Do Snails Hibernate Or Die When It’s Cold? How They’ve Survived 500 Million Winters

by | Slugs & Snails, Snails

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If the temperature is dropping outside, there’s a good chance you aren’t seeing as many garden snails as you used to see. So where do garden snails go in winter?

Garden snails usually hibernate or overwinter in areas with very cold winters. They often cluster together in groups under leaves or rocks, then seal their shells, slow their heart rate, and sleep through icy weather. In warmer climates, snails don’t hibernate and remain active in winter.  

Snails have been around for 500 million years because they’ve developed many interesting ways to survive cold weather. Knowing where the snails in your yard go every year will help you find them and get rid of them, or stop them from coming around to breed in the first place.

Where do snails go in winter?

Two snails crawling on the stone on the bank of a mountain river.
These snails are looking for a dry, safe spot to sleep for the winter. They often hibernate in clusters, on rocks or under dirt and leaves.

In winter, snails go where they will be safe to sleep and stay dry. Garden snails hide under dirt and leaves, or they climb into pots, up on walls, under logs, in tree trunks, under rocks or in rock crevices.

Snails might spend the winter hibernating or sleeping alone, but instinct tells them they have a better chance of survival in a cluster so they tend to gather in groups for winter.

Studies show that snails have adapted to survive harsh winters. In fact, up to 73% of some snail species can live through extreme weather that reaches lows of 3 °F (-16 °C). And up to 91% of snails make it through mild winters.

In areas that have many cold winter days, garden snails prepare for hibernation:

They empty their stomachs to remove all liquids from their gut. If they don’t, these liquids can freeze and kill them.

The snails then curl up in their shell and seal the entrance to the shell with a thick mucus layer that dries out to become quite hard. This mucus layer is called an epiphragm (epi-FRAM).

Photo of large snail hibernating with a shell sealed with an epiphragm
This snail is hibernating. See how it has sealed itself in its shell with a white mucus layer? The mucus layer is called an epiphragm, and it protects the snail from the cold and predators.

A snail’s epiphragm:

  • Protects the snail from the cold, keeping moisture out so it doesn’t get into the shell and freeze the snail inside
  • Protects the snail from predators, like birds. When a bird swallows a snail, the epiphragm protects the snail from the bird’s digestive enzymes and the snail can survive. If it lives, it comes out the other side of the bird and carries on with life wherever it has been dropped
  • Attaches the snail to the surface of whatever the snail has chosen to sleep on for winter, such as a rock or a log

The snails lower their heart rate, take slow, shallow breaths, and slow down their metabolism, all to use less energy during this time.

Hibernation is done to survive the cold but it is also when snails get a deep rest that helps them live a long and healthy life.

Hibernating garden snails sleep through the cold and come out of their hiding places when they’re ready and the weather warms up. Some snails stay in this hibernation state for weeks or months, and others for several years.

In areas with milder winters, snails remain active and prefer to hide away and sleep only on colder days. These snails might seal their shells temporarily with a thin epiphragm for short periods of rest, but they don’t go into a deep sleep for a long period of time or change their body functions.

At what temperature do snails hibernate?

Garden snails usually go into hibernation once the temperature drops below 60 °F (15 °C), often after the first frost. In the northern hemisphere, most snails hibernate from October to April. Those that hibernate in the southern hemisphere typically do so from May to September.

The following video shows a snail waking up from its hibernation and the epiphragm (the white shell seal) that kept it safe during hibernation:

Do snails freeze or die in winter?

Snails have developed many ways to survive up to water’s freezing point, which is 32 °F (0 °C). One of the ways snails survive freezing point is because of glycerol, an antifreeze chemical, that they make in their blood.

Some snails make glycerol in winter, which consists of sugar and alcohol. The sugar in the glycerol binds with water in the snail’s body and allows the body to stay alive in a dehydrated condition. The glycerol also stops ice from forming in the snail’s body and destroying soft tissue.

Interestingly, some ants also use glycerol in their blood to prevent freezing to death in winter.

Hibernating garden snails can survive cold winters because of the glycerol antifreeze in their blood, but they usually die when the temperature drops below 23 °F (-5 °C). The glycerol is no longer effective past this temperature and the snail freezes to death.

Snails that don’t hibernate often die off in fall. They lay eggs that last through winter and hatch in spring.

But there is another thing that can kill a hibernating snail in winter…

A snail overeats in summer and fall to build up fat deposits. The snail uses these fat deposits for energy to keep itself alive and warm during winter hibernation. This is possible because the snail reduces its bodily functions to need 90% less energy than when it isn’t hibernating.

If the snail is woken up during hibernation, by an animal or person, its body temperature increases and it begins to breathe normally, hormones become active and the metabolism fires up again. The snail starts using a lot of energy, at least until it goes back into hibernation.

During this time, the snail might use up too much energy and not have enough reserved for the rest of winter, and it could die from starvation.

How to tell if a snail is hibernating or dead

A hibernating snail might look like it’s dead and a snail that’s dead could look like it’s hibernating. This can be especially confusing when the weather is cold.

So how can you be sure if the snail is sleeping temporarily or gone forever?

Here are the signs that tell you a snail is hibernating:

  • A hibernating snail does not smell bad. If you sniff the snail and it doesn’t smell like anything or doesn’t smell “off”, then it’s probably hibernating
  • You can feel the weight of the snail’s body inside the shell
  • The body is completely inside the shell, and it stays inside until the snail decides to wake up
  • There is a white covering sealing the entrance to the shell, which keeps the hibernating snail safe inside
  • The snail is fixed or sticking to a surface

Here are the signs that tell you a snail is dead:

  • A dead snail does not smell good as the meat is rotting inside the shell, or the body might fall out of the shell when you pick it up
  • The shell is light and empty, which means all the meat on the snail’s body has rotted away
  • The body is hanging limply out of the shell and does not move

If you see what looks like a snail but it doesn’t have an outer shell on its back, it’s not a snail but a slug. Slugs evolved from snails and found ways to survive without a protective shell.

How to get rid of snails in the winter garden

If you want to get rid of snails in the garden, winter is a great time to find them as they sleep a lot more or are hibernating in groups.

Below are the best tips and products from Amazon to help you get rid of snails in your garden:

  • To stop snails from coming into your garden before winter, wrap a copper snail mesh fence around the yard or your flower beds. Snails won’t cross copper as it reacts with the slime on their bodies and gives them what feels like an electric shock. Make sure the bottom of the mesh is below the ground’s surface so snails don’t crawl under it.
  • If you already have snails in your yard that are active before or during winter, scatter these pet and wildlife friendly snail bait pellets on your lawn, in your vegetable garden, or around your trees. Iron phosphate baits, like this one I recommended, are safer to use and better for the environment than other baits on the market. On the other hand, metaldehyde baits are poisonous to dogs and cats, and should be used with great care.
  • In early fall, stop watering your plants or water as little as possible to keep the yard dry. Snails don’t like dry conditions and will move on to wetter areas.
  • Attract snails’ natural predators to your yard and they will eat a lot of snails for you. Squirrels, birds, frogs, toads, and turtles all enjoy eating snails.
  • In late fall or winter, rake the ground to turn over leaves and loose dirt on the ground. Look under stones, in pots, under logs, in the soil under trees and bushes, on walls, on plant stems, and anywhere else where snails might be hiding or sleeping for the winter.
  • Collect all the snails and snail eggs that you find. If you raked properly, there’s a good chance you exposed many hiding snails. The ones you don’t collect will probably be eaten by predators or die from cold exposure.
  • Now it’s time to kill the snails. An easy method is to put the snails in a plastic bag, tie it closed, freeze the bag, and throw it out with the trash. If the snails are awake, throw them into a bucket of soapy water or crush them and leave them outside for predators to eat. Here’s a complete list of what to do with snails collected from your yard.

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