The short answer to whether snails eat other snails is yes, but this predatory behavior is not universal across the more than 65,000 species of gastropods. Snails are mollusks whose diets vary, ranging from specialized herbivores that graze on plants to highly adapted carnivores that actively hunt other shelled creatures. The difference lies in whether the snail is a true predator, an opportunistic scavenger, or a resource-starved herbivore. Consumption of other snails is a biological reality for certain species, even if it is not the norm for common garden varieties.
True Carnivores and Snail-Eating Predators
A distinct group of snails has evolved to be active predators, making other snails and slugs their primary food source. These specialized hunters possess adaptations that allow them to subdue and consume their shelled prey. One well-known example is the Rosy Wolf Snail (Euglandina rosea), a voracious terrestrial hunter native to the southeastern United States. This species is a molluscivore, meaning its diet consists almost exclusively of other mollusks.
The Rosy Wolf Snail tracks prey by following the victim’s slime trail, using specialized chemical receptors on its lower tentacles. Once it catches a smaller snail, it may ingest the entire creature, shell and all, to utilize the concentrated calcium. For larger prey, it extends its narrow, proboscis-like mouth into the shell’s aperture and uses its modified radula to rasp and suck out the soft tissues inside. This predatory efficiency caused significant ecological problems in areas like Hawaii, where it was introduced as a biological control agent but decimated native snail populations.
Another dedicated snail predator is the freshwater Assassin Snail (Clea helena). This species is popular in aquariums for its ability to control populations of smaller, nuisance snails. The Assassin Snail is an ambush hunter that uses a long, extendable siphon to detect food from a distance. It then uses its sharp, tooth-like radula and proboscis to pierce the shell or soft tissue of its victim, consuming the body. These carnivorous snails require a protein-rich diet.
The Typical Diet of Common Garden Snails
For most terrestrial snails, the diet is not predatory but herbivorous or detritivorous, focusing on plant matter. Common garden snails, such as the Brown Garden Snail (Cornu aspersum), primarily feed on decaying vegetation, fresh leaves, algae, and fungi. They play a role in breaking down organic debris and recycling nutrients back into the soil.
The mechanism they use for feeding is the radula, a ribbon-like organ located in the mouth covered in thousands of microscopic teeth. The snail extends this structure and scrapes it across the food source, acting like a file or rasp to break the material into digestible pieces. These common snails lack the specialized hunting apparatus and instincts of their carnivorous relatives and do not actively seek out other live snails as a standard food source.
A significant component of the herbivorous snail’s diet is the ingestion of calcium. They consume small amounts of soil, mineral deposits, or even pieces of concrete to obtain the calcium carbonate necessary for building and maintaining their shells. This constant need for calcium shapes much of their feeding behavior, and the focus on plant matter and minerals contrasts sharply with the protein-driven diet of predatory snails.
Cannibalism and Scavenging Behavior
Snails eating other snails can occur outside of active predation, often in the form of cannibalism or scavenging. Cannibalism, specifically the consumption of eggs, is common among newly hatched snails. Hatchlings often eat the shells of their own eggs immediately after emerging, providing them with a concentrated boost of calcium and nutrients. They may also consume unhatched eggs in the clutch, giving the early arrivals a nutritional advantage.
Scavenging, which is the consumption of dead or severely injured conspecifics (members of the same species), is an opportunistic behavior seen in many herbivorous species. This behavior is strongly linked to the need for calcium, especially in environments where the mineral is scarce, such as in acidic soil. By consuming the shell of a dead snail, the scavenger efficiently recycles calcium carbonate. This is a survival mechanism to ensure strong shell growth, which is a primary defense against predators and desiccation.
In extreme cases of calcium deficiency, some generalist snails, like certain species of Cepaea, have been observed gnawing at the shells of live, healthy snails. This shell-gnawing is not a predatory attack on the soft body but a desperate attempt to rasp calcium from the shell’s exterior. This behavior is a direct result of environmental stress and a profound lack of available minerals.