"Herps of the Southeast" Virtual Walk
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21 —
Featured Herp
Cottonmouth
Florida
Caverns
State Park, FL
(Agkistrodon piscivorous)
Eastern Cottonmouth
(Agkistrodon piscivorous)
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Cowards, Bluffers, |
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| Our behavior was not entirely foolhardy, as we were wearing snake-proof boots (at least, that's what the label said). We were testing our theory that venomous snakes bite people only as a last resort--once they have determined that an easy escape is not possible or that the intruder cannot be held off by a threat display. The idea was put most succinctly in the 1950s by the late herpetologist Clifford Pope: "Snakes are first cowards, then bluffers, and last of all warriors." Our study was designed to determine at what point the warrior mode comes into play. We'd tested more than forty cottonmouths in the swamps and wetlands of South Carolina's Savannah River, and they had bitten only when stepped on or picked up. |
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After twenty seconds, Mike signaled and Whit nudged the snake harder with his boot.
It closed its mouth and attempted to escape by slithering partway into the water. Whit
placed his boot firmly on the rear half of its body, holding it on the
log. The snake turned back to face the boot and reopened its mouth but
still did not strike. Again twenty seconds elapsed. We could now detect
the unmistakable musk of an alarmed cottonmouth; some people say the smell
is like cucumbers. Only when Whit grasped the snake mid-body with a leather
glove had the cottonmouth finally had enough. The. fangs sank deep into
the glove, and venom dripped out of the animal's mouth. (The glove,
however, was not on Whit's hand but had been fitted onto the open end of a
pair of "snake tongs" some three and a half feet long.) About 10 percent of the snakes we've tested have bitten the boot after being stepped on, only 40 percent have struck when picked up with "the hand." Understanding how a cottonmouth protects itself requires adopting the point of view of a snake: What if you were only a couple of inches tall and a towering beast were approaching? Striking is a last resort. To begin with, by challenging a much larger enemy, the snake is potentially exposing itself to a great danger. It also needs to conserve its precious venom. Composed of complex proteins that require time and energy to produce, venom is vital for capturing prey. |
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When cottonmouths bite people
defensively, they often inject less venom than they have available. The
importance of conserving venom is indicated by laboratory studies showing a
high proportion of so-called dry bites, in which little or no venom is
injected. Experiments have demonstrated that venomous snakes can control the
amount of venom injected during a strike, using only what is necessary to
subdue prey. It would seem that natural selection should therefore favor
those snakes that use venom only as a last resort for defense. No reliable snakebite statistics are available to confirm the exact number of bites cottonmouths inflict each year, but the estimated numbers are much lower than for copperheads or rattlesnakes. In the United States, an average of fewer than ten people die each year from the bites of all native snakes. So far, our results show that we should not be so quick to indict cottonmouths as aggressive enemies prepared to attack. |
J. Whitfield Gibbons; a University of Georgia professor of ecology at the Savannah River Ecology Laboratory (SREL), is the author of Ecoviews: Snakes, Snails, and Environmental Tales (University of Alabama Press, 1998).
Michael E. Dorcas is an assistant professor of biology at Davidson College in North Carolina and the author of several journal articles and book chapters on herpetology.