Wednesday, June 5, 2013

It Depends on Your Point of View: “A Water Moccasin Tried to Get in My Boat” (Guest Post)

    Besides the myth that Cottonmouths (Agkistrodon piscivorus, on right) bask in trees along waterways and plop into boats and the unfounded legend that Cottonmouths are aggressive and attack people, the next most common misconception about the Cottonmouth is that they try to “get into” boats. At first glance this may appear to be a variant of the “falling into boats” myth, but that legend is very easy to explain away due to the behavior of non-venomous watersnakes (genus Nerodia). Non-venomous watersnakes frequently bask in trees and can be observed plunking into the water, which probably spawned the legend. Cottonmouths very rarely do this. I’ll even grant you the possibility that a non-venomous watersnake may indeed plop into your boat if you spend time along the water’s edge, although they usually fall into the water well before you get near them. I know this because I’ve been canoeing Southern streams since I was a little boy.

    So, what to make of this other legend, which I’ve heard so often? The story maintains that Cottonmouths swim right for you, and try to crawl from the water and get into your boat, presumably to attack you. Again, I’ve been canoeing swamps and rivers in the South my whole life, and this has never happened to me. I’ve also studied Cottonmouth behavior for nearly a decade, and during some of that time I used a canoe as transportation through my study site. In all cases of close encounters, the snake was not coming toward me. Sometimes Cottonmouths would be swimming close by, and once a snake even popped its mouth open at me in a “gaping” display as it drifted past in the current. But I was in its realm and it just happened to be there. Had I been a less experienced fisherman, would I have thought I was under attack, and that the Cottonmouth was trying to get in my boat? Maybe, but because these stories converge on a common theme, I suspect that the story is an urban legend, and it probably happens much less frequently than most people think, if ever.
    Another possibility is that non-venomous watersnakes may see boats and assume they are a big log, and try to crawl on top to bask. This explanation gives the legend an element of plausibility, which most urban legends need to persist. I admit this explanation is plausible, and I admit it’s even possible a Cottonmouth might do this, although both watersnakes and Cottonmouths are extremely wary animals that would be much more likely to bolt at the first sight of a human or a boat. But again, from the point of view of the snake, it is not trying to attack you, but instead trying to get out of the water for awhile. My guess is that if this happened to you and you gently prodded the snake with a paddle it would cruise away peacefully. But most people who tell this story say that the snake aggressively attacked the boat despite frantic attempts to dissuade them with all manner of improvised weapons (paddles, fishing rods, shotguns).
    I offer my own observation of a snake that “tried to get in my boat” which may help explain the legend. I was canoeing the Flint River in Georgia, within the known range of the Cottonmouth. I observed a non-venomous Yellow-bellied Watersnake (Nerodia erythrogaster, on right) cruising rhythmically along the bank of the river. These snakes are fairly large, have a nasty temper, and can spread their head wide, which makes it look “diamond-shaped,” so they are frequently misidentified as Cottonmouths . It was tongue-flicking frequently, and slowly and purposefully undulating along the water’s edge among the roots of the undercut bank. This cruising behavior has been described in many snake species, including the Cottonmouth. They sometimes cruise parallel to the edge of some natural feature, such as the edge of a pond, or the bank of a river. A brief video of a misidentified “water moccasin” exhibiting this behavior can be seen here. Notice this snake cruising along manmade structures. If there was a boat nearby, it would likely continue foraging along its edge. A brief video and still shots of a Cottonmouth exhibiting this behavior can be seen here. This is an active foraging style used by snakes to hunt frogs and other prey, because many creatures congregate at the water’s edge. After a few minutes observing the Yellow-bellied Watersnake hunt, I decided on an experiment.

    I paddled upstream a ways from where the Yellow-belly was cruising, and stationed my canoe parallel to the bank. If it continued upstream on its present course, the snake would “come right for me.” If I was a fisherman—who often place their john boats along the water’s edge in a similar fashion—I would be “minding my own business fishing.” I waited about 20 seconds before the “water moccasin emerged from nowhere” and “came right up to my boat.” The snake then swam along the edge of the canoe, using it (instead of the bank) as its foraging path. Or, according to the legend, it “tried to get into my boat and attack me.” At the last moment, I reached down and grabbed the snake by the midsection and captured it. I had invented a new strategy to capture these quick non-venomous snakes, and had simultaneously debunked a classic Southern legend.

Sean Graham is a post doctoral researcher at Penn State University. He received his PhD from Auburn University in the same lab as David Steen. His Master’s and PhD research focused on the behavior, reproductive physiology, and immunology of the Cottonmouth. He welcomes you to share your Cottonmouth stories in the Comments below.

Want To Learn More? Check Out These Scientific Articles:

S.P. Graham (2013). How frequently do Cottonmouths bask in Trees? Journal of Herpetology

B.C. Savitzky (1992). Laboratory Studies in an Opportunistic Pitiviper, the Cottonmouth, Agkistrodon piscivorus Biology of the Pitvipers, 347-368

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