Despite the fact that worms live underground, it is a well-known fact among people who collect worms for certain activities that when they feel some kind of vibration they come to the surface of the earth, exposing themselves completely.
Earthworms need to live in moist soil that contains organic matter. They usually live in the upper layers, but in winter they bury themselves more to escape the frost. When the weather is very hot, they do the same to avoid dehydration.
Worms are usually difficult to surface during the day, as they are sensitive to ultraviolet light and quickly lose moisture to the sun.
In fact, the famous “Reds” owe their accentuated pigmentation to defend themselves from light, something that their closest cousins, who build and live in deep subway galleries, do not have.
They are also more visible to predators when they venture above ground, so this can often make us reflect on what is the reason for such unusual behavior, which puts them at risk.
Earthworms avoid daylight but often come to the surface at night to feed and expel their detritus. During the day they only surface in exceptional circumstances, such as when their galleries are flooded by torrential rains.
Why do earthworms emerge in the presence of vibrations? What exactly triggers this reflection of the worm in nature is still a matter of debate: but there are two predominant theories.
The first theory is light rain, whose drops vibrate in a similar frequency range. The earthworms can then escape the penetrating water, which could wash out their pipes.
In the second theory, burrowing predators such as moles are questioned, whose digging activities can be heard accordingly.
Both theories of why worms are susceptible to vibration are related to a survival instinct of the worm, and it is very likely that both theories are correct, from a certain point of view..
Earthworms have a pronounced mole escape response, which is to quickly emerge from their holes and flee across the surface of the earth, this theory is supported by some research.
A US researcher named Kenneth Catania examined the vibration frequencies with which some earthworms (Diplocardia mississippiensis) can be most successfully attracted out of the ground.
They resemble the vibrations of crawling moles, but not those of rain. All over the world, birds and other animals specialize in removing tasty earthworms from the ground.
People who use worms as fishing bait use different techniques. In the southern United States, but also in Great Britain, there are “worm grunt” and “worm spell” tournaments.
Kenneth Catania, a life scientist at Vanderbilt University, has carried out several decisive tests that support this theory, the specialist in sensor systems for animals had gone to the wetlands of the Apalachicola National Forest in Florida, where the “worm grunts” pass on their tradition from generation to generation.
They drive a wooden stake into the ground and set it into vibration with a grazing steel rod. Catania first recorded these vibrations below the surface using geophones.
The right frequency attracted worms within a radius of more than ten meters from the earth, the closer to the stake, the more. Only after four and fifteen minutes did the animals crawl back down.
This refuted the thesis that worms leave their holes for fear of drowning. The frequency comparison then showed: The moles generate a broad vibration spectrum with a peak at around 200 Hertz, but it clearly overlaps with the narrower spectrum of the worm grunts, which is concentrated at around 80 Hertz.
Apparently, according to Catania, people like waders or other wormers play the role of “rare hunters” on the surface, which is less dangerous to worms than the underground mole. The researcher suspects that the escape mechanism he has now proven could be widespread among ground dwellers.
What about the other earthworm theory?
Well, I really respect Kenneth’s study and testing, but I really don’t like to take things for granted just because one person says so, I have my own questions.
For example, in the country where I live, there are no moles, So how can worms develop this instinct if there are no moles and they have never existed in a certain place?
The first thing I would like to know about the theory of worms and rainwater vibrations is if a worm can actually be drowned.
Can earthworms be drowned?
One might think that worms cannot be drowned, since they live underground most of the time, and their body is all wet, they do not have a nose and at first sight, no air inlet or outlet can be seen.
Earthworms do not have lungs or gills. They absorb oxygen directly through their moist skin.
Therefore, they do not drown and can survive several weeks in water if it is kept oxygenated.
However, in waterlogged soil, oxygen disperses more slowly and plant roots absorb what little is available, so the oxygen in the earthworm’s burrow can quickly run out.
Some species have metabolic rates low enough to tolerate this, but the common earthworm, Lumbricus terrestris, surfaces after a heavy rain to take in air, even draining the soil.
Do worms have sensors?
Earthworms are called annelids or segmented worms since their body is split into several segments or sections. They cannot see, hear, or smell. Yet, their shortcomings do not seem to bother them at all.
In order to be able to find their way in subway regions, earthworms depend on their sensory devices, called prostomies near their mouths, and on sensory receptors they have in their skin to detect light and feel vibrations.
How do you catch worms with vibrations?
Worms tend to react to vibrations created by rubbing the top of a wooden stake with a flat piece of metal. Most of the charming worm methods involve vibrating the ground, which causes the worms to come to the surface.
Both of these theories about why vibrations attract worms to the earth have proven evidence, that worms are highly sensitive living beings, and that practically their entire body is a sensor.
And since every living thing has a high response to survival, coming to the surface by vibrations whether caused by rainwater or some other predatory animal is entirely natural and understandable.
It is also known that worms come to the surface to mate under the cover of darkness, but it is believed that there is something else that pushes them to the surface in wet weather.
Scientists believe that humid environments are the ideal terrain for worm migration, especially during darkness; this allows them to move to new areas, (they have been proven to cover up to 50 meters in search of food) overcoming the risk of hungry birds or getting stranded on the pavement.