We have all experienced stepping out into the rain to find the sidewalk full of worms. Then the next day, there are dried-up worms all over the pavement. This brings us to the question: why do earthworms suddenly appear in the rain?
Earthworms come out of the soil during the rain because they mistake the raindrops for predators and try to flee. Once they reach the surface, it is moist enough to support them, and they stay above the ground to travel and mate.
This article will discuss the reasons that worms come out of the soil during the rain, challenge popular myths, and talk about the types of worms you may see on a stormy day.
Reasons Why Earthworms Come Out During the Rain
Worms don’t just come out during the rain to die. There are a few different things that drive this behavior. If you see a lot of worms have come out after a rain, you can be sure at least one of them is at play.
Fear of Predators
Worms don’t have ears or eyes. Although they can often perceive light, it is not a helpful ability underground. Instead, they rely solely on vibrations to take in their surroundings. When raindrops hit the earth, they create vibrations that worms mistake for predators.
Worms have many predators, including moles, foxes, and humans. All of these predators dig holes to try to reach the worms. In an attempt to avoid predators, worms will travel up and over at an angle, eventually taking them to the surface. Worms cannot differentiate between the vibrations of a predator and rain, so they flee in the same way.
Humans and birds have learned to use this same technique in order to lure worms to the surface. Birds peck at the ground to simulate vibrations, while fishers collect worms by placing a stick in the ground and tapping it with a piece of metal. Both approaches create the same vibrations as predators and trick the worms into coming out of the earth.
Worms need moisture to survive, so spending time above ground is not usually an option. However, once they get to the surface and find that it is moist enough to survive, they will stay for a bit to travel and find a mate.
Moving through dirt can be a pretty slow process. Depending on their size, earthworms can travel anywhere between 27 and 240 ft (8.2 to 73.15 m) every hour underground.
At this rate, the largest, fastest worms can make it just over a mile (1.61 km) each day while underground. Rainy days spent above ground allow them to travel further.
When the sun is out, worms are forced to remain in the soil. Instead of breathing as mammals do, worms absorb moisture with their skin. This need for water means that worms cannot survive in the sun and on the dry ground.
When it rains, the earth’s surface becomes wet enough to support the worms. They take this opportunity to travel or migrate longer distances than they could underground.
Not only does the lack of soil allow the worms to travel faster, but the wet ground also helps them to wiggle around faster.
Finding a Mate
Most of the time, worms mate underground. However, when they’re above ground, they take advantage of the opportunity to breed more easily.
Earthworms only have to pass next to one another and swap slime to reproduce, a process made simpler without dirt in the way. It is also much easier for worms to find mates above ground.
Reproducing is a significant part of a worm’s life. Earthworms reproduce every ten days, allowing worm populations to grow rapidly, almost doubling every two to three months.
Nightcrawlers, a common type of earthworm around the world, are one of the only species of worm that breed exclusively above ground. Other worms can mate both above and below ground.
Some worms will choose not to mate above ground because it makes them feel vulnerable. The vibrations caused by the raindrops make it difficult for them to detect predators.
Birds can sometimes peck at the ground to lure a worm or two out of the soil, but rainy weather is when they have the best access to worms. They try to take advantage of all the worms out in the open.
The Myth of Worm Drowning
The question of why worms come out of the soil when it rains has been asked for a long time. Initially, people assumed that worms came up to the surface in order to avoid drowning underground. Although this theory is sometimes still presented today, it is incorrect.
Worms need moisture to survive, which is why they live in the ground in the first place. The moisture in the ground keeps them alive when it is dry outside.
Instead of breathing air the way we do, worms receive oxygen through water, which they absorb through their skin. Like us, worms take in oxygen and put out carbon dioxide. But unlike us, worms don’t have lungs, so the oxygen they absorb is sent directly into their bloodstream.
However, there is a limit to this. Humans cannot drown in air, but if you put a person in a sealed space for an extended period, they would eventually use up all of the oxygen in the air and be left with only carbon dioxide. This need for new oxygen also applies to worms.
Once worms have exhausted all of the oxygen in the surrounding water, they will begin to die. They would have to be completely submerged in water for at least a week to be in danger.
The Myth of Worm Suicide
You have probably walked outside after a shower and seen plenty of dried, dead worms on the pavement. Although it seems that these worms must have intended to die, that is not the case.
Worms cannot sense when the environment begins drying up until it is already too dry. If they find themselves on the ground, they have time to burrow back into the soil, but worms on sidewalks, roads, and other hard surfaces often can’t make their way back in time.
Remember that worms cannot see, so they have to be lucky enough to come across the grass in time. If you see a worm struggling to move after it has rained, you can always help it by bringing it over to nearby soil.
We may not completely understand the behavior of worms, but we definitely don’t have any reason to believe they would want to commit suicide after it rains.
Not All Worms Come Out of Soil During the Rain
After heavy rain, it may seem as though every worm in the area has come to the surface, but this is not the case at all. Worms don’t have to come out during the rain. In fact, most of them don’t do it.
There are thousands of different species of worms, and some are more likely to surface in a storm than others. Nightcrawlers are a prevalent species of earthworm that mates above ground, so they take advantage of the rain to mate.
Besides, if most worms came out of the soil during rain, there wouldn’t be enough worms left to maintain their population.
It is interesting to note that, regardless of the species, only adult worms seem to come to the surface during rain. Although scientists do not know why this is the case, it reinforces the idea that worms come out to mate and avoid predators. Young worms cannot mate and may not have yet learned the signs of danger.
Worms need a moist environment to survive, and they use rain as an opportunity to spend some time above ground. Although they initially surface for fear of predators, they take advantage of their time on the surface to travel and mate.
Old claims that worms surface to commit suicide or avoid drowning have since been disproven by science. It is extremely difficult for a worm to drown, and worms stranded on paved surfaces after the rain are simply unlucky.