Worm Grunting A Mystery Solved
It may not rank as one of the great scientific mysteries of all time, but the riddle of worm grunting has been solved, apparently.
Worm grunting, also known as worm fiddling or charming, involves driving a wooden stake into the ground and rubbing the top of it with a leaf spring or other flat piece of steel to make a grunting or snoring noise. Done in the right place under the right conditions, the result will be hundreds earthworms appearing on the surface of the ground. Worm grunting is practiced in parts of the southeast to obtain fish bait.
The mystery has been why the vibrations should cause worms to come to the surface. Kenneth C. Catania of Vanderbilt University has provided an answer: worm grunting mimics the sound of a predator, the eastern American mole, causing the worms to flee topside.
Dr. Catania is a neuroscientist who studies the senses, particularly the exquisite touch sense of the star-nosed mole. In work on moles, though, “there are a lot of little side tendrils of interesting ecology that goes on,” he said. “This is one of those.”
Dr. Catania worked with a worm-grunting couple, Gary and Audrey Revell, who own a bait shop in the Florida Panhandle. He found that the eastern American mole was endemic to the area, and that the moles consumed large quantities of worms. He also measured the frequencies of the vibrations as they dig and move around in the soil. The frequencies of worm grunting, while not a precise match, “reasonably overlapped” with those created by the moles, he said. His findings are published in the online open-access journal PLoS ONE.
He tested other hypotheses, including the idea that rather than mimicking moles, the vibrations match those caused by heavy rain hitting soil. Some worm species are known to surface after a downpour, but Dr. Catania found that the species he was studying was largely unaffected by rain.
Over all, Dr. Catania said, the work suggests that the worms are responding to what are perceived to be moles. And it’s a very strong response. “They come out of the soil as if they are running,” he said. “That is, if an earthworm could run.”
By HENRY FOUNTAIN
Published: October 17, 2008