For generations, Southern practitioners of “worm-grunting” or “worm-fiddling” have coaxed large fishing worms above ground by making vibrating sounds rubbing steel bars on wooden stakes that are driven into the earth.
Most never questioned why the system worked. They just were glad it did.
New research reveals that for decades, backwoods worm-grunters have actually been tricking the lowly earthworm into thinking it was being chased by its primary predator, and that’s why they appear above the ground–almost like magic.
After extensive research performed in northern Florida earlier this year, Vanderbilt University biological sciences professor Ken Catania concluded that the vibrations made by the “grunters” who rub steel bars over wood stakes actually mimic the sound produced by digging moles. In reaction, the worms quickly crawl from their burrows to escape their approaching natural predators.
Practiced historically and passed down among generations of worm-gatherers in the South, the custom is colloquially referred to as “grunting” because the of sound made by rubbing metal on wood, or “fiddling,” in reference to the physical motion that resembles pulling a bow over the strings of a violin.
Despite a lot of speculation, generations of worm grunters were never really certain exactly why the technique works—just that it brings the very large (and desirable) earthworm Dipocardia mississippiensis to the surface by the hundreds so they can be collected and used (or sold) as bait.
Biologist Catania, whose specialty is studying moles, first thought that the explanation behind the phenomenon was contained in a theory put forth by geneticist Charles Darwin, who once said, “If the ground is beaten or otherwise made to tremble, worms will believe that they are pursued by a mole and leave their burrows.” To investigate Darwin’s concept, Catania traveled to the Florida Panhandle this spring and enlisted the help of noted worm grunters Gary and Audrey Revell.
During his study, Catania actually recorded the vibrating sounds made by burrowing moles and compared them to the sounds produced by the worm grunters. Analyzing geophone recordings of the two types of sound, he found that the worm grunting vibrations were more uniform and concentrated near 80- hertz, whereas the moles produce a wider range of vibrations that peak at around 200-hertz.
“The moles are quite noisy,” Catania said. “Often you can hear the sounds of a mole digging in the wild from a few feet away,” he said.
Whether it’s called fiddling, grunting (or even snoring or charming), the technique is still used in certain parts of the southeastern U.S. today, though it probably reached its peak during the 1960’s in Florida’s Apalachicola National Forest. At that time, hundreds of commercial gatherers grunted for worms before the U.S. Forest Service began requiring permits for the previously unregulated practice out of concern that the industry was impacting the native worm population.
“This is a fascinating biology story and a fascinating sociology story,” said Catania, whose extensive study and findings were recently published in the scientific journal PLoS ONE. “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.”