Wednesday, March 20, 2013

Are Cottonmouths Aggressive?

            A few years ago I was walking alongside the edge of pond in the Florida panhandle when I was startled by some splashing noises in the water. I had accidentally gotten too close to a Cottonmouth (Agkistrodon piscivorus) and the snake was warning me away by vibrating its tail in the water and flashing its white mouth. It was obvious to me that the snake thought I was getting too close and it was warning me away before things got serious. Neither of us wanted to be involved in a venomous snakebite.

            One of the myths I hear most frequently about Cottonmouths is that they are aggressive. It seems that whenever I talk or write about the species, someone wants to tell me a story about how one of the snakes chased them around a swamp all the while menacing them with their fangs and the potential of a venomous bite. The Cottonmouth’s reputation is not helped by educational websites that say that the animals, “are aggressive snakes and bite when disturbed or provoked…” but also “generally secretive and are not aggressive, so bites are rare”.

            I’ve heard stories about aggressive Cottonmouths so many times that they are hard to discount. But I believe, as with so many other Cottonmouth myths, that normal snake behavior is being misinterpreted. For one thing, a Cottonmouth has nothing to gain by being aggressive towards large potential predators like people. In any case, after hearing this story one too many times, a couple researchers in South Carolina decided to test just how a Cottonmouth reacted when confronted by a human. In their words, “We examined defensive behavior of wild cottonmouths in response to a human aggressor by subjecting them to one or more of three different treatments. When we encountered a cottonmouth in the field, we approached the snake and either (1) stood beside it with a "snakeproof" boot touching its body, (2) stepped on the snake at midbody with enough force to restrain but not injure it, or (3) picked up the snake at midbody with a pair of 1-m snake tongs (Whitney Tongs) with a grasping handle that was modified to resemble a human arm and hand. A leather glove was fitted over the end of the tongs, with one extension covered by the thumb and the other by the middle finger. Hence, the glove could be closed around the snake's body. A padded shirt sleeve was used to cover the remainder of the rod up to the handle. Each treatment was carried out for 20 sec, and the behavior of each snake was recorded.”

            In other words, they walked up to Cottonmouths, stepped on Cottonmouths, and picked up Cottonmouths with fake arms and watched what happened. Who said science wasn’t entertaining? They ended up standing alongside 13, stepping on 22, and picking up 36 snakes. None of the snakes they stood beside tried to bite, one of the snakes they stepped on bit them and just 13 (36%) of the picked-up snakes bit the fake arm. Overall, most snakes either tried to escape or gave defensive displays to scare off the people without trying to bite. There are two primary lessons here: Cottonmouths aren’t eager to bite even when they are harassed and you shouldn’t try to pick up Cottonmouths (although if you are inclined to pick up venomous snakes then a scientific paper may not be enough to convince you to do otherwise).

            So what about all these stories of Cottonmouths chasing people? I have long argued that when a Cottonmouth is scared it will head right for the water and if you are in between the Cottonmouth and where that Cottonmouth wants to go, it will come right at you. Again, we can go to the scientific literature to find an experiment on the subject. A study was undertaken in Florida to evaluate how Cottonmouths behaved after you A) scared them into trying to escape and then B) stepped in front of them. As you might expect, the Cottonmouths were pissed off! From the study, Cottonmouths, “…exhibited several characteristic behaviors, including crawling rapidly toward me, raising the head and neck off the ground, expanding the jaws, flattening the body, vibrating the tail, tongue-flicking, lunging and striking forward, and rarely, musk-squirting. A great deal of variation exists in the intensity of these behaviors.”

        What’s the lesson here? When you see a Cottonmouth that looks like it is going somewhere…Let it go.

   The author concludes, “I believe that the, “...'aggressive bluffing' behavior I have witnessed…were elicited under the special circumstances of encountering the snakes in habitats familiar to them and by blocking their escape along a direction they had chosen.” 

     What do you conclude?

Want to learn more? Check out these scientific articles or read my previous posts on Cottonmouth myths.

Gibbons, J., & Dorcas, M. (2002). Defensive Behavior of Cottonmouths (Agkistrodon piscivorus) toward Humans Copeia, 2002 (1), 195-198 DOI: 10.1643/0045-8511(2002)002[0195:DBOCAP]2.0.CO;2

D. B. Means (2010). Blocked-flight aggressive behavior in snakes IRCF Reptiles and Amphibians, 17 (2)

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