnake, western diamondback rattlesnake, copperhead, massasauga, cottonmouth, timber rattlesnake, pygmy rattlesnake
OregonPrairie rattlesnake
PennsylvaniaTimber rattlesnake, copperhead, massasauga
Rhode IslandNone
South CarolinaTimber rattlesnake, copperhead, cottonmouth, eastern diamondback rattlesnake, coral snake, pygmy rattlesnake
South DakotaPrairie rattlesnake
TennesseeTimber rattlesnake, copperhead, cottonmouth, pygmy rattlesnake
TexasWestern coral snake, prairie rattlesnake, cottonmouth, copperhead, western diamondback rattlesnake, massasauga, timber rattlesnake, rock rattlesnake, black-tailed rattlesnake, Mojave rattlesnake
UtahMojave rattlesnake, prairie rattlesnake, sidewinder, speckled rattlesnake
VermontTimber rattlesnake
VirginiaTimber rattlesnake, cottonmouth, copperhead
WashingtonPrairie rattlesnake
West VirginiaTimber rattlesnake, copperhead
WisconsinTimber rattlesnake, massasauga
WyomingPrairie rattlesnake, western rattlesnake
Image from Pixabay.

Mildly Venomous Snakes of the U.S.

You may have noticed a minor caveat included above.

I said it “all 24 of the dangerously venomous species in the United States.”

The reason for that disclaimer is that there are a number of species in the U.S. that are technically venomous, yet represent little danger to humans.

Image from Wikipedia.

In some cases, the venom these snakes produce is mild. It is unlikely to trigger serious or life-threatening symptoms (though it may cause some pain or swelling).

In other cases, the snakes are simply unable to open their mouths wide enough to bite something as large as a human finger.

And in a handful of cases, the snakes have fangs that are simply too short or located too far back in the mouth to present much of a threat.

These snakes occasionally cause medically significant symptoms, but these incidences tend to be the exception and not the rule. By and large, these snakes are rightfully considered harmless to humans.

The following list includes some of the most noteworthy species that fit into this category.

  • Hognose snakes (Heterodon spp.)
  • Ringneck snakes (Diadophis punctatus)
  • Red-bellied snakes (Storeria occipitomaculata)
  • Lyre snakes (Trimorphodon spp.)
  • Night snakes (Hypsiglena spp.)
  • Garter snakes (Thamnophis spp.)
  • Black-headed snakes (Tantilla spp.)
Image from Wikipedia.

It’s also worth noting that scientists are continually finding that species long considered non-venomous actually do produce venom.

For example, researchers have recently found that some rat snakes produce venom-like proteins in their saliva. This doesn’t mean that you need to fear rat snakes, nor do you need to consider them dangerous — they still lack fangs, so they don’t have an effective way to inject venom. For that matter, scads of people are bitten by rat snakes each year, and medically significant symptoms are essentially unheard of.

Snake FAQs

Given the fear, fascination and intrigue they inspire, it’s not surprising that snakes are the subject of countless questions among nature lovers. We’ll try to answer a few of the most common ones below.

What should you do when you find a snake?

Generally speaking, nothing.

It is a good idea to get a look at the critter in question. A photo would be even better, but it’s often surprisingly difficult to safely obtain a decent photo of a snake when confronted with one.

But aside from snapping a photo (from a safe distance), don’t do anything else. If you don’t feel safe living near the snake, call a professional to remove it for you. Don’t try to remove or kill it yourself — the vast majority of venomous snake bites that occur in the U.S. are the result of people deliberately interacting with snakes.

Do venomous snakes have triangular or diamond-shaped heads?

Some do; others don’t.

Most vipers and pit vipers do have distinctly triangular or diamond-shaped heads. But elapids — including the coral snakes of the U.S., as well as cobras, kraits, taipans and sea snakes — have round heads.

Additionally, many non-venomous and mildly venomous snakes will flatten their heads when frightened, which can make them appear triangular.

Water snakes (Nerodia spp.) and rat snakes (Pantherophis spp.) provide two common examples of this phenomenon.

How can you tell a coral snake from a harmless mimic?

In the United States, you can distinguish coral snakes from their many harmless mimics by noting the sequence of their colored bands. In coral snakes native to the U.S., the red and yellow bands are adjacent; U.S. mimics always have black bands between their yellow and red rings.

As the saying goes, “red touch yellow kills a fellow; red touch black venom lack.”

But, as discussed at the outset, this rule fails miserably in some other parts of the world, including most notably Central and South America. In these places, you may find coral snakes and their mimics breaking this “rule.”

Do water moccasins crawl on dry land?

Sure. Water moccasins are typically described as being semi-aquatic. They do swim and hunt in water, but they’re more commonly encountered on dry land — mostly because that’s where humans spend more time.

You won’t find water moccasins venturing far from water very commonly, but it can and does happen.

Can rattlesnakes swim?

All snakes can swim from the time of their birth or hatching. Some are better swimmers or more comfortable in the water than others, but all snakes can swim.

Are baby snakes more dangerous than adults?

Eh, not really.

“Dangerous” is a hard adjective to quantify in this sense, so this is a question without an easy answer.

Most adult snakes are thought to be capable of metering the amount of venom they deliver when biting. By contrast, young snakes are thought to have much less control over the amount of venom they inject when biting.

This only matters because some venomous snake species have been observed injecting more venom when biting prey than when biting perceived predators.

Venom is a finite and invaluable resource for snakes that possess it, so it makes sense that they’d ration it carefully (they constantly produce venom, but this is a time-consuming process).

So, the thinking goes, a baby is likely to juice you pretty good when it bites, but an adult is more likely to restrict the amount of venom expelled.

But there are a ton of problems with this line of thought.

In some cases, the “reduced” dose of venom may be more than enough to end your life. Then, there’s the size discrepancy: Even if an 6-foot-long eastern diamondback rattlesnake only injects X percent of the venom it has, that may amount to much more than a baby diamondback has available.

Multiple bites would also render this issue irrelevant (if the first bite didn’t scare you away, an adult is unlikely to be as restrained in follow up bites). And for that matter, the larger size and (often) greater confidence level of adult snakes means that they’re more likely to achieve solid bites than tiny juveniles are.

Do venomous snakes have cat eyes (elliptical pupils)?

Some do, but others don’t.

Pit vipers have elliptical pupils, while most non-venomous snakes in the U.S. have round pupils.

But exceptions occur. Cat-eyed snakes (Leptodeira annulata) and (Trimorphodon spp.) have slit-like pupils, and they’re only mildly venomous. And coral snakes — who’re deadly — have round pupils.

Historically, pupil shape was thought to be related to activity pattern. Diurnal snakes would have round pupils, while nocturnal snakes would have elliptical pupils. But more recent research strongly suggests that it is more closely tied to hunting style, with ambush hunters having cat eyes and prowling species have round pupils.

Whether welcomed or frightening, snake sightings are exciting for most people. But in all cases, your reaction should be pretty similar: Don’t mess with it, snap a photo if you can, and then tag us on social media.

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