A slug is a gastropod, a land mollusk like the snail but lacking the snail's hard external shell. The slug's diet varies greatly depending upon the type of slug. While most slugs eat plants or fungi, some are actually predators.
What Slugs Eat
Slugs typically eat tender fungi and leafy plants. Favorites include cucumber and oxalis. Slugs also feed off flowering plants and even trees. Many times, slugs will live at the root of the plant, feeding on the roots and bulbs.
Unlike most slugs, the leopard slug, named for the dark spots on its light brown body, feeds off dead animal tissue, although it will also eat cat food and pet feces. This slug can be found throughout Australia, primarily in urban areas.
Banana slugs are one of the most common types of slugs. Their diet typically includes herbs, lichens, mushrooms and fruit, but, as with most slugs, they will also eat anything from animal waste to each other.
How Slugs Eat
The mouth is on the bottom of a slug and it ingests by crawling over the food. Slugs have a tongue-like organ, a radula, that they use to eat. This tongue is covered in thousands of protrusions called denticles. To find food, they taste and poke with retractable tentacles.
If a slug is disturbed or injured in any way, it secretes a sticky slime as a method of protecting itself from predators, predators that could potentially include other slugs. The slime also acts as a natural anesthetic. Native Americans have used the anesthetic properties of slugs for treating toothaches.