The inhabitants of tropical and subtropical regions are well aware of the sight of slithery invertebrates after every rainfall. What makes these worms emerge out of the soil? Is it water or rain or something else?
If they can survive in water why do they emerge on the surface after rainstorms?
In this post, we’ll know the reasons: Why do worms come out when it rains?
Scientifically, some species of worms are intolerant to water as they consume more oxygen at night. They will move up to get oxygen, while others stay in the soil even after rain. Another contributory reason is that wet soil promotes easy movement of crawlers. So they come out for migration purposes. Some researchers state that they emerge as a defense mechanism against predators and drowning.
The behavior of worms in rainfall s totally dependent on species. Interestingly, the subspecies of earthworms vary considerably n oxygen consumption and water tolerance. The species of worms relying more on oxygen can’t survive long in the water. So they will have to pop up to the surface to breathe.
5 Reasons For Why Do Worms Come Out When It Rains
There are many theories about worms coming out after the rain. Some are just theories without any known evidence. According to scientists, there are 5 known reasons for this phenomenon. Let’s discuss the reasons in detail:
#1- To Avoid Drowning
Scientists believe that worms come out of burrows in rain. They want to keep themselves safe from drowning. However, it is just a theory, not a truth.
Many researchers dont agree with this theory. They argue that earthworms breathe through the skin and require moisture. The drowning worm theory is just a myth and has nothing to do with reality. They are two valid reasons for not supporting this theory:
Worms have a tendency to live a life submerged in water. They spend half or almost full larval stage in water. They can drown as they dont have lungs. They breathe through the skin. The skin can get oxygen from water.
Worms have more tendency to hold their breath for a few days to a week underwater. So, the fear of drowning does not make sense here. They always need moisture in the soil to breathe through the skin.
#2- To Avoid Predator
Many scientists believe that they come out in fear of predators. After the rain, the predators of worms start digging burrows. To save the lives they arrive on the surface. But this logic is also weak. If predators can dig the burrows, they can kill them even if they are on the surface. It’s true the activity of caterpillars, insects, and many other animals increase on the earth. Some are searching for predators, while others are searching for food. Many worms can eat up other worms. If they stay inside the earth, they feel they are not safe. So, they come out after the rain.
Some birds and moles create a vibration on earth to facilitate the movement of worms. They will hit the ground by drumming feet and beak to check the presence of worms.
#3- To Get Oxygen
When it rains, the water fills the holes and burrows of worms. The flow of oxygen reduces to the habitat of worms. The rate of oxygen diffusion in water is a thousand times slower as compared to air. This makes it difficult for worms to breathe. So, they pop up on the surface to breathe.
This is somehow valid argument to some extent. However, it also requires further research. The question here is if worms can hold their breath to stay alive why do they come out after the rain. They should hold breathe and stay under the soil. The answer is that not all species of worms make the way out after rain except a few.
The species of worms that consume a low amount of oxygen at night will appear on the surface after rain. The reason is that this species can’t collateral water or rainfall. On the other hand, the species of worms that require a low amount of oxygen will not come out after the rain. It will tolerate water actively.
This research was conducted by Taiwanese researchers on species of Earthworm. It is published in the journal Invertebrate Biology. This research was conducted on the specimen of two species Amynthas gracilis and Pontoscolex corethrurus. Th first one fail to survive longer in water, while the second one survived longer without crawling out of the soil.
#4- Raindrops Produce Vibration like Moles
This theory is named predation-escape theory. It states that the sound of raindrops falling on the earth is much similar to the vibration caused by moles. It makes worms feel that moles are hunting or digging soil for predation. As a result, they come out on the surface. The common predator of worms is moles and birds. They beat the ground to let them emerge from the soil.
This theory is opposed by University of Wisconsin Professor Thea Whitman. He argues that rain patter is not much powerful as compared to the striking sound of moles. It would be unfair to compare the pattern of raindrops with predators of worms. This does not make sense.
#5- To Migrate Faster
According to soil experts, worms need moist soil to crawl easily. It becomes difficult for them to reach from one place to other when the soil is dry. Moving in dry soil can also make them dehydrated. When it rains, the soil gets enough water. This moist soil provides a better medium for worms to crawl and move up. The rainy days are migration days. They cant travel fast under the soil. SO, they come out after the rain to burrow to the next destination. However, you may encounter many failed migration strategies by worms in the end. It is common for you to find them across patios, laws, and dust bins. They are hundred times easy to move in the wet ground as compared to under the soil.
Garden lovers, keep reading about how to get rid of hammerhead worms as it’s challenging to kill them.
People Also Ask
Why Do Earthworms Come Out When it Rains?
Many species of earthworms are intolerant of water. They come out of the surface during rain to breathe. However, some species dont make their way out as they are tolerant to water. They also emerge in fear of predators and drowning. This is not an evaluated fact.
Why Do Worms Crawl on The Sidewalks When it Rains?
Worms find it easy to crawl on wet surfaces. They migrate on rainy days for this reason. The wet sidewalks provide a slithery medium to support migration. Worms have a tendency to breathe oxygen from water as they move on wet pathways.
The scientific reason for worms crawling out of the soil is obviously the need for oxygen. Not all worms come out in rain. The behavior of worms in rain is highly dependent on species and oxygen consumption requirements. The more the worm consumes oxygen at night, it is likely to emergy out in rainfall.
Other theories like beating drowning and avoiding predators are just myths.