Animal
Pacific banana slug
The Pacific banana slug is a big yellow slug that lives in damp forests. It glides along on its own slime and helps clean up the forest floor.
The Pacific banana slug is one of the biggest slugs in the world, often as long as a banana and sometimes yellow like one. It lives in the damp rainforests along the Pacific coast of North America, where it eats fallen leaves, mushrooms and other plant matter, helping to recycle the forest.
Ariolimax columbianus is a large terrestrial slug, 185 to 260 millimeters long, of the temperate rainforests from central California to southeast Alaska. A detritivore and hermaphrodite, it depends on moisture and its mucus to breathe, move and avoid drying out, and in places it now faces competition from the introduced European slug Arion rufus.
Photo: Thomas Schoch, CC BY-SA 2.5, via Wikimedia Commons
Meet the Pacific banana slug
The banana slug is a big, soft slug with no shell.
Many are yellow like a banana. Some have dark spots. It slides along on slime, very slowly.
The Pacific banana slug is a very large slug, usually 18 to 26 centimeters long, about the length of a big banana. Like snails, slugs are mollusks, but a slug has no shell on its back.
Banana slugs come in many colors: bright yellow, dark yellow, and mixtures of brown, black, white and green. Many have dark brown or black spots, like an overripe banana. They have smooth heads, and many have a ridge running along the back.
Ariolimax columbianus (order Stylommatophora, family Ariolimacidae in the GBIF classification; some keys place it in Arionidae) is a very large land slug, 185 to 260 millimeters long (The Evergreen State College key). Color is variable, from bright to dark yellow with brown, black, white or green, often with dark spots; the spotted form has been called forma maculatus, but it is not a true subspecies.
Other identifying features are a wide foot margin with dark vertical lines and a conspicuous breathing hole. The species is an icon of the Pacific Northwest and the mascot of the University of California, Santa Cruz (Olympic National Park).
Quick facts
- Group
- Invertebrate
- Length
- 18.5 to 26 cm
Where it lives
Banana slugs live in rainy forests near the Pacific Ocean.
They need it to be damp. They come out most when it has just rained.
Pacific banana slugs live in the temperate rainforests along the western coast of North America, from central California to southeast Alaska. Some of these forests get more than 12 feet of rain a year.
They live on the forest floor, under ferns and on logs, and they can even climb trees, up to about 20 meters off the ground. They are found from near sea level up into the mountains, to about 1,370 meters. They are most active on damp mornings, in light rain or after a storm.
Olympic National Park places the species in the temperate rainforest of the western coast from central California to southeast Alaska; GBIF records come overwhelmingly from the United States and Canada. The Evergreen State College key describes it as usually restricted to forests and woodlands, on the ground and up to about 20 meters into trees, from near sea level to about 1,370 meters.
The NPS reports that on San Juan Island, Washington, the native banana slug does not inhabit grasslands, while the introduced Arion rufus occurs in both woods and grassland. Moisture governs activity: the slugs are most active when humidity is high.
Continent
Its habitat
Where can you find this animal?
- Lives here naturally · Countries and seas named by a scientific source
- Sightings recorded · Records of wild sightings (GBIF)
Lives here naturally · Countries and seas named by a scientific source
Temperate rainforests and woodlands along the Pacific coast of North America, from central California to southeast Alaska, including British Columbia. The map shades whole countries; the slug lives only in the moist coastal forests.
Places: United States and Canada.
Source: https://www.nps.gov/olym/learn/nature/slugs.htm · checked October 2026
Sightings recorded · Records of wild sightings (GBIF)
Counts of GBIF records of wild observations (human and machine) and preserved specimens. Records include introduced populations, vagrants, escaped or released animals and misidentifications, so a country with records is not necessarily part of the native range.
Wild sightings have been recorded in United States, Canada, Mexico and Netherlands.
Source: gbif · checked October 2026
Range maps show where scientists say an animal lives, often country by country. An animal may live in only part of a country shown, and sightings records can include animals that wandered far from home.
What it eats
Banana slugs eat leaves, mushrooms and other plants.
They also eat old, dead leaves on the ground. That helps clean up the forest!
Banana slugs eat leaves, mushrooms, lichens and other plants, and they also munch on dead plant material on the forest floor. Animals that eat dead matter like this are called detritivores, or decomposers.
By eating fallen leaves and turning them into droppings, banana slugs help return nutrients to the soil. They also eat fruit such as raspberries and blackberries, and may help spread their seeds. They scrape up their food with a ribbon covered in thousands of tiny teeth, called a radula.
The Evergreen State College key lists vascular plants, fungi and lichens in the diet, and the NPS describes slugs as nocturnal detritivores; Olympic National Park notes them eating leaves and mushrooms and calls them decomposers that help return energy to the earth. Little is known about their exact feeding preferences, which is one focus of research on San Juan Island.
Food is rasped by the radula, a ribbon of microscopic teeth; Olympic National Park gives a figure of up to 27,000 teeth. Redwood National and State Parks describes banana slugs as detritivores of decomposing plant and animal matter and feces, important in nutrient cycling, and also as fruit-eaters that may help disperse the seeds of raspberries and blackberries.
Did you know?
The banana slug is a university mascot.
The banana slug is the official mascot of the University of California, Santa Cruz.
An icon of the Pacific Northwest, the banana slug is the official mascot of UC Santa Cruz (Olympic National Park).
A body made of muscle and slime
A banana slug has four feelers on its head.
The top two feelers have eyes at the tips. It breathes through a hole on its side.
A banana slug has four feelers. Tiny dark eyes at the tips of the two long upper ones detect light and movement, and the shorter lower ones feel and smell. Just behind the head is a smooth patch called the mantle, with a breathing hole on its right side.
The slug moves on one big muscular foot. Its slime works a bit like ice under an ice skate: it helps the slug glide forward. Slime also keeps the slug from drying out and can even make a predator's mouth go numb.
Olympic National Park describes the slime's roles: it keeps the slug from drying out, helps it breathe through moist skin, lubricates movement on a single foot, and acts as a defense against predators such as birds, numbing a predator's mouth. The breathing pore (pneumostome) is on the right side of the mantle (Redwood National and State Parks) and may be seen open after rain.
The Evergreen State College key notes a wide foot margin with dark vertical lines and a conspicuous breathing hole. National Geographic describes the banana slug's four tentacles: the upper pair carries tiny eyes at the tips that detect light and movement, the lower pair feels and smells, and a lost tentacle can grow back.
Growing up
Every banana slug can lay eggs.
The eggs are white and small, like little pearls. The babies hatch and look like small, pale slugs.
Slugs are hermaphrodites, which means each slug has both male and female parts. When two slugs mate, one or both of them can go on to lay eggs.
A slug lays its eggs in a safe, hidden place, such as under a log. Pacific banana slug eggs are white and about a centimeter long. Olympic National Park says the babies hatch in one to two months, look like small, often paler slugs, and grow quickly.
Olympic National Park describes slugs as hermaphrodites in which one or both partners may be fertilized at mating, rarely self-fertilizing, followed by a clutch of 3 to 50 eggs laid in a secluded place. The young hatch in one to two months, resemble adults though often paler, and grow quickly toward maturity.
For A. columbianus specifically, The Evergreen State College key describes opaque white eggs about 10 by 8 millimeters. Redwood National and State Parks notes that fertilized eggs are laid under logs or in leaves, and National Geographic that the parent leaves the clutch once it is laid.
Slow and steady
Banana slugs move very slowly.
They like cool, wet days. On a dry day, they hide to stay damp.
Banana slugs are slow, but they are always busy recycling. They are most active at night and on damp mornings, in light rain or after a storm, when the air is wet.
You can often tell where a banana slug has been by the shiny trail of slime it leaves behind. If you see one on a trail, watch your step. Always put back rocks and logs you look under, because they are homes for slugs and other animals.
Slugs are nocturnal (NPS), and banana slugs are most active in high humidity, after rain or on damp mornings (Olympic National Park). Slime trails mark their movements.
Research by Erika Iyengar and her students in San Juan Island National Historical Park, reported by the NPS in 2018 after four summers of surveys, found that the relative frequency of the native banana slug and the introduced Arion rufus is shifting dramatically in some locations, with the invasive species becoming much more common, perhaps partly because of drought; whether Arion rufus outcompetes the native slug is still an open question.
Did you know?
Banana slugs can climb trees!
Banana slugs are usually on the ground, but they can climb as high as about 20 meters up into trees.
Found on the ground and up to approximately 20 meters above ground in trees (The Evergreen State College key).
Banana slugs and people
Banana slugs are important forest helpers.
We can help them by staying on trails and keeping forests healthy.
The Pacific banana slug has not been assessed by the IUCN Red List. It is still common in many Pacific Northwest forests, but scientists are watching a slug from Europe that people brought over in the last hundred years. In some places on San Juan Island, Washington, the European slug has become much more common than the banana slug.
You can help by staying on trails, watching your step and putting logs and rocks back where you found them.
There is no IUCN Red List assessment (GBIF's IUCN checklist lists the species as Not Evaluated). The main documented concern is competition with the introduced European slug Arion rufus, introduced within the last century; surveys in San Juan Island National Historical Park over four summers (reported by the NPS in 2018) showed it becoming more frequent than the native species at some sites, possibly linked to drought, and researchers are investigating how climate change may affect both.
Natural predators include raccoons, garter snakes, waterfowl and salamanders, with shrews and moles taking juveniles (Redwood National and State Parks). Olympic National Park encourages visitors to stay on trails and to replace rocks and logs, which shelter forest-floor animals.
Did you know?
Banana slug slime helps keep birds away.
Banana slug slime can numb the mouth of a predator, which helps protect the slug from birds.
Olympic National Park describes the slime as a defense that numbs a predator's mouth, protecting against birds.
Amazing facts
-
A banana slug's eyes are on the tips of its feelers.
The two long upper feelers of a banana slug have tiny eyes at their tips that detect light and movement.
Tiny eyes at the tips of the upper tentacles detect light and movement (National Geographic).
-
Banana slugs can climb trees!
Banana slugs are usually on the ground, but they can climb as high as about 20 meters up into trees.
Found on the ground and up to approximately 20 meters above ground in trees (The Evergreen State College key).
-
The banana slug is a university mascot.
The banana slug is the official mascot of the University of California, Santa Cruz.
An icon of the Pacific Northwest, the banana slug is the official mascot of UC Santa Cruz (Olympic National Park).
-
Banana slug slime helps keep birds away.
Banana slug slime can numb the mouth of a predator, which helps protect the slug from birds.
Olympic National Park describes the slime as a defense that numbs a predator's mouth, protecting against birds.
Words to know
- mollusk
- a soft-bodied animal such as a snail, slug, clam or octopus
- decomposer
- a living thing that breaks down dead plants and animals
- hermaphrodite
- an animal that has both male and female parts
- radula
- a ribbon of tiny teeth that slugs and snails use to scrape food
- temperate rainforest
- a cool, very rainy forest, like the forests of the Pacific Northwest
- invasive
- a living thing brought to a new place where it causes harm
Discovery challenge
-
What does a banana slug eat?
Which of these does a banana slug eat?
Which describes the banana slug's role in the forest food web?
- Leaves, mushrooms and dead plants
- Fish
- Rocks
Show the answer
Leaves, mushrooms and dead plants
It eats leaves, mushrooms and dead plants.
Leaves, mushrooms, lichens and dead plant matter, which makes it a decomposer.
A detritivore of plants, fungi, lichens and dead matter that helps cycle nutrients.
-
Where are a banana slug's eyes?
Where are a banana slug's eyespots?
Where are the banana slug's light-sensitive eyespots?
- On its tail
- At the tips of its upper feelers
- Under its foot
Show the answer
At the tips of its upper feelers
At the tips of its top feelers.
At the tips of its two long upper feelers.
At the tips of the upper tentacles.
-
What helps a banana slug slide along?
What helps a banana slug move and stay damp?
Which functions does banana slug mucus serve?
- Wheels
- Feathers
- Slime
Show the answer
Slime
Slime! It slides on its slime.
Its slime helps it glide, keeps it from drying out and even protects it from birds.
Locomotion, water retention, respiration and defense against predators.
-
Where does the banana slug live?
Where does the Pacific banana slug live?
What is the range of Ariolimax columbianus?
- Damp forests near the Pacific coast of North America
- Dry deserts in Africa
- Icy Antarctica
Show the answer
Damp forests near the Pacific coast of North America
In rainy forests near the Pacific Ocean.
In damp coastal forests from central California to southeast Alaska.
Temperate rainforest from central California to southeast Alaska, from near sea level to about 1,370 meters.
Places where you might see it
-
Watch
Country
United States
The United States is a large country in North America made of 50 states, from icy Alaska to the warm islands of Hawaii. It has the Grand Canyon, the Mississippi River and Yellowstone, and about 342 million people live there.
-
Watch
Country
Canada
Canada is the second-largest country in the world, stretching across the north of North America from the Atlantic to the Pacific and up into the Arctic. It has the Rocky Mountains, thousands of islands and about 42 million people, who speak English, French and many other languages.
Explore next
-
Watch
Animal
Garden snail
The garden snail is a land snail with a brown-banded shell about 3 centimeters wide. It glides on a muscular foot over a carpet of slime, comes out mostly at night and after rain, and eats almost any garden plant. It first lived in western Europe and around the Mediterranean, but people have carried it around the world.
-
Watch
Animal
Common earthworm
The common earthworm digs deep tunnels in the soil and comes up at night to drag fallen leaves down to eat. It breathes through its damp skin, has red blood and five pairs of heart-like pumps. Its tunnels and droppings help keep soil healthy.
-
Watch
Country
United States
The United States is a large country in North America made of 50 states, from icy Alaska to the warm islands of Hawaii. It has the Grand Canyon, the Mississippi River and Yellowstone, and about 342 million people live there.
-
Watch
Country
Canada
Canada is the second-largest country in the world, stretching across the north of North America from the Atlantic to the Pacific and up into the Arctic. It has the Rocky Mountains, thousands of islands and about 42 million people, who speak English, French and many other languages.
-
Watch
Animal
American lobster
The American lobster is a big crustacean that lives on the rocky sea floor of the northwest Atlantic Ocean. It has two very different claws, one for crushing and one for tearing, and it must climb out of its hard shell again and again to grow.
-
Watch
3D
Animal
Antarctic krill
Antarctic krill are small, shrimp-like crustaceans about 6 centimeters long that live in the icy Southern Ocean around Antarctica. They gather in enormous swarms, and almost all the bigger animals of the Antarctic, from penguins to blue whales, depend on them for food.
-
Watch
Animal
Army ant
Army ants hunt together in giant swarms and never build a permanent nest. This page is about the best-studied kind, Eciton burchellii, of Central and South American forests. Each night of its traveling phase the colony moves, and the workers link their legs to build a living camp around their queen and young.
-
Watch
3D
Animal
Atlantic blue crab
The Atlantic blue crab is a swimming crab with bright blue claws and back legs shaped like paddles. It lives along the Atlantic coast of the Americas, especially in bays where rivers meet the sea, like the Chesapeake Bay. A mother crab carries up to two million eggs in a spongy orange mass under her body.
For parents & teachers
What children will learn
- Describe the banana slug's body, including tentacles, mantle and foot.
- Explain how slime helps a slug survive.
- Explain what a decomposer does and why it matters to a forest.
- Understand how an introduced species can affect a native one.
Recommended ages: 3 to 17 · About 15 minutes
Talk about it
- Why might a slug need damp weather more than a snail does?
- What would a forest floor look like without decomposers?
- How could scientists find out whether the European slug is pushing out banana slugs?
Try at home or in class
- Lay a ruler on the table and mark 26 centimeters to see how long the biggest banana slugs can be, then compare it with a banana.
- Slide an ice cube across a dry plate and then across a wet plate to feel how a slippery layer helps something glide, like a slug's slime.
Key vocabulary: mollusk, decomposer, hermaphrodite, radula, temperate rainforest, invasive
Where these facts come from
- GBIF Backbone Taxonomy and GBIF Occurrence Search , Global Biodiversity Information Facility (CC0 1.0 (backbone); occurrence counts are facts derived from records under CC0, CC BY and CC BY-NC)
- Slugs of Olympic , Olympic National Park, U.S. National Park Service
- Comparative Ecology of the Native Banana Slug and a Comparably-sized Invasive Slug in Washington State (2018) , U.S. National Park Service
- Banana Slug & Millipede , Redwood National and State Parks, U.S. National Park Service
- Ariolimax columbianus (Gould, 1851) Pacific Banana Slug , The Evergreen State College biota key (hosted by the University of Utah)
- Banana slug , National Geographic
- Wikidata , Wikimedia Foundation (CC0 1.0)
- Wikimedia Commons , Wikimedia Foundation (Per file: Public domain, CC0, CC BY or CC BY-SA only (credited on each page))
Checked, not yet human-reviewed. Last updated October 27, 2026. Spotted a mistake? Tell us.