Moles, not magic, make worm 'grunting' work

June 12, 2009 By BRENDAN FARRINGTON , Associated Press Writer

(AP) -- Gary Revell gets up every morning before sunrise, heads into the woods and grunts. Not because it's so early. It's the term for coaxing worms from the ground by the hundreds to be scooped up and plopped in a tin can until he can sell them for fishing bait.

He pounds a two-foot wooden "stob" or stake into the earth and rubs it with a 10-pound piece of flat iron. The vibration or "grunting" causes worms to panic, and they wriggle from the ground. For years it was just a guess why.

Vanderbilt University professor Ken Catania wanted to expand on a theory put forth by Charles Darwin that worms may sense moles are pursuing them if the ground trembles.

He joined Revell and his wife, Audrey, on a recent expedition and concluded that when Revell rubs the stob, worms do indeed sense that the predators are digging through the earth to eat them. The worms hightail it to the surface, only to be scooped up by Revell for fish food instead.

"Ken calls me the giant mole-man," Revell said with a laugh as he carried his equipment deep into Tate's Hell State Forest. "All I'm doing is mimicking the mole but in a larger scale, you know what I'm saying? That's how come they come up in a large area."

On a recent day, Revell, who has been scooping up worms for some 50 years, was out with two other grunters as the first light filtered through Tate's Hell. The only sounds were crickets chirping, woodpeckers pecking, birds singing and mosquitoes and horse flies buzzing - until Revell got to work.

The loud sound of metal pounding wood was followed by a steady, grunting rhythm as Revell got on his padded knees and began rubbing the stob. Almost immediately, worms starting to come up.

"They look good!" Revell yelled to his partners, clearly taking pride in his work. "Boy, that's pretty bait. Makes me want to go fishing."

For a good three yards around Revell, the ground was crawling and the other grunters were busy picking up worms.

"Oh yeah, it's magic," Revell said during a break. "There's an art to it. I've tried to teach people how to do it, and they just give up. You have to be really determined. It's got to be in your blood."

Some of the "magic" might be that the sound of the stob's vibration is strikingly similar to a recording of a mole digging, Catania said. He stuck a microphone in the ground to record the noise the stob makes and also measured how fast worms crawled away after reaching the surface.

"It seemed like they were scared of something as they came up sort of rushing, for a worm, out of the ground," Catania said.

The Revells are what the worms would consider a "rare enemy," according to Cantania's study.

"Coming out of the ground is not the smartest thing for a worm to do," said Catania. "In some areas it's really hot and dry, and there's predators out there - we saw them get attacked by ants and snakes and lizards now and then. Why would they do that?"

He believes it's because for millions of years, moles have been eating worms, and they've developed an escape instinct when they sense the predators are burrowing nearby.

The Revells, whose main source of income is selling the worms he gathers, work the Apalachicola National Forest, which covers nearly 600,000 acres southwest of Tallahassee, and Tate's Hell, immediately to the south.

Before meeting the couple, Catania had never witnessed the practice.

"It's amazing to me, there's nothing like going to see it. I thought it was incredible," Catania said

Later, while sipping iced tea at the Revells' home, he put a mole into a bucket filled with dirt and worms.

"It was amazing, man," Revell said. "When he dropped that mole in that bucket of worms, it was just like fear was in them. They come out of that ground, right out of that bucket. That pretty much let him know what he wanted to know about them. It was a predator/prey like thing."

Catania repeated the experiment under more controlled conditions, filling a container with dirt and a specific number of worms, waiting until they were all settled under the surface, and then letting a mole loose through a tube at the bottom of the container. The worms soon began fleeing out the top as fast as they could.

He also filled a much larger container with worms and ran a water sprinkler over it, simulating rain. The didn't rush out. That helped disprove the theory Revell has long had about why grunting works.

"This particular study was just wonderful because each little step made so much sense," Catania said. "It just all sort of fit together one piece after another all stemming from that original thought Darwin had."

©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Explore further: Florida's 'Worm Grunters' Collect Bait Worms By Inadvertently Imitating Mole Sounds

Related Stories

Zombie worms found in Britain's North Sea

October 19, 2005

So-called zombie worms that feed on bones of dead whales have reportedly been found in England's North Sea. Scientists say the worms belong to a new class of marine organism that scavenges whale carcasses, The Independent ...

Marsh-dwelling mole gives new meaning to the term 'fast food'

February 7, 2005

The star-nosed mole gives a whole new meaning to the term "fast food." A study published this week in the journal Nature reveals that this mysterious mole has moves that can put the best magician to shame: The energetic burrower ...

Study connects obesity with nervous system

January 23, 2008

A discovery by Queen’s biologists and their students sheds new light on the genetic roots of obesity – a condition that is increasing dramatically in North America and has been linked to heart disease, diabetes and some ...

Recommended for you

Scientists shed light on biological roots of individuality

February 16, 2018

Put 50 newborn worms in 50 separate containers, and they'll all start looking for food at roughly the same time. Like members of other species, microscopic C. elegans roundworms tend to act like other individuals their own ...

Plants are given a new family tree

February 16, 2018

A new genealogy of plant evolution, led by researchers at the University of Bristol, shows that the first plants to conquer land were a complex species, challenging long-held assumptions about plant evolution.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Jun 13, 2009
awesome !!!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.