If you’ve seen dry silvery mucus trails around your house or yard, then it’s probably snail slime. But why do snails make all this slime and leave shiny tracks as they move along?

Snails have slime to help them with crawling, sticking to things, scaring off predators, communication, and protecting their eggs. Slime also protects snails from drying out, and from getting infections or cuts. Snails make different kinds of slime in glands in their body for different purposes.

Snail slime is what you see on your pavement, carpet, plants, walls, and anywhere else snails have crawled. Because of the way they move, snails sometimes leave a dotted trail whereas slugs always leave a slime trail in a solid line (though they both use slime for many of the same reasons). Slime is extremely important for a snail’s survival and understanding this can help you in your battle against snails.

Snails have slime for many reasons, including…

Slime keeps snail bodies moist (and alive)

A snail’s body must stay moist for the snail to stay alive. If a snail loses too much moisture, it shrivels up and dies. A snail controls its body moisture in two ways:

• A snail’s skin is designed to let water through it to maintain a balance between the outer skin and the cells inside. It does this with the humidity in the air, especially after it rains.
• The snail releases slime to coat its skin, which is a lot like applying body lotion to your skin after a bath to seal in moisture.

But snail slime is thicker than lotion and doesn’t get absorbed into a snail’s body. The following picture is an extreme closeup of a snail’s skin – see how wet it is?

Snail slime feels more like liquid gel. It’s mostly made up of water, and the rest is a mix of special proteins and carbohydrates. The protein in snail slime is designed to absorb water or humidity in the air, so the slime doesn’t evaporate or dry out. This is why snails prefer living in areas with a lot of humidity.

Slime lubricates the outside of a snail’s body, keeps the body moist, and helps the skin maintain a good water balance. So slime keeps a snail alive.

Slime prevents diseases and infections

Snail slime acts as a protective barrier between a snail’s body and germs.

Snails crawl over and eat a lot of dirty and unsanitary things, such as feces and trash, which carry a lot of germs. And because a snail’s skin is wet all the time and gets air for many hours every night when a snail is awake, there is always a risk of bacterial growth.

Lucky for them, the slime on a snail’s skin has antibacterial properties to protect a snail’s skin from infections and bacterial growth.

If a snail is awake and active during the day, which doesn’t happen often because snails are nocturnal creatures, its slime acts as sunblock and protects the snail from the sun’s UV rays.

Slime prevents cuts and scratches

A snail’s body is soft and squishy. As a snail crawls along, the entire underside of its body comes into direct contact with the ground and anything on the ground. The world is a dangerous place for softies like snails, and they often come across sharp objects like twigs and jagged surfaces like gravel pavements in their travels.

Without slime, a snail’s body would quickly get cut up and scratched by all these things.

Snail slime is thick and gel-like, so it protects a snail’s body from being scratched and cut by rough surfaces and sharp objects. In fact, snail slime does such a good job of protecting a snail’s body that a snail can crawl over a razor blade without getting hurt!

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Slime makes it easier for snails to crawl

A snail’s body is a muscular foot. When a snail wants to crawl forward, it sends pulses through its body muscle. These pulses move quickly, one after the other, from the snail’s tail to its head in waves of contractions, and these waves push the snail forward.

The following video shows a snail crawling across a window. If you look closely, you’ll see shadows moving across the snail’s body. But these aren’t shadows at all, they’re the muscle contractions or pulses moving the snail forward!

A snail’s body is strong enough to move on its own, but slime makes crawling and moving around easier.

Here’s the interesting thing about snail slime:

When a snail is still, its slime is sticky and thick like gel or glue. But when a snail crawls and puts pressure on its slime, the slime softens to become more like a thick oil or lubricant.

This oily slime makes it easier for snails to glide along and crawl, but it’s also what dries into the silvery snail trails you find in your house and yard.

Snails stick to things using their slime

We know that a snail moves forward by sending waves of contractions through its foot body. As these contractions move through the body, some of the body touches the surface that the snail is crawling on. This area of direct contact puts pressure on the snail slime and makes it oily, which makes it easier for the snail to crawl.

But some parts of the body lift off the surface briefly as the snail crawls. It’s at these lifted parts that snail slime becomes more like a sticky gel or glue. And this gummy slime is what keeps the snail stuck to the surface so it doesn’t fall or slide down to the ground.

Slime helps snails stick to things in three ways:

• Slime makes it possible for snails to crawl straight up vertical surfaces, such as tree trunks, steep rocks, windows, or the walls of your house.
• Slime is a snail’s secret to being able to crawl upside down on a ceiling or under the rims of plant pots, without falling off and breaking their shell.
• Slime keeps a snail stuck to bumpy and irregular surfaces. It also sticks snails to flimsy things that move around a lot in the wind or under the weight of the snail, such as leaves, so the snail doesn’t fall off.

Slime stops snails from being eaten by small predators

There are many things that eat snails, such as ants, firefly larvae, frogs, and ground beetles. They are a snail’s predators.

A snail uses its slime to protect itself from small predators in two ways:

• If the snail is being attacked by another small creature, such as an ant or larvae, there’s a good chance that the predator will get stuck in the snail’s slime. While the predator is struggling to free itself from the slime, the snail has time to crawl away or curl up in its shell for protection.
• When under threat, snails quickly start bubbling or foaming. Foam is a sign of distress in snails, but it can also block the opening to the snail’s shell so a small predator can’t crawl inside to attack it.

Snails also foam when they crawl over something that can poison them or when sprinkled with something that disrupts the balance of water in their skin, like salt. The bubbles act as a buffer between the snail and the substance, and show that the snail is unhappy.

Snails lock their shell with slimy mucus

Snails crawl into and hide in their shell when they think they are being attacked, when the weather gets too hot and dry for them to stay moist, or when it’s a cold winter and they want to hibernate until things warm up.

When snails know they will be in their shell for some time, they make a thick mucus or slime plug that covers the opening to their shell. This mucus dries into a seal, called an epiphragm, and it keeps the snail protected, warm and moist inside the shell.

Slime is a snail map for getting around

Snails leave slime trails as they crawl. They have very bad eyesight but they can smell extremely well with their tentacles. And one of the things snails smell and follow is snail trails.

Snails often follow a trail when they know where it will lead them, such as to food, their sleeping place, or to other snails (snails are social creatures and like to eat and hang around other snails of their kind). Snails also make and follow trails when they’re in a new habitat or extending their habitat, to get to know their new surroundings.

But snails don’t have to follow trails to find their way – it’s just one of the ways snails do.

Predatory snails, which is any snail that eats other snails and slugs, follow slime trails to track down a snail or slug to eat.

Snails “talk” to each other using slime

Snails use slime to communicate with other snails of their kind and even snails of other species. They do this by leaving chemicals in their slime trails, which other snails can smell with their tentacles and understand.

For example, if a snail is stressed it leaves a unique chemical scent in its trail. Other snails that pass by pick up this scent and know that there is probably danger on the path, so they choose another path to follow.

Slime makes mating painful, but more successful

When a snail is ready to mate, it uses its tentacles to sniff out a suitable partner to mate with. Once the sweet smell of another snail is found, the snail follows the other snail’s slime trail and crawls towards it.

Now it’s time to court each other. With darts.

The snails come close to get to know each other before mating. This is the perfect time for them to shoot each other with sharp slime-tipped darts, called love darts. This sounds romantic but cupid has nothing to do with it.

Snails are hermaphrodites, so they have male and female reproductive organs. When snails mate, they can fertilize each other’s eggs and it’s possible for both snails to lay fertilized eggs a few days later. But a snail’s reproductive system is designed to digest or destroy most of the sperm that enters it.

Snails mate with many partners. If one snail can successfully dart another snail it stands a better chance of fertilizing that snail’s eggs.

When the mucus on a love dart hits a snail, that snail’s reproductive system changes. It becomes more likely to store the love darter’s sperm and fertilize its eggs with it. The snail’s other mates who didn’t get a love dart in have very little chance of fertilizing the eggs – their sperm simply gets digested.

Once courting is done and the love darts have been shot, mating can begin. Snail slime will be used again once the eggs are laid…

Slime is an egg protector

Each mature snail lays about 425 eggs per year!

Once a snail lays a cluster of eggs, it covers the eggs in slime that is mixed with soil. The snail often poops on top of this egg cluster.

The snail slime protects the eggs from drying out in the soil and keeps the eggs stuck together and to the hole in which they are laid, so the eggs don’t get washed away or blown away by the wind.

If the eggs are kept moist and at the right temperature, baby snails soon hatch out of them and start making their own snail slime.