by Erin Marissa Russell
Ready to find out about snails versus slugs? These little creatures that can wreak such havoc in the garden share a lot of similarities, but they have plenty of differences as well. Keep on reading to find out more.
Snails and slugs are both part of the mollusk family, the phylum Mollusca, which also includes squids, clams, and oysters. Though they share the same family, they are organized under different superorders. Snails are classified in the superorders Neritimorpha, Caenogastropoda, and Heterobranchia. Slugs fall under the suborders of Orthurethra and Sigmurethra.
Slugs and snails are also called gastropods. This name comes from the Greek words for stomach (gastros) and feet (podos).
Snails Versus Slugs: Appearance
Both snails and slugs are relatively small. They look similar, with the exception of the snail’s spiraled shell. Snails’ bodies are coiled like the shell they rest inside. Snails and slugs both have a pair of tentacles that emerge from the head, and each tentacle has an eye at the end.
Snails can grow to be an average of 10 inches long, while slugs can reach around 15 inches long. However, these averages leave out the size variation to be found in outliers. Large black slugs grow to around 2.5 centimeters long. The world’s largest snail, the giant whelk, has a shell that averages 28 inches long. The largest slug in North America is the banana slug, which can reach up to eight inches long.
Snails Versus Slugs: Diet
As you probably already know, both snails and slugs eat plants. They leave behind ragged holes where they have been feeding. Slugs will also eat carrion and occasionally worms and snails.
Snails Versus Slugs: Predators
Snails and slugs are eaten by lots of small animals. These include beetles, birds, snakes, toads, and turtles. People eat land snails as well, most notably as a part of French cuisine as escargot.
Snails Versus Slugs: Behavior
Though they share so many similarities, slugs and snails have very different patterns of behavior.
Snails sleep for a 13- to 15-hour cycle. When they wake up, they spend the next 30 hours searching for food. Where conditions are damp, snails will keep to this schedule fairly regularly. However, if it is dry, they can sleep for up to three years.
Slugs are nocturnal creatures that emerge from their hiding places at night to feed. Though some slugs eat snails, worms, or carrion, many slugs live solely on plant material.
Snails hibernate during the winter and come back out again in spring. Slugs don’t hibernate, but they do overwinter, tunneling underground where it’s warmer to protect their soft bodies. Sometimes, slugs die underground before winter ends, but their eggs laid underground will hatch in the springtime.
The way snails and slugs move is another difference between them. They both move using a foot and the slimy residue you’ll sometimes see in your garden where snails or slugs have been. The snail uses muscle contraction and relaxation to move over the ground. Snails move more slowly than slugs because the foot must retract completely so the snail can move. The way snails move burns up a lot of calories, which is one reason why they must eat in 30-hour shifts. Slugs move faster than snails, using their feet to set their direction. Snails tend to move at an average of a millimeter per second, while slugs travel at different speeds depending on the species.
Slugs can live to be between one and six years old. Snails in the wild live for two or three years, but a snail in captivity (such as in an aquarium setup) can live to between 10 and 15 years old.
Snails Versus Slugs: Environment
Snails and slugs can be found all over the world, living on land, the desert, in trees, or in fresh water or salt water. They like to live where it is dark, damp, and foliage is plentiful. Some even spend wintertime underground. Snails can also live in trees or behind leaves.
As a rule, snails are more adaptable to different environments than slugs are. They evolve to have specialized traits that suit their environments.
Slugs, for example, don’t live in the desert or inside of trees.
Snails Versus Slugs: Shells
Snails have a spiral shell on top of their bodies, whereas slugs do not have an external shell. The external shell allows snails to retract and hide inside if they encounter a predator or a sharp object. Baby snails do not have shells. The shells are formed from calcium the snail takes in as it feeds. Once a snail’s shell is finished, the snail is an adult and can breed.
Slugs do have a shell, although it isn’t visible from the outside. The slug’s shell is small and internal. This internal vestigial shell allows the slug to stockpile nutritious calcium inside its body.
If you’re encountering slugs and snails (or the damage they leave behind) in your garden, you may be interested in our articles How to Protect Seedlings from Slugs and Snails, Slug and Snail Pest Control, or How to Control Snails and Slugs in the Garden.