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“Worm grunting involves going into the forest, driving a wooden stake into the ground and then rubbing the top of the stake with a long piece of steel called a rooping iron. This makes a peculiar grunting sound that drives nearby earthworms to the surface where they can be easily collected for fish bait.

Despite a lot of speculation, worm grunters don’t really know why the technique works. But Catania, an associate professor of biological sciences at Vanderbilt who studies moles, thought that the explanation might lie in Darwin’s remark: “It is often said that if the ground is beaten or otherwise made to tremble worms will believe that they are pursued by a mole and leave their burrows.” So this spring he traveled down to Florida and performed a number of experiments to test this hypothesis with the cooperation of veteran worm grunters Gary and Audrey Revell. His conclusion, that the humans are driving the worms to the surface by unknowingly mimicking the sound of digging moles, is reported in the Oct. 14 issue of the Public Library of Science.

“This is a fascinating biology story and a fascinating sociology story,” says Catania, who received the MacArthur genius award in 2006. “The biology story is the question of why the worms behave as they do and the sociology story is the fact that hundreds of people once made their livelihood by collecting worms in this unique fashion.”

Actually, the technique is practiced in a number of parts of the southeastern United States, under various names including worm fiddling, snoring and charming, but it reached its apex in the 1960’s in Apalachicola when thousands of people grunted for worms until the U.S. Forest Service began permitting the previously unregulated practice out of concern for the impact the industry was having on the native worm population. Now far fewer people practice this technique. The Revells are two of the few that still make much of their living from worm grunting.”