Recently, my family and I took a vacation to the charming, coastal town of Mendocino in Northern California. We wanted a change of scenery and a change of pace and were delighted that this sliver of the state did not disappoint in either area. We will take away many glorious memories from this trip, but the highlight came in the form of a slow, slimy land mollusk that hid amongst the redwood needles on the forest floor during our spectacular hikes: the banana slug! We encountered dozens of these fascinating little invertebrates along our adventures (and all receiving names from my children, like ‘Slimy’, ‘Sluggy’, ‘Sluggy Jr.’, etc.), which inspired me to research and share some unique facts about this charismatic gastropod.
Coniferous coastal forests from Alaska to California are home to eight species of banana slugs; all eight species range in color from bright yellow to gray, white, greenish brown, spotty, and almost black and can grow up to 10 inches in length! Banana slugs are proud (I assume) to possess four tentacles extending from their head: the larger, upper two can see, and the smaller, lower two can feel and smell. The tentacles can move independently from each other and retract if threatened; however, if a tentacle is lost, it can regenerate! Because these mollusks have no shells, they must live in damp, cool environments with abundant shade, or else they will dehydrate, so there’s no better place for them than the floor of a redwood forest. While the redwoods provide the shady, cool habitat that the slugs need, the slugs provide a benefit to their environment as well. Banana slugs are detritivores, which means they feed on dead organic material on the forest floor and convert the detritus to recycled nutrients which enrich the soil. They are able to move along the forest floor, scooping and pooping, with the help of the sticky slime they secrete. This slime serves a few special purposes: it helps prevent dehydration, allows gas exchange for respiration, carries chemical messages (important to homing behavior and mating), and helps repel predators. (Although some predators have figured out if they roll the slugs up in some dirt, they are a little more palatable.)
Now for the really weird stuff: how they mate. Banana slugs are hermaphrodites (possess both male and female organs) and can self-fertilize; however, they usually cross-mate, allowing each slug to both accept and deliver sperm during copulation. Both slugs will then lay clutches of 20-30 eggs under logs or leaf litter and the eggs will hatch in approximately one month, producing slugs that can live up to seven years. But back to the mating, because this is where things go ‘bananas’ (hahaha!). Mating begins with a foreplay ritual where the slugs secrete a thick layer of slime, like a blanket, on the forest floor. They truly take their time during this phase as it can often take hours. They eventually position themselves into a curved yin-yang position, where they remained pressed together for several more hours. When they have completed this epic mating ritual and are ready to settle into post-coital bliss, they are often met with what one might consider a terrifying problem: they’re stuck. To each other. By the genitals. And then they CHEW THEM OFF!!! That’s right, the male organs often swell to a point during copulation that they cannot extricate themselves from each other, and they use the only available tool to them (their mouths) to remove the ‘problem’. Scientists are unsure if they can regenerate the lost organ, but if not, no big deal, they can live a full and rewarding life as a female.
If you’re still reading this (thank you, and sorry!), there are a few more fun pop culture tidbits about banana slugs worth sharing. Many know that the banana slug is the mascot for the University of California at Santa Cruz, but what you might not know is that after years of being the ‘unofficial’ mascot for the school, in 1980 the school’s chancellor decided to change the mascot to the sea lion, as he felt it was a more dignified animal worthy of representing the school (gasp!). This did not go over well with the majority of the students, and after years of ‘slugging’ it out, the chancellor was convinced to change the mascot back to the banana slug, and peace was restored in Santa Cruz. Following the popularity of the newly-minted mascot, local Santa Cruz children urged the California State Legislature to vote to designate the banana slug as the official state mollusk, but unfortunately the governor at the time, Governor Deukmejian, did not share a fondness for our slimy, yellow friends, and vetoed the bill. Regardless, the banana slug has slimed its way into many a Californian’s heart, and this fascinating critter certainly added to the magic of my experience in the redwood forests of Northern California. So, if you are ever in that neck of the woods, I encourage you to watch where you step and spend a few moments searching the forest floor for this unassuming, yet vital, inhabitant of the redwoods.
Photo Credit: By Brynne Mulrooney