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Sunday, October 26, 2008 | Science : Evolution and Biology | print version Print | Comments |

Document Secrets of worm grunting support Darwin's instincts after 127 years

by Lewis Smith, Times Online

Thanks to Paul S. Jenkins for the link.

Reposted from:
http://timesonline.typepad.com/environment/2008/10/secrets-of-worm.html

The secret of worm grunting, a mysterious technique used by fishermen to tempt worms to the surface, has been unearthed.

Worm grunting is popular in the United States - they even hold grunting festivals - and involves driving a wooden stake into the ground and rubbing it repeatedly with a length of steel.

To most people such behaviour might be regarded as, at best, eccentric but to fishermen it is a tried and tested means of providing enough bait to keep them going for hours.
A biologist intrigued by the practice has now established that the apparently suicidal behaviour of the worms in coming to the surface, where they are easy prey, is driven by a desperate desire to escape their deadliest of enemies - moles.

Moles are such voratious eaters of earthworms that the invertebrates would rather risk being caught by a bird or dried up by the sun than come within range of one.

Dr Ken Catania, of Vanderbilt University in the US, found that the vibrations created in the soil by rubbing steel on the stake mimicked those made by moles digging through the soil.

Fishermen had happily made use of the practice, known variously as worm grunting, tickling, snoring or charming depending on where it is done, but didn’t know why it worked.

His conclusion, reached after a series of experiments in the Apalachicola National Forest, in Florida, confirmed a remark made by Charles Darwin in his 1881 book The Formation of Vegetable Mould.

“It has often been said that if the ground is beaten or otherwise made to tremble, worms believe that they are pursued by a mole and leave their burrows,” he wrote.

Dr Catania, reported his findings in the online journal PLoS ONE, after carrying out a series of experiments in Apalachicola National Forest in Florida where eastern American moles, Scalopus aquaticus linnaeus, are plentiful.

He said: “Eastern moles don’t come to the surface when they are foraging, so fleeing to the surface provides the worms both immediate safety and the most efficient means for getting away from them.

“The moles are quite noisy. Often you can hear the sounds of a mole digging in the wild from a few feet away.”

The finding supports observation of gulls and wood turtles which have suggested the animals knew that by slapping their feet on the ground they would bring worms within reach.

He found, with the help of veteran worm grunters Gary and Audrey Revell, that hundreds of earthworms came to the surface within 12 metres of the stake.

“This makes it possible for an experienced worm grunter to collect thousands of worms in a day,” he added.

Comments 1 - 21 of 21 |

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1. Comment #271808 by aprocess on October 26, 2008 at 3:37 pm

In Britain, blackbirds pat their feet on the ground, possibly to simulate rain and the worms come up so they don't drown. It's what I was taught when I was a kid so it could be wrong :)

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2. Comment #271815 by ficklefiend on October 26, 2008 at 3:47 pm

 avatarYeah, that's what I was always told the seagulls were doing. We used to get them up by pouring soapy water onto the ground.

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3. Comment #271816 by PaulJ on October 26, 2008 at 3:48 pm

 avatar
The secret of worm grunting, a mysterious technique used by fishermen to tempt worms to the surface, has been unearthed.
unearthed - geddit? Ha ha.

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4. Comment #271825 by tvictor on October 26, 2008 at 3:53 pm

 avatar"Worm grunting is popular in the United States - they even hold grunting festivals - and involves driving a wooden stake into the ground and rubbing it repeatedly with a length of steel."

Now that's an interesting hobby

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5. Comment #271833 by gazzaofbath on October 26, 2008 at 3:59 pm

 avatarI hope the final work of Darwin on earthworms and vegetable mould gets a lot of prominence in the 2009 celebrations of Darwins birth (and Origin of Species publication) as it just shows very simpy what a fine methodical scientist he was. Even on a problem that although very significant many would have considered mundane.

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6. Comment #271862 by black wolf on October 26, 2008 at 4:37 pm

 avatarInteresting, I always thought they were emulating the pattering of rain on the surface to trigger instincts that would avoid drowning. I don't know how long an earthworm can survive under water though.
A few things to nitpick, I don't think the worms 'decide' to 'risk' anything. Either they have an evolutionary instinct that saves them, or I am gravely mistaken and the nervous system of a worm is capable of making conscious decisions.
I usually don't care about such usage of language, but experience shows that certain people will quotemine and twist any poetic, flowery, or even honestly humble choice of words just to get in a cheap shot at the ToE or Darwin. To any modestly educated person it is easy to see through such transparent trickery, but the ignorant followers probably won't, willfully or unwittingly.

edit: as an afterthought, it is not improbable that the same instinct avoids both drowning and falling prey to moles, if it reacts to incidentally similar ground vibrations or covers a range of them.

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7. Comment #271882 by bluebird on October 26, 2008 at 5:25 pm

 avatarGood article--saw it the other day on Discover.com magazine.

'Worm Grunting Festival'?!? I'll be dogged, there is such a thing:http://www.wakullacounty.org/worm_festival.htm

Hmmmmm...worms...fishing...'Crawdad Song'!
http://www.youtube.com/watch?v=BFPSKB99Anw

I enjoy Bluegrass music; still, H.B.D. to Strauss Jr, Bizet, Scarlatti, & Paganini!

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8. Comment #271888 by Planeten Paultje on October 26, 2008 at 5:35 pm

 avatarI see gulls (and sometimes crows) do the patting all the time, so it probably works.

I have also seen farmers use a metal strip with a wooden handle, about 50 cm long, attached to a long, thin, single electricity cord. Drive the strip into the ground and connect the cord to the hot outlet of an unprotected mains connector. The worms will race to the surface in their hundreds.

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9. Comment #271922 by Mango on October 26, 2008 at 6:45 pm

 avatarVoratious? Sounds right to the ears, but I'd still recommend he use a spell checker.

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10. Comment #271931 by Dhamma on October 26, 2008 at 7:07 pm

 avatartvictor: Ha - I love original people, and going to a festival where everyone shares a passion for worm grunting must be the peak of insanity!

I'd probably have a ball watching people getting excited over how well someone drives a stake in the ground! Hilarious people that make it worthwhile living.

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11. Comment #272044 by rod-the-farmer on October 26, 2008 at 11:31 pm

 avatarI don't remember there being any mention of moles and their appetites, but I DO remember taking history classes wherein we learned about the Diet of Worms.

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12. Comment #272048 by King of NH on October 26, 2008 at 11:38 pm

 avatar
tvictor: Ha - I love original people, and going to a festival where everyone shares a passion for worm grunting must be the peak of insanity!


Dhamma, if you're ever near the east coast, simply get off on any I-95 exit south of the Carolinas and north of Miami and you are certain to find these festivals around Labor Day. I knew my residence in Georgia would be short lived when I saw a giant catfish driving a police car around gas stations to lure tourists to the party. Funny if you don't live there, scary if you do.

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13. Comment #272119 by Christopher Davis on October 27, 2008 at 2:36 am

 avatarficklefiend, I used to use soapy water too...when I was a kid. I'd forgotten about that until you posted it. Any idea why it works'

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14. Comment #272296 by clatz on October 27, 2008 at 7:55 am

 avatarI am a bit gutted I didn't find this out through Ray Mears.

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15. Comment #272480 by danhayes on October 27, 2008 at 1:39 pm

 avatarI witnessed a seagull doing this just last week. I was wondering why it was hitting the soil until it started eating worm after worm...absolutely fascinating.

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16. Comment #272521 by MedMonkey on October 27, 2008 at 2:23 pm

 avatarThat Darwin guy must've been kinda smart, eh?

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17. Comment #272528 by perkyjay on October 27, 2008 at 2:30 pm

RE COMMENT #1 by Aprocess: What you learned in the UK as a child must be true, because here in British Columbia the robins and crows do exactly the same thing to attract the worms to the surface.

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18. Comment #272531 by Dhamma on October 27, 2008 at 2:33 pm

 avatarKing of NH: At least you had the joy(?) of actually witnessing it!

I'd love to go, but as I'm a European I'm rarely in the USA. Maybe it's worth going for this sole cause?

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19. Comment #272614 by chuckgoecke on October 27, 2008 at 4:31 pm

 avatar

5. Comment #271833 by gazzaofbath on October 26, 2008 at 3:59 pm:
I hope the final work of Darwin on earthworms and vegetable mould gets a lot of prominence in the 2009 celebrations of Darwin's birth (and Origin of Species publication) as it just shows very simpy what a fine methodical scientist he was. Even on a problem that although very significant many would have considered mundane.


I'll second this! This sounds like an interesting article. I don't think I would use the term "mundane" for any good science research. It is obviously not mundane to the scientist doing the research, and he or she would know best, being their area of expertise. The appearence of lack of excitement or significance is often just that it is ahead of its time, or the way it leads to other discoveries.

This book by Darwin sounds great, and probably ahead of its time, if vegetable mould was the term for compost at the time. I've often thought that Rodale was the grandfather of Organic Gardening back in the late 1930's(at least in the USA), but perhaps he was just building on Darwin... he would not be the first.

edit: Sir Albert Howard was probably the real grandfather of Organic Farming, bringing techniques from India in the 20's. Darwin was ahead of them both.

Other Comments by chuckgoecke

20. Comment #273081 by gcdavis on October 28, 2008 at 5:18 am

 avatarI have to admit to being a lapsed angler!

But when I was a kid, on the advice of some angling pundit or other, I used to empty a bucket of water mixed with a lot of washing up liquid onto the grass. After a while a few "irritated" worms would emerge, I then bathed them in a saucer of milk to restore their mucus. I am not kidding, it sounds quite daft now but what the hell!

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21. Comment #273298 by Apeseed on October 28, 2008 at 1:37 pm

 avatarAs to the explanation of noises simulating rain on the surface; I remember as kids we were playing a game of ring-around-the-roses or suchlike and after ten minutes or so loads of earthworms came to the surface. We all thought we had magically made them appear. We started calling it the worm dance ala the rain dance of American-Indians.
When I told my uncle about it he explained it as the worms reacting to the vibration as they would to rain.

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