Slug Truth is Stranger than Fiction

Banana slug.
Banana slug.

Did you know that the coast redwood forest is home to the largest slug in North America and the second largest slug worldwide*?  Yep, our very own banana slug (Ariolimax columbianus) grows up to 8 inches in length and can live for 7 years.  Banana slugs depend upon the moist habitat provided by Pacific Northwest forests and crawl along their own slime trails in coniferous forests up through British Columbia.  Banana slugs secrete slime to aid in their locomotion, as defense from predators (beetles and raccoons), for reproductive purposes, and to keep from drying out. They eat a little bit of everything in the redwood forest including live plants, fallen leaves, and dead animals, but never munch on the redwoods themselves. The striking yellow color of the banana slug varies with the diet of the slug, light conditions, and general health, but it isn’t uncommon to see slugs with dark brown spots that help the slug hide on the forest floor.  Banana slugs breathe through a special lung called a pulmonata that is visible as a “hole” at the back of the head.

Perhaps the most fascinating aspect of the banana slug is their mating behavior.  These slugs are hermaphrodites and can actually fight quite aggressively before mating (the slug equivalent of biting).  It isn’t uncommon for one of the slugs to chew the penis of its mate and render it unable to fertilize other slug eggs.

Once again, truth is stranger than fiction.

Love these facts? Check out our Fun Forest Facts and leave a comment telling us what you’d like to know about in the redwood forest!

*The world’s largest slug is found in Europe, is gray, and grows up to 12 inches in length (Limax cinereoniger).

About the author

Emily Burns, the League’s former Director of Science, led the research program that includes the Redwoods and Climate Change Initiative. She holds a PhD in Integrative Biology on the impacts of fog on coast redwood forest flora from the University of California, Berkeley.

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2 Responses to “Slug Truth is Stranger than Fiction”

  1. Tim Upham

    Banana slugs are extremely critical to coniferous forests on the West Coast. They excrete nitrogen into the soil, and they transport seeds and spores. But are being threatened by the invasive leopard slugs. They are extremely aggressive, and will prey on native slugs, such as the banana slugs.

  2. Kelly Pomeroy

    Correction to the article on banana slugs: the breathing pore on the slug’s head is a pneumostome. Pulmonata is a taxonomic name for slugs and snails that have lungs instead of gills.


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