Venomous vs. Poisonous

As a herpetologist, one of my biggest pet peeves is the incorrect usage of the words venomous and poisonous. Another huge pet peeve is calling an amphibian a reptile (salamanders and geckos are not the same! but we’ll save that rant for another day :) ). Most people don’t understand that there is a difference between an organism being venomous or poisonous.

To be venomous, an animal must be able to inject a toxin. The common delivery systems are fangs and stingers. The toxin is typically stored internally usually in specialized glands. A great example of a venomous animal is a rattlesnake. All toxic snakes are venomous and not poisonous, well all of them except one and possibly more (because as with everything in nature there is an exception). The Asian tiger snake is both poisonous and venomous (see below).

Poison, on the other hand, is a toxic substance that is usually secreted from an organism’s external covering, be it skin or leaves. Poisons are not injected instead they have to come in contact with skin or be ingested to cause harm. Poison dart frogs and poison ivy are examples of poisonous organisms.

So the next time someone yells that they’ve been bitten by a poisonous snake you can politely correct them while en route to the nearest hospital unless of course you are in the Asian tiger snake’s range.  😛

Venomous Poisonous

Northern Pacific Rattlesnake

Northern Pacific Rattlesnake

 

Venomous Poisonous

Rough-skinned-Newt

Rough-skinned-Newt

 

A paper published in 2007 documented an actual poisonous snake. It turns out that the Asian tiger snake (Rhabdophis tigrinus, AKA Keelback, AKA Yamakagashi), and possibly a few other members of the Rhabdophis genus, is able to sequester toxins from toads it consumes and secrete them from specialized glands in the neck. Snakes of this species that live in toad-free environments don’t have the poison. It seems this snake is also venomous with rear fangs. So this species is a poisonous venomous snake! Read abstract.

Poisonous and Venomous

Tiger Keelback (c)2009 Yasunori Koide

Tiger Keelback (c)2009 Yasunori Koide

A paper published in 2015 documented two species of venomous frogs. Yes, you read that correct, venomous frogs. Apparently, the Greening’s frog (Corythomantis greeningi) and the Bruno’s casque-headed frog (Aparasphenodon brunoi) have toxic spines on their heads. They headbutt potential predators with the spikes, injecting them with the toxins. Since the toxins are injected, this makes the frogs venomous instead of just poisonous. Read paper.

Venomous

Head Spines of Aparasphenodon brunoi and Corythomantis greeningi (c)2015 Jared et al.

On this same line, the three species of Pluerodeles ribbed newts would also be considered venomous since they use their toxic tipped ribs, which pierce through special toxin glands in their skin, to inject toxins into predators.

 

Here’s a great cartoon by Bird and Moon explaining the difference:

Toxic (c)2015 Bird and Moon

Toxic (c)2015 Bird and Moon

 

 

Disclaimer: The views expressed in this post are solely this author's and do not necessarily reflect the views of The Wandering Herpetologist website.
Sara Viernum

Author: Sara Viernum

Sara is a herpetologist with over 10 years experience. She started this blog in June, 2011 as a way to share and promote information about herps.Gotta a question or comment for Sara? Email her at sara[at]wanderingherpetologist.com

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10 Comments

  1. There are actually a lot of poisonous snakes. Some of nuchal glands in the neck like the genus Rhabdophis, and some sequester toxins in their liver and other tissues.

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    • have* nuchal glands. Since I am correcting that, I suppose I will mention the other two genera so far described with poisonous nuchal glands allowing snakes to squirt poison from their neck (up to a meter documented in Rhabdophis) are Balanophis and Macropisthodon (all but one species have the glands).

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  2. Hognose snakes seem to be poisonous also. They rarely bite though usually it only strikes if the handlers hand smells of prey. But I’ve read of some nasty swelling from pet hogs.

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  3. I think I read recently that garter snakes have actually been found to be poisonous via the consumption of newts. But that doesn’t really count.

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    • Sara Viernum

      Ethan you wouldn’t know where you read that info do you? I would really like to find out if the snakes are sequestering the newt toxins

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      • I found the information on the “poisonous” garter snakes while researching venomous snakes for home school for my grandsons.
        Three species of garter snakes that are cousins to the Asian tiger snake obtain poison in the same way, but store it in their bodies.
        The spitting cobra can also be considered “poisonous” since it’s venom acts as an irritant to the skin, and particularly the eyes. I don’t know what result drinking it would have, though.

        “Although Garter Snakes simply retain the poisons they acquire from newt prey (tetrodotoxin, abbreviated TTX) in their bodies for some time following a meal, Tiger Keelback snakes actively sequester the poisons they acquire from toad prey (bufotoxins, specifically bufadienolides) in a poison gland on the back of their neck (called the nuchal gland), enabling them to remain poisonous for much longer following a meal. So, basically these four snakes possess two different types of toxins in different places in their bodies, which come from different sources, and serve different purposes.”
        “So, if anyone ever asks you how many of the ~3150 species of snakes in the world are poisonous, you can give them an answer of at least four species (Thamnophis sirtalis/couchii/atratus and Rhabdophis tigrinus), with the caveat that they are both poisonous and venomous. Aside from those species, the remaining snakes in the world are either nonvenomous/nonpoisonous or venomous, with constrictors belonging to either of those categories.”
        http://christopherjrex.hubpages.com/hub/What-is-snake-venom-poison

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        • Is Coral snake poisonous and or venomus? I don’t think they have a way of injecting venom.

          Post a Reply
          • Sara Viernum

            Coral snakes are venomous. They have small, fixed fangs and usually deliver venom to their prey with a chewing motion.

  4. Fully agree! It also saddens me to see “experts” on Animal Planet using the words itnerchangeably while talking about the same animal.

    Post a Reply
    • Sara Viernum

      Very true. It doesn’t help people outside the field learn that there is a difference if professionals use the incorrect word as well.

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