The Pacific banana slug, a cousin of the snail, is a shell-less gastropod mollusk belonging to the genus Ariolomax. Banana slugs grow six to 10 inches in length --  making them the second-largest slugs in the world (after the Limax genus in Europe) -- and can live for as long as seven years. They are named for their roughly cylindrical shape and characteristic golden yellow color (often with dark spots). Banana slugs do come in other colors, including greenish-brown, nearly black, and even white. Though the less common colors may reflect the influences of diet, available light, moisture, age, health, and other factors, the basic coloration evolved to blend well with detritus and help slugs avoid detection by salamanders, garter snakes, raccoons, foxes, porcupines, crows, ducks, beetles, and other predators. Some predators avoid slugs so they won’t have to deal with the mucus coating (as by rolling the slug in the dirt).

Banana slugs are stenotopic, meaning that they can withstand only a limited range of variations in environmental conditions. The climate has to be reasonably mild because severe winter cold will kill them. They need moist environments because severe desiccation can kill them. Since detritus and related organic matter provides most of their food, rotting plant and animal material must be abundant. Mushrooms are a preferred food, but they’ll consume lichens, algae, fruit, seeds, and even animal droppings and carcasses