9 Reasons Why Snails Come Out When It Rains

by | Slugs & Snails, Snails

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If it’s been raining, you might notice a lot of snails crawling along the pavement or many active snails in your yard a few hours after the rain stops. I wanted to know why this happens, so I did some research and asked around to find the answer…

Snails come out when it rains because of water in the air, which they need to monitor so they don’t get too wet or too dry. They also crawl away in heavy rain to avoid drowning. But there are many reasons why snails come out in wet weather, and most are about timing and a basic need for survival.

Snails become more active in rainy weather, but you might not see them until the rain starts calming down or a few hours after the rain stops. Snails can’t talk so we can’t ask them why they do this, but many experts, observers, and snail owners have shared their theories on the topic.

Below I’ve put together all 9 reasons why snails come out when it rains and added my own personal insights so we can get a better idea of why this happens and how to get rid of snails after rainfall.

Snails want to find an area with less humidity in the air

A snail’s body must stay moist at all times. In fact, a snail’s body is made up of about 80% water (the human body is about 60% water). If a snail loses too much water and gets too dry, it shrivels up and dies.

The picture below is a close-up photograph of a snail’s skin – see how wet it is? A snail needs to keep its skin wet if it wants to survive.

Closeup photo of moist snail skin explaining how snails keep their skin moist with slime and water regulation
A close-up photo of a snail’s skin to show how wet the skin is.

When water evaporates from a lake, a sea, or wet soil, it rises into the air and turns into gas. This gas form of water is called water vapor. Humidity is the amount of water vapor in the air, for example “high humidity” means there is a lot of water vapor in the air.

Snails use humidity to control their own body moisture and the wetness of their skin. They spend a lot of time moving around to make sure that the humidity level is just right for them, and they will even climb trees, fences, and the walls of houses to look for more or to get away from too much humidity.

When it rains, especially if it rains for some time, humidity in the air increases to make it high humidity. This is often too much water vapor for snails to be happy. Snails come out when it rains because they need to find somewhere with a lower humidity level.

Snails crawl away from heavy rain so they don’t drown

Snails spend most of their day sleeping where predators can’t find them. To stay hidden, snails crawl under logs, bushes, boards, plant pots, rocks, or anywhere else they feel safe. Most of these places are on or near to the ground.

Land snails have a lung inside their shell that they use for breathing. They also have a small breathing hole underneath their shell that lets air in and out of their shell, which is the air they breathe with their lung (the breathing hole also happens to be where their poop comes out). Land snails cannot breathe underwater like water snails can, and they will drown if their shell fills with water and they can’t get air.

Photo of a snail lying upside down to show its breathing hole where snail poop comes out
Photo of the underside of a snail’s breathing hole, to show where air goes in and out for the snail to breathe with its lung.
Source: Image adapted, with thanks, to SeanMack

When there’s heavy rain, the area where snails are sleeping might become flooded with water or the ground could get very, very wet. All this water can fill the snails’ shells with water. The sleeping snails quickly wake up and travel, even in stormy conditions, to drier ground higher up, where they won’t drown.

Snails feel safer outside when predators hide from rain

There are many things that eat snails, such as birds, which is why snails stay hidden during the day if they can. Snails are nocturnal, which means they come out at night to feed, mate, and crawl around.

But when it rains, many snail predators retreat to their nests or homes to wait for the rain to stop. Because of this, snails feel safer moving around on rainy days and are more likely to come out of their hiding places.

Snails might wake up thinking it’s dusk

Snails don’t wear a watch so they can’t tell the time. But snails instinctively know that when the sky gets darker and the temperature cools down, the sun is usually setting and it’s time to wake up.

When it rains and there are heavy, gray clouds above, snails could think it’s dusk even if it’s the middle of the day. These snails are likely to come out and start moving around as they would on any other evening, at least until the clouds clear and the sun comes out again.

It’s easier for snails to crawl on pavements and roads

Two of the reasons why snails have slime is to help them crawl and to protect their body from getting hurt. Snails use pulses in their body to push their body forward, and the ground becomes smoother and safer thanks to all their slime.

But many man-made ground covers, such as bricks, concrete, tar, and stone paving, are hard, rough, and absorb snail slime. If a snail wants to cross this type of surface, it has to use a lot more slime than usual because the slime gets sucked into the surface and there’s a chance there won’t be enough slime to protect the snail’s body from getting scratched and cut.

Making slime takes a lot of energy and moisture from a snail’s body, so snails like to use their slime sparingly.

To minimize the amount of slime a snail needs to cross a hard, dry surface, it slows down and “lopes”. A loping snail is a snail that crawls forward on the front and back parts of its body, all while the middle of its body lifts off the ground. You will recognize a loping snail by the dotted trail it leaves behind, as can be seen in the picture below:

Photo of a loping snail showing how loping leaves a dotted slime trail behind to save slime
The dotted slime trail behind the snail shows that this snail is “loping” to save slime while crawling across the absorbent bricks. Snails lope by arching the middle of their body and crawling slowly using the front and back of their body.
Source: Image adapted, with thanks, to JohnRichfield

When it rains, absorbent surfaces become wet with rain water and no longer absorb a snail’s slime, so snails find it much easier to move across bricks, tar and concrete. This is why you often see snails crawling on pavements and roads after it rains, especially if they are out looking for dry ground or better humidity levels and the grass is too wet for them to cross.

Photo of snails crawling over rough tar road which is easier because the surface is wet
Snails find it easier to crawl over wet paving and wet roads after it rains because the wet surface doesn’t soak up all their slime.

Rain wakes up winter hibernating snails

Depending on the time of year, rain can wake up sleeping snails and bring them out of hibernation.

When snails live in areas where there are very cold winters, they often hibernate to miss icy or snowy weather. They do this by crawling deep into their shell and sealing off the entrance to the shell with a thick layer of mucus, which dries into a strong plug.

Photo of large snail hibernating with a shell sealed with an epiphragm
This snail is hibernating and has sealed off its shell with a dry mucus plug, called an epiphragm.

Spring is known for bringing rain:

As the days start getting sunnier and warmer, the ground starts warming up, which warms up the air above it as hot air rises.

With more sunshine and heat, more water evaporates from lakes, dams, and oceans. This water turns to gas, called water vapor, and makes the air humid.

The cold winter air mixes with the warm, humid spring air. This pushes the warmer air up into the sky, where the water vapor in the air condenses or gets compacted to make clouds.

The clouds then release this water as rain.

So how do spring showers wake up hibernating snails?

Rain pours water over a hibernating snail’s mucus plug. The mucus is dry during hibernation, but it gets wet and sticky again after coming into contact with enough water. This wakes the snail up, and gets it out of its shell and moving around.

Rain wakes up summer hibernating snails

Snails that live in places with very cold winters usually hibernate in winter. But snails that live in very hot places often hibernate in summer. This summer hibernation is called estivation.

Snails do not like moving around when it’s hot and dry because they can quickly dry out and die. This is one of the reasons why snails sleep during the day and come out to eat at night, when it’s cooler.

When the summer weather is too hot or too dry for a snail to survive, the snail curls up in its shell and seals the shell with a mucus plug that quickly dries out. The snail stays cool and moist inside the sealed shell, where it’s protected from the elements. It stays inside the shell to sleep and save energy.

But a lot of rain can dissolve the protective mucus plug and turn it back into the sticky, wet mucus it was before it dried out. This wakes up the snail and brings it out of its summer slumber.

Snails mate and lay eggs in wet weather

Snails usually breed towards the end of spring and in summer. If you live in an area that’s warm, has enough rain, and a fairly stable temperature all year round, snails might be happy to breed there in autumn or even throughout the year.

All a snail needs to mate with other snails or self-fertilize (snails have male and female reproductive organs) and lay eggs is the right conditions: high humidity and warm temperatures. This is a time when snails become more active, social, and more likely to mate with each other.

These conditions are also what makes it rain, which is why snails seem to come out to breed when it rains.

A few days after mating, snails look for damp soil to dig a hole and lay their eggs in. Each snail can lay more than 400 eggs a year!

Just like snails, snail eggs must stay warm and moist in the ground to survive, which is why snails love breeding in rainy seasons.

Closeup photo of a cluster of garden snail eggs to show what they look like
A closeup photo of snail eggs and how to identify them in your own yard.

Snails often need to eat after it rains

Rain can make snails very hungry – hungry enough to come out to eat.

There are two types of rain that make snails come out to eat:

  1. Rain that ends a dry season, when food was scarce and snails went hungry: This rain waters plants and starts a lot of new plant growth, which snails find delicious and will come out to eat.
  2. Rain that lasts a few days and makes it difficult for snails to get out and find food: As the rain dies down, snails come out to eat because they haven’t eaten in a while and they are very hungry.

How to get rid of snails after rain

There are many ways to get rid of snails and their eggs after it rains. Below are the best tips and recommended products from Amazon to help you get snails under control:

  • Handpick snails: One of the most effective way to get rid of snails when it rains is to go out and pick them up by hand (you can wear gloves while you do this) or set a trap to collect them in one place. Click here to find out how to set this trap and what to do with all those snails from your yard.
  • Use snail bait: In autumn, before the spring rain starts, sprinkle these organic snail and slug killer granules. This will draw out and kill hungry snails before they eat all your new plant growth in spring. The granules are biodegradable, safe to use around pets, children, and wildlife, and work in the rain. If the rains have started, you can put the granules in a plastic cup and lay the cup down on its side to keep the pellets as dry as possible (though this isn’t necessary).
  • Clean up your yard – remove mulch, especially bark and dead leaves, pick up wood and logs, throw away empty plant pots, and remove anything else where snails could hide or lay eggs when it rains. Keep your yard clear of all much and debris until you get the snails under control.
  • Set a beer trap: After the rain has stopped and you know snails are out looking for food, set a beer trap by putting a small plastic bowl in the ground. Put the bowl deep enough to leave 1 inch above the ground or cover the trap with a loose lid to stop insects from falling in. Fill the bowl halfway with fresh beer. Empty it out and put fresh beer in every night until you no longer find snails in the morning. If you don’t want to make your own beer trap, you can buy beer traps from Amazon.
  • Kill snail eggs in the soil: Snails lay their eggs in shallow holes in the ground about 3 to 6 days after mating. Wait a week after the rain has stopped, then turn over your soil to expose snail eggs under the surface. The eggs will soon dry out or get eaten, and they won’t hatch.
  • Attract natural predators: After it has rained, attract frogs, songbirds, and other snail predators to your yard. They will quickly get the snail population under control without the use of chemicals or baits. To attract frogs, put a pretty solar light in your yard near a pond or damp area. This attracts moths, which frogs like to eat. To attract songbirds, get a bird bath, a wild bird feeder, or put a nesting box in your yard.

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I'm Monique. I love gardening and spending time in my backyard growing things. Here's where I share what I know about backyard pests and what to do about them, so you can enjoy your yard too.

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MONIQUE

Monique loves gardening and spending time in her backyard, where she grows flowers, succulents, herbs, fruits, and vegetables.

Monique spends a lot of time researching how to protect her backyard from harmful pests and trying to attract beneficial insects and animals.

She shares everything that she learns and tests here at Backyard Pests.

 

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