Slugs are snail-like mollusks with no shells or very small shells. They have voracious appetites and will eat garden plants and crops as well as other vegetation, especially seedlings and tender plants. (See References 3) However, slugs do provide some ecological benefits. They are a food source for many animals and they break down organic matter, which is important for recycling nutrients, such as nitrogen, through the food chain. (See References 1)
Slugs like moist environments with heavy, wet soil. They typically shelter in crevices beneath vegetation and under rocks, pots, mulch and in any area that retains moisture. They live in many places around the world and are eaten by numerous animals, including snakes, salamanders, toads, frogs, badgers, hedgehogs, moles, shrews, porcupines, foxes, raccoons, beetles and various birds, such as owls, robins, blackbirds, thrushes, starlings, seagulls, jays, ducks, geese, chickens and crows. (See Resources 1) For these creatures, slugs represent a good source of protein.
Among the animals that feed on snails are many that also feed on other organisms considered pests; some will also eat dead organic matter and may also prey on other animals. For example, foxes, owls and snakes consume mice and other small mammals; many birds help control insects like ants, mosquitoes and gnats, and some eat snakes, toads and other small amphibians and reptiles. (See Resources 1)
Slugs eat dead organic matter as well as living vegetation. Various species will feed on rotting plants, leaves, dead animals and even animal droppings. For example, the European black slug, Arion ater, eats dung and also lays its eggs in it. After hatching, the larvae live in the dung for three to four weeks. As decomposers, the slugs break down organic matter, thereby releasing nutrients which enrich the soil. (See References 1)
Not only do slugs clear an area of dead and dying matter, they also help spread seeds that are present in vegetation and dung. (See References 2) Not all slugs are voracious garden pests. For example, the banana slug is thought to favor mushrooms. It also eats lichen, algae, fungi and dead animals. On the other hand, the garden slug, Arion hortensis; the field slug, Derocereas reticulatum; and the keel slug, Tandonia budapestensis, can wreak havoc in gardens. (See Resources 1)