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

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

[david]

"... If anything I would have thought this seems to disprove Darwin's theory of evolution in that by now worms would have learned of this threat and found a way to transform themselves to avoid this obvious threat to their existence."
And for how many millions of years have worms been 'learning' about this threat? 'Transform themselves'? Suggest actually reading Darwin before theorising.

[Spungey]

I thought moles harvested worms and any other invertebrates by regularly patrolling their extensive network of tunnels into which any unfortunate meal items had fallen. I don't think they actively dig after their prey.
Regarding Levon's post (06/01/09), I seem to remember the same argument arising with the evolution of the eye, which has subsequently long been explained, as has the bacterial flagellum, sometime in 2003...
http://www.youtube.com/watch?v=SdwTwNPyR9w&feature=related

[ericg]

forget digging them up, buy them from wormsonline.co.uk. perfect for fishing and home composting.

[adam]

Hello,

So would the same technique work here in the uk to catch worms or just USA because the moles are a diffrent type to ours?

[L Hayes]

I wish journalists would bother to either learn how to spell or spell check... as mentioned previously by George and others, the correct spelling is 'voracious'! It is not 'voratious'! It comes from 'voracity' not 'voratity'!

The worms can probably spell better.

[GEORGE]

1. Voracious, with a c

2. Scalopus aquaticus; or
Scalopus aquaticus (Linnaeus); but not Scalopus aquaticus linnaeus.

[catherine holland]

Worms don't 'believe' anything, they act instinctively. Another waste of time and money. Plus people did not think the Earth was flat, these stupid ideas have been put around by 'scientists' with closed minds and full wallets. The Old Testament tells us that God 'sits enthroned above the circle of the Earth'

[rich]

I understood that the worms come to the surface because the heavy pounding sounds like heavy rain, and they would surely drown if they didnt take such action.

[George Myers]

I heard an earthworm mystery: how did they get from Europe to North America? They weren't here before the last glaciation but appeared afterwards. Did very early settlers bring them or did they come over on big chunks of floating land? Early stowaways? The composting latrine of Viking ships? I think though there were always moles here in North America.

[Neal Miller]

Fascinating article.
My apologies for the idiots.

[Behr]

Some people feel it is necessary to show their ignorance of Natural Selection. If you took all the worms that humans collect by using this mathod for a year and compared it to 1 hour of mole hunting by all the moles the moles would win hands down. So worms are better off facing humans than moles. The effects of any adaptation for worms to stay underground would dissappear when eaten by moles.

[Kolti]

Soapy water, mild electric current and tapping a stick in the ground are all old ways of bringing a worm to the surface. The Yanks have another way.

They hold elections.

[wen]

Well done for this profound insight in to the life of worms in relation to this serious threat to their existence. If anything I would have thought this seems to disprove Darwin's theory of evolution in that by now worms would have learned of this threat and found a way to transform themselves to avoid this obvious threat to their existence.

[mi-mi-]

The real proof of Darwin's theories would be if the worms decided not to come to the surface anymore because they knew that they woule be caught, or better still decided to gang up on the grunters!

[Carey Rowland]

Thank you, Lewis for the fascinating article.
You Brits have certainly unearthed a fascinating controversy. I stand with Patrick's position on this one. The passage from Romans 1 is appropriate for all times, but especially our present age.
Furthermore, I must report that I do appreciate God gathering the wriggly little bastards to enrich my compost pile here in the mountains of North Carolina, USA. I wonder if he grunted; maybe he just called them by his Word.
Carey Rowland, author of Glass Chimera

[Ben]

Denis: You are conflating emotions with instincts. The two are very separate things and to do so is both dangerous and misleading.

"This also proves that worms can experience fear. Why else would they try to escape when their life is in danger? From observing both wild and domestic animals over the years I have formed the conclusion that fear is a very strong emotion experienced by all animals and is the reason why some animals will attack when in a state of fear. Jealousy is also a very strong emotion in the animal world!"

[graham seed]

Worms making for the surface to escape moles has been known for years.

Another waste of money and time funding a piece of useless academic research.

[Denis]

This also proves that worms can experience fear. Why else would they try to escape when their life is in danger? From observing both wild and domestic animals over the years I have formed the conclusion that fear is a very strong emotion experienced by all animals and is the reason why some animals will attack when in a state of fear. Jealousy is also a very strong emotion in the animal world!

[David]

How can we conceivably be having this discussion in 2009 ? Patrick, if you are going to design DNA for people, why would you leave the precursor genes in there common to all evolved species? Mike, the worms have two choices. Stay below and be et by a mole that they can hear or come up and be et by a bird that may or may not be there. Would you jump off a burning oil tanker despite the fact that you knew there were sharks in the water ? "wise man" Saddam already pretty much did that. http://architecture.about.com/cs/countriescultures/a/saddamspalace.htm. Anyway, doesn't it have to fall again ? (Revelations 18). Plus which, WTF does this have to do with worms ? Levon, thank you for your insightful contribution. Mr Pierson the worm is not committing suicide out of some existential disdain for a subterranean life but running from one predator despite the risk of the other. The point is that it does so without the benefit of a brain. Over time, the worms that did this survived in higher numbers, those that did not died in higher numbers. This worm grunting business will affect that trend, and if it went on long enough this trait will be bred out.

[Brian Donahue]

WORM DANCE
On one occasion I went to pick up a worm on warm walkway as it was drying out and as I touched it; it did a vertical sort of dance. This must be a natural defense to birds etc.

[C Pierson]

What are these "Darwinites" smoking? A worm capable of commiting suicide ? Seems a reality check is greatly in need by anyone agreeing with this premise. I apologize for being so blunt, but in this instance, it is most definitely justified.

[Mark Hulton]

This then suggest's that worms have a brain and have thought process ?

[tone]

worms can also be brought to the surface by a dilute solution of potassium permanganate, which is extremely effective for some reason. even watering the soil can cause them to emerge.

[Mike Collins]

The people of Nantwich in Cheshire have held a worm charming championship for many years (see www.wormcharming.com), so this is not exclusive to the USA

[R.Rees]

What a wonderful way of proving Darwin right Philip - the stupid fishermen that try your method will all be fried to extinction. The wise ones will just buy their bait and survive to breed.