Science Snapshot: Banana Slug

The term, “love at first sight” is commonly used to describe an extreme liking for someone or something upon first seeing them in person. Usually this term matches with a beautiful woman or a delicious cheeseburger. Well, while camping in the Coastal Redwoods of California, I had truly experienced love at first sight! I exited my tent one moist, chilly morning to behold an incredibly beautiful creature. Its cylindrical, yellow slime-coated body glistened in the morning dew and its probing eye stocks seemed to wink at me. I knew I had found love at first sight! I understand the general public’s opinion of the banana slug does not match my enthusiasm for them… slimy, yucky, and gross might be words commonly used to describe slugs. Well I am here to show you that slugs can be fascinating and beautiful creatures!

Photo by Jay Merrill

Banana slugs, the yellow mollusks pictured all throughout this post, are the largest slugs in North America and the second largest slugs in the world. They are found along the Pacific Coast of the United States in cool, moist forested areas. Slugs can only survive in very particular conditions–it needs to be cool, moist, and there needs to be available food. That is why the banana slug thrives along the Pacific Coast forests. The mild, rainy, foggy, and heavily wooded areas along the North Pacific Coast are just what the gastropod doctor ordered for our banana slug. But what if the weather calls for a hot, dry summer? Well, the banana slug can go through a process called “aestivation” which is basically hibernation during the summer instead of the winter. The slug coats itself with even more mucus, hides under debris, and dramatically decreases its metabolic activity until the ideal environmental conditions become available again.

This hole on the right side of the slug is where its lone lung is located. The hole is called a pnuemostome. Photo by Jay Merrill

The slime coating on the banana slug is more than a chick magnet (it literally does have chemicals in its slime that help it attract a mate!); it also acts as an adhesive so it can climb things, a moisturizer so it does not dry out, and a chemical defense so it can deter predators who try and eat it. Taking an even closer look at the slime, it helps the slug to breathe and travel across the uneven forest floor acting as a lubricant. The slime of the banana slug is made of a special substance that is part solid and part liquid… we call this substance “liquid crystal.” The slug travels using its one foot which moves in a continuous wave-like motion along the forest floor.

These slugs also help the environment! They feed on detritus, which is decomposed organic matter, which recycles nutrients back into the soil and produces nitrogen-rich fertilizer after excretion. Excretion is a nice, scientific way of saying poop or other waste products. Any animal like the slug that does not eat living things and helps recycle the dead things for other living things is a welcome addition to all ecosystems.

A blurry picture of the banana slug eye. Photo by Jay Merrill

But wait, the coolness continues! The banana slug has eyes that can extend and retract. Its eyes are seen as tiny black dots at the end of long stocks. It can move its eyes in any and all directions because it is attached to those long, narrow stocks. This helps them to navigate up a tree, around a rock, or to any other place it needs to go. The shorter sensory organs found underneath the eyes, just between the mouth of the slug, are used for feeling and smelling.

Alright, so maybe that was way more than you ever wanted to know about a slug. Well before you go judging the poor slug unfairly, consider this: The average human produces 6 cups of mucus daily! Perhaps you have more in common with your new friend the banana slug after all.

Photo by Jay Merrill

*To learn more about the slimy slug and how scientists are creating awesome technology inspired by our banana slug friend, check out this video:

If you read this whole blog post, you are my hero! Thanks for reading. Please feel free to leave me a comment and feedback below. Also, let me know if there is any particular science topic you would like me to look at “through green tinted glasses” and I will write about it.


Works Cited:

That Slug Life




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