The researchers created 1,200 life-size models of coral and scarlet king snakes out of plasticine, a mixture of wax and modeling clay and placed the copies in the wild, both within the coral snake's natural range in the southeastern United States and north of that range in central North Carolina, where they are absent. The biologists reasoned that if mimicry were causing the king snake to resemble the coral snake, predators would be more likely to attack the former where coral snakes are not found.
And that's just what their experiments showed. Because the plasticine models retained bite and scratch marks, they became a clear record of how often predators grabbed them.
"Attacks were much more frequent on our ringed models in central North Carolina than they were in southern North Carolina and South Carolina, about 50 percent vs. about 6 percent," Pfennig said. "Various predators readily attacked our model scarlet king snakes but only where no coral snakes lived."
The UNC team also conducted comparable experiments in Arizona with the same results, Pfennig said. Controls were fake "snakes" bearing either stripes rather than rings or plain brown skin. "These are very exciting results because they show how very strong natural selection is even in areas that are not so far away from each other," the scientist said.
Bates made his original observations about mimicry's effects on natural selection on similarly appearing butterflies, some of which were toxic to birds while others were not, he said.
"You can get resemblances between species that have nothing to do with mimicry," Pfennig said. "Sharks and dolphins look very much
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Contact: David Williamson
david_williamson@unc.edu
919-962-8596
University of North Carolina at Chapel Hill
13-Mar-2001