Banana slugs are the delightful decomposers of the Northwest

Banana slugs play an important role in the ecosystems of the Northwest.
Banana slugs play an important role in the ecosystems of the Northwest. Courtesy

Slugs. They’re slimy. They’re sticky. And they make some people squirm.

The largest type of slug in the United States, named for its yellow body, is the banana slug. Some banana slugs also have brown spots, making them look even more like ripe bananas.

These humble yellow blobs are sometimes considered pests — but banana slugs play an important role in forest ecosystems by cleaning up the forest floor.

Decomposers help new life grow

For animals to grow, nutrients must be available in the soil and plants where they live. But where do those nutrients come from?

Although new energy can be added to ecosystems (in the form of sunlight, for example), new nutrients are rarely added. Instead, nutrients must be recycled and reused. This exchange happens in small ways throughout an animal’s lifetime, but is most obvious at the end.

When an animal dies, its body decomposes. Decomposition, the process of breaking down into smaller pieces, is a natural part of life and means that molecules can be returned to the ecosystem for other living beings to use.

But this process doesn’t happen by itself. When organic matter is ready to be recycled, special animals, bacteria and fungi arrive on the scene to help with this very important process. The crew is known as “decomposers,” and their job is to break down organic matter so that it is returned to the soil.

Groovy gastropods

In the Northwest, some of the best-known decomposers are snails and slugs. These animals are both gastropods — a name that comes from the Greek words gastros, meaning “stomach,” and podos, meaning “foot.” Indeed, snails and slugs squirm around on a single, slimy, stomach-like foot.

A slug looks like a snail who has lost its shell — and evolutionarily speaking, that’s exactly what it is.

Although a snail’s portable home may seem like an obvious advantage, there are also benefits to being shell-free.

Because they aren’t carrying anything on their backs, slugs are able to fit into smaller spaces. They are also able to live in a wider range of habitats because they don’t need the calcium required to build and maintain a shell.

However, slugs still face the challenge of living on land while keeping their bodies moist.

How does a slimy, wet slug survive in the air without drying out? With its signature slime. The slime produced by slugs is called mucus. It acts as a barrier between a slug’s body and the terrain it is crossing so that it can avoid losing moisture from its body.

Mucus also helps slugs attract mates and enables them to breathe through their skin. Slime may seem like an alien feature to us, but serves many functions for a slug.

Banana slugs at home

Banana slugs are fantastic decomposers because they eat a lot of materials discarded by other living beings in the leaf litter, such as dead plant materials and animal droppings.

A damp forest floor in the Pacific Northwest is a great place for a banana slug. You can find them yourself if you spend enough time camping, exploring or hiking. To spot slugs and other interesting creatures, keep your eyes to the ground — and try gently turning over small logs or pieces of bark to reveal moist and cozy hideouts underneath.

You may even find a slug by following the shiny trail of mucus it leaves behind.

If you are lucky enough to find a banana slug in the wild, it’s best to admire it from a distance without using your fingers. And if you have moved a log, be sure to put it back carefully.

Celebrate at Slug Fest

Although they may not be the cuddliest members of the forest, banana slugs deserve to be celebrated for their work as decomposers. Without slugs and other decomposers, the forest floor would become overrun with plant and animal waste, rather than a beautiful place for regrowth.

Banana slugs are celebrated at an annual event at Northwest Trek Wildlife Park in Eatonville. Slug Fest, to be held June 25-26, includes slug-themed games and activities. Visitors can learn all about fascinating slug anatomy, and enjoy hands-on crafts and more. Plus, you can wiggle your way down a soapy, slimy track in the famous “slug races.”

To learn more, visit nwtrek.org.