Ever wondered why you’ve popped outside after a rain to see earthworms sprawled across the pavement or lying in your garden like miniature casualties? While it’s a common sight, we probably don’t think too much about it since we probably learned as school kids that earthworms rise to the surface when it rains because they are drowning.
According to scientists, it gets a little more complicated than that.
Why do worms come out when it rains? Some kinds of worms need more oxygen which they can’t get when submerged by rainfall. Another reason that brings worms scrambling to the surface of your garden is that pattering raindrops sound like moles. Finally, earthworms need hydration, and rainfall makes it easier to navigate through fresh, damp soil from deep underground.
Why do worms come out when it rains? Let’s bust the myths and discover these top 3 reasons that affect why earthworms come out when it rains.
3 Reasons Why Worms Come Out When It Rains
1. They Need Some Fresh Air
Why do worms come out when it rains? According to The Scientific American, most earthworms can stay submerged in water for up to two weeks if they still have access to oxygen.
Why do worms come out when it rains and die? It’s because they’re trying not to die. While humans inhale air with their lungs, earthworms breathe through their “cuticle” or skin.
Oxygen penetrates the earthworm’s skin to head straight to its blood vessels.
When a worm drowns, it’s not quite the same as a human drowning, but that doesn’t mean that rain can’t flood an earthworm out.
Oxygen diffuses 1,000 times more slowly when it has to pass through water instead of air. When the soil floods, worms come up to get more air.
Why do earthworms come out when it rains? It all depends on the type of worm that lives in your garden.
For example, some earthworm species take in more oxygen during the night than in the daytime.
Other species absorb equal amounts of oxygen over the space of a day.
Why do earthworms come out during rain? According to research done by the University of Lancashire, worms that need more oxygen at night couldn’t handle a deluge of rainwater very well.
That’s because when these worms need more oxygen at night, it’s the same time that water is most likely to accumulate.
Some earthworm species don’t need as much oxygen, so they never come to the surface after rain.
Why do worms go on the road when it rains? While you might worry that your driveway or garden looks like a worm battlefield after the rain, it’s important to remember that only a small percentage of adult earthworms emerge.
Scientists have found no juvenile earthworms among the risen masses, so it’s safe to assume that they tolerate waterlogged conditions better than adults and that there’s plenty more where they come from.
2. They Think It’s Moles
Why do worms come out on pavement when it rains? Or why do earthworms come out during rainy season? Experts explain that the pattering raindrops can sound like their number one enemy, moles, approaching.
This vibration echoes through the soil as moles hunt for earthworms, so fleeing worms end up above ground.
It’s a popular part of Appalachian and fisherman’s folklore, too. You can test this yourself by doing an exercise called fiddling or worm grunting.
Use a stick to hit the ground repetitively to make the soil vibrate and bring worms to the surface.
Why do worms leave the soil when it rains? Unfortunately, coming up for oxygen also has its risks.
Earthworms lying on top of the garden soil can get snatched up by birds and other kinds of earthworm predators. These worms can also get stranded and bake on an unforgiving surface when the sun comes out.
So far, according to Thea Whitman, a professor at the University of Wisconsin, scientists haven’t proved the mole-predator-escape theory in the lab. But it’s interesting to try to replicate the experiment at home.
3. They’re Moving Up
Why do worms come out in my garden after rain? The third explanation that scientists give for this vertical earthworm movement after a light or heavy rain is because they can.
Why do worms crawl out when it rains?
It’s generally hard and slow for earthworms to move around under the ground. Their sensitive bodies need to stay hydrated, so they would shrivel up and die if they stayed above ground.
After a rain, worms can navigate the soil more easily, locate mItes, try out a new area faster and easier above ground, or even hang out on top of the soil without drying out.
The wonders of the earthworm microcosm exist right under our feet and a rain allows us to observe their migratory behavior.
Final Thoughts
Why do worms come out of ground when it rains?
Now that you know why worms come out when it rains, you may wonder, Should you put worms back in the grass? According to experts, you can help an earthworm move off paved garden paths by putting the worm gently onto the grass nearby.
This will help them avoid getting squashed by people or baking in the sun.
Once earthworms are back on the grass, they can burrow beneath the surface to continue their beneficial garden tilling under our feet.
We hope this helps.
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Nadine is a passionate gardening writer sharing practical tips, innovative ideas, and valuable insights on plant and soil care, In her spare time, she tries to convince her plants to grow by singing them catchy tunes.