Look before you shoot
Snake Mistake – Feature
The sky is August-white, and the afternoon is baking hot, humid, downright gummy. No matter: You’re blissfully ensconced in your tube, floating down the Shenandoah—or the Rappahannock or the Maury or some sleepy creek—hugging the banks to take advantage of their occasional shade. Your beverage is still cold despite the heat of the sun, which beats on your thighs and arms, and you think about dropping through the tube’s hole and into the water. But then you pass under another cluster of overhanging branches, and the cooler air is a miracle. You sigh, tip your head back, close your eyes and drift … then oof! A writhing mass plops into your lap, it’s a snake—a water moccasin! Aaaaaaaaah!
Relax, Virginia. Unless that creek is in the southeastern part of the state, the Dismal Swamp in particular, your visitor is almost certainly the completely harmless brown water snake (Nerodia taxispilata) that’s found statewide, and not a water moccasin, a.k.a. cottonmouth, a.k.a. the semi-aquatic pit viper Agkistrodon piscivorus. It’s a common mix-up. So common, in fact, that one former naturalist for a southeastern park reported nearly 200 snakes that fishermen presented to him throughout two summers, proud of having killed the “evil, poisonous, venomous, aggressive, dastardly cottonmouths.” None of them—not one—was a cottonmouth; all were brown water snakes.
Sure, the two species are similar: Both are hefty and brown, and the cottonmouth’s markings vary too much to help distinguish them at a glance. Still, the differences are significant—if one dares get close enough to check. Between its eye and nostril, on each side of its face, the cottonmouth has the telltale heat-sensing “pit” that marks it as a pit viper. While the brown water snake has round pupils, the pupils of the moccasin are vertical and catlike. Easier to see is the shape of the head: Is it narrow, flowing into the body? Brown water snake. Or is it the wedge shape that marks poisonous snakes? There are also obvious differences of behavior. Brown water snakes do (excitingly!) enjoy basking high in a tree overhanging water, while cottonmouths prefer logs and rocks near water. When a cottonmouth swims, you can see most of its body undulating on the water’s surface, head poking up; the brown water snake swims underwater.
Perhaps the most obvious difference between the snakes is how they respond to disturbance. The brown water snake invariably skedaddles, whereas the cottonmouth curls up, rears its head back and opens its mouth wide, exposing that signature cottony-white maw: “Bring it on.”
That is the cottonmouth’s threat display, and that’s all it is—a display. In a recent study about how snakes respond to human encounters, University of Georgia herpetologist Whit Gibbons donned snake-proof boots and went to the swamp looking for any variety of the six venomous snakes native to the southeast (Virginia has three, including the copperhead and the timber rattlesnake, both found statewide): “I stand for 30 seconds beside the animal wherever it is found,” he writes. “Next I place my snake-proof boot lightly in the middle of its back, just enough to restrain it.” Of the “dozens” of cottonmouths he met this way, all made threat displays, and none bit the boot. The lesson? If you see a cottonmouth, simply move away.
Venom is biologically expensive to a snake—any used means less for the hunt—but they’ll use it if the threat doesn’t abate. People are bitten most often when trying to catch or kill a snake. Even then, fatalities are very rare: Think of the countless hunting dogs bitten each year. Very, very few of them perish.
In the unlikely event of a venomous snakebite, according to the Virginia Herpetological Society, the best thing to do is head for the ER. In the meantime, mark the bite site with a Sharpie, remove any rings or other constricting jewelry, have the person lie flat with feet raised, and apply a pressure bandage. Skip the tourniquet, which traps venom and may speed necrosis, and don’t even think about sucking it out by mouth or cutting out that chunk of flesh with your handy Bowie knife. You are not in a cowboy movie.
And if a brown water snake drops into your boat, don’t shoot. That would be serpentine logic indeed.
(Originally published in the August 2008 issue.)
