How to Tell if a Snake is “Poisonous”

Summer is in full swing, and with summer comes hiking!!! (among other outdoor activities, of course) You know who else loves summer, though? Snakes! Learn how to tell if a snake is poisonous so you can frolic safely.

Blog graphic - how to tell if a snake is poisonous

How NOT to tell if a snake is venomous

You’ve probably seen this chart floating around:

FALSE Venomous vs. Nonvenomous snake chart

This chart is WRONG!

Granted, it is useful for identifying rattlesnakes and other vipers (although I’m not entirely sure about the subcaudal scales bit — either way, you shouldn’t be examining the tail of a snake you don’t know). But in terms of identifying venomous snakes in general, it’s bogus.

There are several snakes with round eyes and oval heads that are actually extremely venomous.

For example:

This is a black mamba (Dendroaspis polylepis), native to parts of sub-Saharan Africa. Don’t be deceived by the cuteness — it’s actually one of the most dangerous snakes in the world!

This is a king cobra (Ophiophagus hannah), native to forested areas in India as well as other parts of Southeast Asia. Round pupils? Check. Venom? You’d better believe it.

There are also lots of snakes with slit pupils that aren’t venomous at all!

Image by aixklusiv from Pixabay

This is a ball python (Python regius), native to west and central Africa, and one of the most common snakes in the American pet trade. Slit eyes? Absolutely. Venom? Not at all!

This is a green tree python (Morelia viridis), native to New Guinea, parts of Indonesia, and the Cape York Peninsula in Australia. Its acid-green color, prominent heat pits, and slitted eyes might lead you to believe that it’s venomous, but there’s no venom here, either.

And then there’s the snake that looks evil and scary enough that it must be venomous:

Nope! This is an eastern indigo snake (Drymarchon couperi), native to the eastern U.S. Many people mistake them for black mambas because of the scary appearance, even though real black mambas are not native to the US and have gray rather than black scales. Fun fact: eastern indigos actually EAT venomous snakes!

So if you can’t tell a venomous snake by its eyes, head shape, or the presence of heat pits, then how can you tell? Is it all just a guessing game?

How to tell if a snake is poisonous…I mean venomous

1) Ask yourself: Is it a viper?

All vipers are venomous, so if you can identify one, you’re in good shape.

  • triangular head
  • fat/stocky body
  • rough scales

There are 3 types of vipers native to the US:


Image by M. Maggs from Pixabay


Image by skeeze from Pixabay

Cottonmouth/Water Moccasin

2) Know the snakes in your area.

I know. This means you have to research. Lame. But because snakes are diverse and beautiful, it’s really hard to create a general rule for identifying which ones are venomous. All it takes is a quick Google search to find names and pictures of the snakes to look out for in your part of the world. 

The World Health Organization has a really excellent database of venomous snakes categorized by region here. And if you’re in Australia…I’m sorry.

There are only 4 types of venomous snake to look out for in the United States. 3 of those are the vipers I mentioned above. The last one is the coral snake, which is the only venomous snake in the U.S. that is not a viper:

Some snakes that aren’t venomous look a lot like snakes that are venomous. If you’re not sure whether the snake that has crossed your path is venomous or not, here’s a handy rule of thumb: When in doubt, leave it alone!

The majority of venomous snakebites that occur in the U.S. happen because a stupid person bothered a snake that didn’t want to be bothered (not because the snake chased them — that’s a complete and total MYTH!!). If you have been bitten, though, I recommend reading through the solid tips in this article.

As a final note, please enjoy this cartoon about the difference between venomous and poisonous. Learn the difference and impress — or annoy —your friends with your superior knowledge!

Venomous vs. poisonous snakes

(Of course, according to the Merriam-Webster dictionary, “venomous” and “poisonous” can be synonymous. So please don’t go jumping down people’s throats about not using the “proper” word — unless you’re both scientists, both words get the point across just fine!)


  1. There are some in the genus Rhabdophis that are actually poisonous and venomous. Pretty facsinating actually.