Garden worm.

[Insomniak]

Hi,

So I was digging my garden and have come across lots of "tied up" worms like this one.
I admit to having no clue why, can someone enlighten me please?

I found them mostly in the dampest part of the garden where the drainage is poor.

[mbaldw]

Very interesting! I've heard it said that worms may tie a knot in themselves in a bid to make it more difficult for predators to eat them. Sadly I've never been able to establish if there's any grounding to this 'theory' -- to my mind it has terrific potential to go wrong for the worm! -- or whether it's simply an old wives tale. If it were true, I'd expect the worm to relax a little when whatever it considered to be dangerous had passed. Did you watch to see if they un-tied themselves when they thought you'd gone?

Cheers,
Marc.

[Insomniak]

I really should have watched them closely, shouldn't I?

All I can add is that for at least 5 or 6 mins they remained tied up.
At a guess, they were about 6 inches under ground and firmly tied up when I dug them up. There were plenty of those ground lover centipedes around (Haplophilus subterraneus, and yes, I had to look that up!) but I think they prefer roots to worms?

So, in an effort to solve this, I've just re-dug the damp part of the garden and found not even ONE tied up worm.
Plenty of healthy large ones and even more smaller thinner ones, though.
The ground is just as damp, we've had heavy rain almost every day.
I really wondered if it was a reaction to being in such wet conditions, but obviously not.

Fid

[mbaldw]

Hi Fid,

>>I really should have watched them closely, shouldn't I?

Heh, hindsight is a wonderful thing isn't it?!

>>At a guess, they were about 6 inches under ground and firmly tied up when I dug them up. There were plenty of those ground lover centipedes around (Haplophilus subterraneus, and yes, I had to look that up!) but I think they prefer roots to worms?<<

I've not been able to find anything on the diet of Haplophilus subterraneus much more specific than: "Nibbles plant roots and eats small subterranean animals." None of the references I have to hand elaborate on what the "small subterranean animals" are, although the south London wildlife charity Roots & Shoots have a record on their website of this critter feeding on a woodlouse during December 2001. I guess that their diet could conceivably include earthworms too. Regardless, there are plenty of other soil-dwelling critters that would eat a worm: Moles, beetles, flatworms, slugs etc.

>>So, in an effort to solve this, I've just re-dug the damp part of the garden and found not even ONE tied up worm. Plenty of healthy large ones and even more smaller thinner ones, though. The ground is just as damp, we've had heavy rain almost every day. I really wondered if it was a reaction to being in such wet conditions, but obviously not.<<

Well, at least you've got a little closer to the answer - you know one factor that isn't a cause. If the knotting behaviour is an antipredator manoeuvre (and I remain to be convinced), then it's possible that the worm was 'spooked' by something other than your fork. When you re-dug the soil today, maybe whatever (predator, perhaps) had caused the initial reaction had gone.

Another (admittedly very unlikely) possibility is aestivation - I found one website that says: "When the weather gets cold and the soil starts to freeze, earthworms move deeper down and overwinter in a state called aestivation. To aestivate, the earthworm generates a natural antifreeze and then curls up in a little knot." Has it been particularly cold where you are?

Cheers,
Marc.

[Insomniak]

This is intriguing!
I can safely imagine that little centipede nibbling on dead or dying animals as well as roots, but not on a living worm?
Well, I'm very open to correction on that!

On the original dig, I disturbed maybe 10 or 12 such knotted worms in an area of about 2 square metres.
That particular patch of ground had not been dug for several years.
Could that have a bearing on it? While it was as wet as the first time, the soil was in no way as compacted today. If anything, *that* might be a key factor.

As to the aestivation, a good point, indeed.
Though my understanding of aestivation was that it was a hibernation-like state induced to deal with *heat* rather than cold, and as such, something that would be likely in summer.
So... that IS a really good possibility.

Our weather was warm and more rainy than usual (even) for an Irish summer, I think our June broke some record for rainfall this year!
Right now, it's still rainy, but cooler.


And...from the same site you were on:
"Earthworms also aestivate when conditions become dry or hot."
Now if it had said "hot and wet", I would be happier!

Are we on the right trail?

Fid

[mbaldw]

>>I can safely imagine that little centipede nibbling on dead or dying animals as well as roots, but not on a living worm? Well, I'm very open to correction on that!<<

Well, I'm far from an expert on this, but my understanding is that centipedes (some species at least) are active predators.

>>On the original dig, I disturbed maybe 10 or 12 such knotted worms in an area of about 2 square metres. That particular patch of ground had not been dug for several years. Could that have a bearing on it? While it was as wet as the first time, the soil was in no way as compacted today. If anything, *that* might be a key factor.<<

Possibly. I've only ever come across the aestivation and anti-predator hypotheses for knotted worms.

>>As to the aestivation, a good point, indeed. Though my understanding of aestivation was that it was a hibernation-like state induced to deal with *heat* rather than cold, and as such, something that would be likely in summer. So... that IS a really good possibility.<<

You're correct, aestivation is technically a tactic to avoid heat/drought (from the Latin aestas, meaning "summer"). The website should've said (assuming there are the accompanying physiological changes) that they hibernate during cold winters and aestivate during hot/dry summers. In this case it could be aestivation; although, as you say, the conditions when you dug the worms up were pretty moist and June had been a very wet month. Maybe you should try e-mailing the Worm Research Centre and see if they've come across knotted worms before.

Good luck!
Cheers,
Marc.

[Insomniak]

Hi again,

I'll follow this up next week, I'm away from now until Tuesday next.
Maybe you'll dig up some more info in the meantime!

Fid

[naturegirl]

I have dug up 'knotted' worms many times and I think it is because of extremes in weather. When I have dug up most 'knotted' worms it has always been winter/spring time and in compacted soil, (we are on Kent clay here).

Hope this helps.

Naturegirl