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