by Bob Vergette
Which local creature is almost everyone on Pender familiar with? The Banana Slug, of course! Slugs are members of the Phylum Mollusca, in the Gastropod Class that also includes their hard-shelled snail cousins. Several species of slugs can be found on Pender; however, only a few are native. This includes the Banana Slug (Ariolimax columbianus) - the second-largest slug in the world, growing to 20 cm in length and living as long as 7 years. Banana slugs are olive green with none, a few or many black spots.
While banana slugs can damage plants in moist gardens, they are usually not a problem as they prefer to eat woodland plants. In natural habitats they act as nature's garbage collector and recycler, consuming and further breaking down dead and decaying matter, chewing with their 27,000 teeth on a long tooth-covered tongue. They are mostly nocturnal feeders, eating decaying animals, mushrooms, and plants, and are important in the forest for recycling nutrients back into soil. During the heat of summer, slugs cover themselves with slime, burrow into leaves and soil and go dormant until the rainy season starts.
A cool fact about slugs is that a group of them is called a cornucopia.
If you watch a slug as it moves undisturbed through the forest you will see that it has four
tentacles. The two upright stalks on the top of the head are eyes (photoreceptors), which
distinguish changes in light and movement. Low to the ground are two more tentacles, which the slug uses to feel its way as it moves along. On the right side of the slug’s mantle is a hole known as a pneumostome; this is where air passes through to a simple lung-like organ.
One thing all slugs have in common is slime, and the banana slug is no exception. They use it for protection to keep their bodies moist, and as a slick yet sticky surface that makes traveling on their muscular foot that much easier - and speedier! They can move on their slime trail at 17 cm per minute. At a molecular level, slime is a highly organized material that can absorb up to 100 times its original volume in water. This property is readily apparent should you ever make the mistake of trying to rinse slug slime from your fingers: slime begets more slime. It is best to wait for it to dry and then roll it off, as you would rubber cement. Slug slime also has an antiseptic property that will numb your mouth should you for some reason decide to lick it off your fingers. It is reported that First Nations used the slime to numb toothaches.
Slugs are hermaphrodites, which means they have both male and female sex organs, but they normally still need two to mate. They find each other in the forest by laying down slime that contains pheromones which attract other slugs. Banana slugs lay 20 to 30 small eggs under logs or leaves; the eggs spend winter in the ground and hatch the following spring. Young slugs disperse from the nest and find their own home range, with a good supply of food and shelter. Newly hatched slugs are tiny, but voracious. Slugs mainly feed at night and on wet, cloudy days. During the day, they retreat to dark, moist sites under plants, decaying leaves, pots and other objects.
Other species of slugs commonly seen on Pender are the European black slug (also known as the licorice slug), the European great grey slug (or leopard slug) and the grey garden slug. The great grey slug of Europe is a large voracious garden pest and will not only devour many plants but will also stalk and eat other slugs. European black slugs are also large, reaching up to 12 cm in length. As well as black, they can also be reddish brown or even yellowish orange in colour, but on Pender they all seem to be black. Grey garden slugs are much smaller (up to four cm long), mottled grey or light brown and are very common in gardens and compost piles. Other native species that have been found on Pender include the Reticulate Taildropper (Prophysaon andersoni) and Yellow-bordered Taildropper (Prophysaon foliatum; Laura Matthias, personal communication).
Although these slimy creatures do not seem to be too appealing to consume, they do have predators including raccoons, garter snakes, ducks and geese. Humans can also be predators of slugs, and people will dispatch slugs found in their gardens. We encourage gardeners not to harm banana slugs as they are important for breaking down plant material in our forests. If found in a garden they can be gently moved into natural forest areas.