Earthworms after rain (2019) | Hacker News Reader

Earthworms after rain (2019)

blog.nature.org

161 pointsthunderbong53 comments

> Many earthworm and soil experts have settled on a version of this explanation: Moving around the soil is relatively slow and difficult, even for earthworms. They can cover a lot more ground on the surface...when it rains, the surface is moist enough for worms to survive and remain hydrated. For a few species, they can more easily move about and find mates. For other earthworms, it may well just be a way to disperse and move into new territory.

Makes sense to me especially with other notes about the absence of young worms. And it feels like predators might be at least a little less active during the rain.

Anyway as a sucker who always helps a worm on the sidewalk out this article was super helpful :)

I always thought they went on the surface because they were drowning.

As the article states: earthworms breathe through their skin; require moisture for this process; and do not have lungs that can fill with water.

In fact I have a home built aquaponics system and have worms in the grow beds. Because the oxygen content of the water stays pretty high, the earthworms do just fine submerged at all times.

fellow sidewalk worm helper here. ever since i was a kid, i could never bear the sight of earthworms on the side walk, getting stepped on or baked dry when the Sun comes out. i had always thought i was alone in this behavior (none of my friends did this), until i read that Albert Schweitzer did this too. he won the nobel peace prize in 1952.

> he won the nobel peace prize in 1952.

Though not due to saving earthworms I believe. ;)

It probably didn't hurt though. Maybe it clinched it for him when the committee found out.

I can’t argue with that. :)

> A tradition in the Appalachians and elsewhere, called worm grunting or fiddling, involves using a saw or stick to make vibrations on the soil’s surface. This brings worms to the top that are then harvested for bait. Essentially, humans are mimicking the sounds of hunting moles.

> (I admit I have tried this without much luck).

A true nerd - I thought about doing the same :)

I've seen this done successfully in the Ozark mountains of Arkansas. The way it was done was to saw off a small tree about 2 inches in diameter with a hand saw to leave a stump about a foot high. Pretty sure it was a dogwood or maybe a maple, though the type of tree probably isn't important. Then saw into the top of the stump. The ground was fairly damp at the time. Worms were coming out of the ground all over the place, probably a hundred or so. This was probably 40 years ago though, so my memory is pretty sketchy, maybe it only seemed like a hundred to 10 year old me. Plenty of worms though, more than enough for a day of fishing.

None of the three of you thought to check YouTube? :) https://youtu.be/3ILoGcSxCAY and https://youtu.be/fvmt2_uzsnQ

Get some worms: https://www.youtube.com/watch?v=I2-kfbjxKLc (How to make the Ultimate Electric Worm Getter!)

As others have mentioned electricity works, but so does a sledgehammer or a pole-pounder.

Do worms come to the surface because of the water, or because of the thunder?

Beginners guide to starting a worm farm - to aid in composting or to get their casings (they move their poo above ground) - electricity or strong localized vibrations.

Probably off topic, sorry.

I've been a backyard composter for years, and have been thinking about trying out the worm beds too. One of the local hardware stores specializes in homesteading, and they have "the worm guy" come in once a week. One item available is gallon jugs of a brownish watery liquid that not only acts as a fertilizer but also has earthworm eggs. I used this on my freshly built raised beds. Earthworms galore!

Same store also carries packages of ladybugs to help with aphid control. Fun store

Birds stomp or trembling their feet to get worms to come up.

Here’s an article on it: https://www.geographyrealm.com/the-foot-trembling-bird-gets-...

And videos of birds doing it: https://www.google.com/search?q=bird+(stomping+OR+trembling)...

Interesting to consider that

* a bird might be mimicking the rainfall to drive the worms out

* the worms might be triggered to excavate during rainfall if they believe that predators are approaching

Seems kinda circular

Fun fact: In German, earthworms are called rainworms.

In Polish, earthworms are "dżdżownica" which is derived from old Slavic for rain.

Yet again, I'm jealous of the potential Scrabble scores Polish has over English

In Swedish they are "daggmask" which translates literally as "dew-worm", so the moisture connection is clearly there, too. Fun!

Their behaviour to surface during rain and get maximum human attention likely to get them named after "rain" across cultures.

TLDR: To travel easier than by digging. The rain is required for moistness.

The article provides background for alternate, incorrect theories that might still interest you.

I thought myself of the "maybe they mean to move somewhere else and it's easier after rain" theory, but the follow up question was: where?

How does an earthworm decide where to go? Do they just pick a random direction, because statistically that is advantageous for the species?

I’m also curious about that question. I can’t imagine that the area they are in has been “picked clean”, so where are they going?

I would speculate that it allows them to expand their mating pool and increase bio-diversity.

I had read rom a fairly antiquated source that the acidity of our rainwater as it runs across the ground and into the worm burrows is quite high (or low?) for earthworms.

Supposedly, this drives a slightly delirious behaviour and results in earthworms getting a little lost and/or stranded, explaining some of the marooning that is often found in the aftermath of a heavy downpour.

As this article failed to mention any of the above, I assume this fanciful theory hasn't survived.

I never got any of these explanations in school (or if I did, I don’t recall). But I’ve wondered about it and my working theory all along has been that there’s an imperative advantage that’s worth the risk. I hadn’t thought of ease of movement (though that seems obvious to me now), just availability or viability of whatever else falls during a storm.

This phenomenon was one of the first ways I saw evidence of the different paces of evolution.

Some part of the worm says “it’s raining, it’s time to go”, but it has little to no concept of pavement, asphalt, buildings, and foot traffic and therefore much to it’s surprise the worm ends up drying out on what’s essentially a humongous desert.

In the timescales of the evolution of the earthworm, pavement just occurred yesterday.

Since humans began laying asphalt, I would assume that the earthworm has gone through more generations than humans.

if only evolution worked on generational time scales, who knows where humans might be now.

The only thing that is sad; earthworms are yet *another* vital cog in the ecosystem...

And when it rains, they come up and many die in gutters and concrete they crawl upon and cannot find dirt again.

Obv this is good for the Early Birds, but the worms are important for the soil..

(one thing humans havent really paid attention/cared about is what the blankets of concrete do to kill a healthy soil in an area...

---

Also, I am surpised nobody mentioned https://www.youtube.com/watch?v=wCDIYvFmgW8 <<-- The whole premise of DUNE

In North America, earthworms are an invasive species...

There are native worms. The red wigglers are introduced to the north but the natives would have migrated there eventually.

Right, but for thousands of years there was apparently no worm population. The plant composition changed significantly once worms became widespread. So they're beneficial in some cases, but not essential ecosystem cogs.

They don't live under ice. There were worms before the ice. It's not as big a deal as the doom trollers make it out to be. The earth has never been a static system.

> earthworms breathe through their skin and require moisture to do so.

The article would be greatly improved by removing this ineffective, unconvincing sentence, in addition to a couple of others. Requiring moisture in order to extract oxygen from the air is obviously not the same as being able to extract oxygen while fully submerged, if we think about O2 diffusing through a thin layer of water versus bulk. That's could be why rational people believe the classic hypothesis about earthworms surfacing to avoid drowning, even knowing that the critters are moist.

The next sentence talks about human lungs filling with water, but lungs are also moist.

(2019)

It always surprises me when a phenomenon so well-known turns out to be poorly understood.

Give it a couple hundred years. That can be said about all of the phenomena.

(And on top of that, most of what's called "understanding" is just citation of somebody else's understanding.)

I also felt that way until I got older and realized that “we know everything about this” is mainly a fantasy that makes it convenient to teach things to people in school.

In reality we actually understand very very little (if anything)

If I was a parasite infecting worms, I would try to make them surface to increase the spread. Maybe the water is a trigger and only adult worms come out to maximize the load.

in other earthworm news, I recently learned about the invasiveness of earthworms (in minnesota)

https://www.dnr.state.mn.us/invasives/terrestrialanimals/ear...

I didn't get theory of "worms come to the surface to escape predators", shouldn't they stay put instead?

Moles

Yea, but by coming to the surface they greatly increase the likelihood of attack from birds.

That risk can be greatly reduced by coming out when it's dark. I see lots of worms on the sidewalk at night after a rainy day...

TLDR: They can move faster above ground in the rain without dehydrating.

at the risk of being squashed

Being eaten by avian predators is probably a bigger risk. But apparently it’s worth it.

my highschool teacher explained this a long time ago. its interesting things resourface easy.

I kinda hate how everything is a blog post these days.... If something can be summed up in a couple paragraphs, then please do it. I understand it's about web and SEO but I still don't like it.

Old man yells at cloud, yeah yeah I know

You might have wanted twitter.com, it’s a wondrous place with many quick reads.

Earnest question - what is the length at which a not-blog-post becomes a blog post, and what's the name for the shorter-thing?

EDIT: I feel you, I'm also irritated at the drive to SEO - just not sure what naming you would apply to the shorter-thing.

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