Tuesday, June 21, 2011

Can Cottonmouths Bite Underwater?


A few years ago, I was asked to comment on a proposed snake exhibit in a local nature-themed education center. The exhibit was going to be a large swampy area, complete with water snakes, Cottonmouths, and various other wetland reptiles, like turtles.  Although I personally would have enjoyed viewing such a display, I warned those at the nature center that the exhibit was unlikely to be very diverse for very long. Eventually, I predicted, the entire display would have consisted of a few very fat and very content Cottonmouths.

Cottonmouths can become abundant in suitable wetland habitats, such as beaver ponds and creeks.  My hunch is that they can thrive in these wetlands because they are not picky about what they eat. And, when an animal eats just about anything, there’s a smaller chance that they will go hungry or compete for scraps with other individuals of the same species. As a result, Cottonmouths can eat, grow large, and reproduce with relatively little holding them back.

Cottonmouths can and do eat insects, frogs, salamanders, turtles, rodents, birds, and other snakes, even including individuals of their own species. But, given their aquatic tendencies, you may not be surprised to find out that their primary prey item is often fish. Since fish spend their time underwater, it is also not surprising that this is where Cottonmouths find and capture them….with their mouths.

Yet, a myth persists that Cottonmouths can’t bite underwater. They surely can, and people should be as careful of them underwater as they are on land. This is not to say that Cottonmouths present a considerable risk or danger to swimmers. No Cottonmouth is so lazy or distracted enough to allow a casual bather to step on it; any snake is likely to be long gone before you even come close. Alternatively though, Cottonmouths may also use a different defensive strategy, specifically floating on top of the water (or on some vegetation) shaking their tails, and flashing their white mouths to discourage you from getting too close. And if that doesn’t convince you to walk away, I don’t know what will. You can’t say the snake didn’t warn you.



This isn't the first time I've written about Cottonmouths.  For a discussion of Cottonmouths allegedly dropping into boats, click here. Or, to read about breeding balls, click here. To learn about where in the world you can find Cottonmouths, and where you can't, click here. Worried about getting chased down by one of these snakes? Then you need to read this.

I wrote about how these snakes are quick to show up when a lot of toads (= food) appear here.  I've also written about accompanying Cottonmouth researchers as they wade through swamps to catch snakes in the spring as the reptiles try to take advantage of the new warmth and at night in the summer as the venomous snakes swam around me.  Finally, I provide some tips on recognizing Cottonmouths from non-venomous watersnakes here.

The first Cottonmouth picture is provided courtesy of Fingerprince Prints.

Much of what I write is based on my experience in the field, however I also rely on the research of others, citations of some relevant scientific articles are below.

Vincent, S., Herrel, A., & Irschick, D. (2004). Sexual dimorphism in head shape and diet in the cottonmouth snake (Agkistrodon piscivorus) Journal of Zoology, 264 (1), 53-59 DOI: 10.1017/S0952836904005503


Ian Nance said...

A cypress swamp on our lease dried out last year; it was like a cottonmouth migration out of there. I've watched them in South Florida sit at the end of spillways and streams and pick off passing frogs and fish. Very efficient.

David Steen said...


There has been some recent research out of the Savannah River Ecology Laboratory in SC that describes the phenomenon you observed (i.e. cottonmouth migrations in response to drought). Interesting stuff.


Michael said...

I've seen from several sources, often people who catch them, that snapping turtles don't bite underwater. I have one in my lab, so I know they do, but do you know why people who nab them in the wild seem to think that they don't?

David Steen said...


Thanks for your comment. I've heard this rumor regarding snapping turtles as well. Have you heard the one about how once a snapping turtle bites down on you, it won't let go until it thunders?

I imagine that snapping turtles feel much more secure in the water, and are therefore less likely to bite to defend themselves (which is the only reason they do so on land).

Perhaps a good topic for a future blog.