Grunting Scares Up Worms
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.
When biologist Ken Catania, an associate professor of biological sciences at Vanderbilt University who studies moles, heard about the peculiar practice of worm grunting practiced in the Apalachicola National Forest in the Florida Panhandle, one of his first thoughts was an observation made by Charles Darwin. "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," Darwin once remarked. So, this spring Catania 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, was reported in the October 14th issue of the Public Library of Science ONE.
In his preliminary research Catania found some other interesting clues. One was the observation by the famous Dutch ethologist Nikolaas Tinbergen that one species of gull performs a "foot paddling behavior" that appears to bring up earthworms to the surface, a response he attributed to an innate reaction that enables the worms "to escape their arch enemy the mole. …