Featured Creature: Banana Slug

What slimy creature improves its forest ecosystem, uses clever tactics to impair predators, and might make you think twice about a favorite fruit?

The Banana Slug!

Slender Banana Slug; Photo from Santa Cruz Museum

You don’t usually think of slugs up there in the running for people’s favorite animals. Their blob-like shape and squishy texture can be notorious gross-outs for children and adults alike. But banana slugs, a genus of terrestrial North American slugs (Ariolimax) named for their bright yellow color and oblong shape, have become somewhat of a fan-favorite in communities around the world.

In California, the banana slug has become the mascot of UC Santa Cruz. They’ve also inspired the running tradition of International Slugfest, and many other community celebrations like the Russian River Banana Slug Festival. They even lend their name to the environmentally focused musicians in the Banana Slug String Band.

Maybe it’s because of their bright bold coloring, or the fact that they’re among the biggest slugs in the world, growing up to 9.8 inches (25 cm) in length. Maybe it’s the way they play a crucial role keeping the forest floor full of healthy porous soil. Or maybe it’s in their amazing survival tactics that include temporarily petrifying predators or hibernating for long periods of time. It could just be that fascinating slime!

It turns out, there’s plenty to celebrate about this little gastropod.

Photo by Such A Groke from iNaturalist

Slime Time

Banana slugs are covered in slime, which help them breathe and maintain the moisture needed for them to survive and move adeptly through their forest environment. This genus of slugs reside in the North American continent, with the majority of populations along the Pacific Coast. They are predominantly found in coastal coniferous rainforests like the majestic redwood forests of the Northwest, as these slugs value a nice wet habitat.

In fact, the slime that is so vital to the slug is produced by excreting dry granules of mucus, which absorb surrounding water molecules to produce lubrication. The mucus is composed of proteins called mucins that are organized in chains and have sugar molecules along the sides, whose patterns link the mucus together. Mucin patterns are what help the slug navigate different rough surfaces; the chains reorganize to coat sand or rocks, which is what allows the slugs to move through the forest.

Image by Flickr User John Loo

While their slime makes banana slugs capable navigators, they can’t claim to be particularly fast. Banana slugs move about 6.5 inches a minute, making them one of the slowest animals around. However, although they might be easily caught by hungry predators, the banana slug luckily has some deterring methods up its sleeve.

Banana slug slime has an anesthetic effect, filling a predator’s mouth and throat with numbing goo when they try to go in for a meal. When picking up a banana slug, you may find your fingers start to go numb, so take care before disturbing any forest friends!

Learn more about how this remarkable substance works:

When the banana slug faces particularly harsh conditions, it relies on a thick coating of slime to survive. Banana slugs are able to enter a hibernation state called “estivation”, in which their metabolic function is slowed. When these slugs are confronted with intense dryness or harsh winters, they bury themselves in debris, secrete a large helping of mucus, and go dormant, stirring again only when conditions are more hospitable.

Foundations of the forest

Banana slugs are an important feature of the forest floors they call home. As they move around, they collect leaves, fungi, fecal matter, and other organic materials to ingest. These creatures are decomposers essential to cycling nutrients through the ecosystem, taking in various sources and producing a rich humus enhancing the living soil. Sometimes banana slugs also eat berries, whose seeds are deposited straight into ideal nutritious conditions.

Banana slugs are in turn eaten by snakes and salamanders, and have also been consumed by humans, notably by the Yurok peoples of the Pacific and by some communities of German immigrants in the 19th and early 20th centuries. Whether by eating them, dressing up as them for a sporting event, or doing some amateur photography on a weekend hike, there are many ways to appreciate a banana slug. May we all take heart from this creature, and remember that resilience can mean much more than speed or strength.

Time to ooze away now!

By Maya Dutta