Banana slug
A long yellow slug, sometimes as big as a real banana, that glides across the damp floor of the redwood forest and cleans up what falls there.
We saw it Our family spotted this one at Olympic National Park in July 2026.
Banana slug at a glance
Ariolimax columbianus buh-NAN-uh slug; Ariolimax columbianus is air-ee-OH-lih-max koh-lum-bee-AY-nus
- Type
- Invertebrate · mollusk
- Diet
- Decomposer
- Size
- Often 6 to 8 inches long (15 to 20 cm), about the length of a real banana, which makes the Pacific banana slug one of the largest slugs on Earth.
- Lifespan
- Around 1 to 7 years in the wild.
- Conservation
- Not evaluated (not on the IUCN Red List; common in Pacific coast forests).
Eats fallen leaves, mushrooms, dead plants, animal droppings, moss
A banana slug is a recycler of the forest floor. It scrapes up rotting leaves, dead plant bits, mushrooms, and droppings with a tongue covered in thousands of tiny teeth, called a radula, and turns them into rich soil the big trees can use. When it eats seeds and spores, it also helps spread them around the forest.
Should you worry?
Harmless. A banana slug cannot bite or sting and is not poisonous to touch. It is coated in slippery slime, and if you hold one your fingers may go a little numb where the slime touches, so look closely, touch softly with one finger if a ranger says it is okay, and never pick it up and carry it off. Wash your hands after. Do not lick a slug.
On a cool, misty morning in the redwood forest, something bright yellow is crossing the trail in no particular hurry. It is about the length of a real banana, sometimes spotted like a banana going ripe, and it leaves a shining trail of slime behind it. This is a banana slug, one of the largest slugs on Earth and a signature animal of the damp forest floor beneath the coast redwoods.
A banana slug is the forest’s cleanup crew. It slides over fallen leaves, dead plants, mushrooms, and animal droppings and scrapes them up with a tongue covered in thousands of tiny teeth, called a radula, turning the litter into rich soil the giant trees can use. Its slime does more than help it glide. It keeps the slug from drying out, lets it hang upside down under a leaf, and tastes so bad that it can make a hungry animal’s mouth go numb, so most predators leave the slug alone.
Banana slugs come out when the air is cool and wet, especially after rain, low on the shady floor at Redwood, on logs and along the edges of the trail. They are harmless. A banana slug cannot bite or sting, though the slime can leave your fingers tingling, so the best plan is to kneel down, look closely, touch softly with one finger at most, and wash your hands after. Then watch it inch on across the leaves, in no hurry at all.
Did you know?
- A banana slug breathes through a hole in its side. That round opening near the front, called a pneumostome, opens and closes to let air into a simple lung inside the slug's body.
- Its slime is a superpower. The slime helps the slug glide, keeps it from drying out, and can make a hungry animal's mouth go numb, so many predators leave it alone. The slime is so sticky it can hold the slug upside down under a leaf.
- Banana slugs help grow the tallest forest on Earth. By eating fallen leaves and droppings and turning them into soil, and by spreading seeds and mushroom spores in their droppings, they help feed the coast redwoods towering above them.
Common questions
Why is it called a banana slug?
Because it is often yellow and about the size and shape of a banana. Some are spotted, like a banana going ripe, and a few are green, brown, or almost white.
Is it safe to touch?
It will not hurt you, but its slime can make your skin tingle or go numb, so touch gently with one finger at most, never pick it up to carry away, and wash your hands after. Never lick one.
What does a banana slug do for the forest?
It is a cleanup crew. It eats fallen leaves, dead plants, and droppings and turns them into soil, and it spreads seeds and mushroom spores that help the forest grow.
Why is it so slimy?
The slime lets it glide without drying out, helps it stick to leaves even upside down, and tastes bad to animals that might eat it.
When can I see one?
On damp, cool, misty days, especially after rain, low on the shady redwood forest floor, on logs, and along trail edges.