VIDEO: Invasion of the summer slugs

An up close photo of a brown, orange Spanish Slug making its way over yellow and green moss

Spanish slug in the garden (Katie Wells)

Sometimes during summer mornings as I let my dogs out in the backyard, I like to soak in the cool air and poke around my garden. This year, as spring turned into summer, I noticed slime trails glossing over the bricks surrounding my flower beds and holes in the leaves of my irises. I knew we had some snails and slugs, but these were big chunks missing! At first, I thought, perhaps the gnawed-on plants were the result of a weasel or rabbit. As the season progressed and my purple irises did not bloom, I started to suspect a new culprit.

One night my spouse was calling the dogs back into the house when I heard a curious “Woah! Katie come see this!”

I rushed downstairs excited to see what he’d found. Multiple giant slugs were scrunching their way over the threshold of our backdoor. We grabbed our shoes and turned on our phone flashlights: “Time for slug hunting!”

Two leopard spotted slugs are stretched out long, crawling up a light brown, wooden doorframe.

Slugs on doorframe (Katie Wells)

I suspected we’d find a few more; however, we both began a dance of avoidance as we made our way to the garden, trying not to squash the dozens of slugs. Orange-brown, black, leopard spotted! We peered between the leaves of our irises, gladiolas and periwinkles and found them clinging to stems and chilling on the buds. No wonder the flowers hadn’t been as abundant. Every nook and cranny we shone our flashlights into, we found more! We could have been out there all night seeing who could count the most of the slimy creatures.

Grey stone garden stairs with moss covering them and a parade of five slugs on the first step, brown, dark brown and leopard spotted slugs all moving in a line to the right.

Parade of slugs on garden steps (Katie Wells)

That wasn’t the end of the slug fiasco. A few nights later, after we settled in bed, I was petting our husky mix and felt something gooey in his fur. The globs stuck to my fingers and in the darkness, I imagined he rolled in some sort of animal droppings, or worse.

Once the lights came on, I found tiny, white, baby slugs clinging onto my hand. I set them free outside. This slimy discovery led to a new nightly routine of keeping the back door closed and checking his long fur for the little hitchhikers.

More on Slugs:

As summer nears its end, I can safely say that this year there have been a plethora of slugs. So of course, I needed to find out more. It turns out that recent mild winters and rainy springs and summers have caused a resurgence in slug numbers. They have huge appetites and just one slug can lay up to 500 eggs in their lifetime of approximately two and a half years. Some gardeners have even declared war with the slugs.

An up close photo of dark brown soil with white, translucent tiny eggs.

Photo of small white eggs of Slug (123RF)

While pesky, especially to gardeners, all creatures have a purpose. Slugs are gastropods, a type of mollusk essential for returning nutrients back into carbon and nitrogen cycles. They do this by feeding on decaying matter and fulfilling cleaning and recycling roles for the environment. Without them, we’d see a lot of fecal matter, carcasses, rotting vegetables or surpluses of fungi. Therefore, it is best to leave them be. Nonetheless, to save your vegetables, you might consider closing off your crops or welcoming ducks as a new pet, as they are a natural predator of slugs and particularly enjoy eating them.

A colorful picture of three brown and on black ducks in a bright green garden with orange and red wild flowers in the background. The ducks appear to be having a conversation.

Flock of Indian runner ducks in the garden (VERA KUTTELVASEROVA STUCHELOVA (123RF))

While most slugs are harmless, they have a bit of a dark side. There are three main slugs I’ve spotted in my garden this year, the Spanish Slug, the European Black Slug and the Leopard Slug.

The Spanish Slug (Arion Lusitanicus) aka “Killer Slug”

A giant brown slug balancing at the top of a flower stem, a purple sunset in the background

Spanish slug climbing flower (Katie Wells)

A bright orange slug munching on a large bright green dandelion leaf

Spanish slug eating plant (Katie Wells )

A orange-brown slug crawling over dark brown mulch in a garden

Spanish slug crawling on mulch (Katie Wells)

The Spanish Slug is one of the most common species in central Europe and despite its name, did not originate in Spain. These slugs are brown with an orange tint. Because it multiplies so quickly, Germany has ranked it among the “100 of the worst” invasive plant and animal species. While harmless to humans, these slugs could be featured in a horror movie ringing true to their nickname “Killer Slug.”

Most slugs are omnivores feeding on plants and decaying matter; however, these super-sized slugs have been known to eat birds and attack nestlings in a brutal way. Because Spanish Slugs secrete more slime than normal slugs, they don’t have as many natural predators to keep them at bay. The good news, English Blackbirds have recently learned to feast on them. They’ve mastered a technique of picking up the slugs, wiping their slime on the grass, dropping them again, picking them back up and flying off with them.

The European Black Slug (Arion Ater)

An up close image of an inky black slug crawling over granite rocks, sticks, and leaves.

European black slug crawling over dirt (Katie Wells)

An up close image of an inky black slug crawling over granite rocks, sticks, and leaves stretched out long

European black Slug stretched out (Katie Wells)

An up close image of an inky black slug crawling over grass with his head and sensory tentacles up

European black slug looking up (Katie Wells)

In fashion with their midnight color, these slugs are nocturnal and prefer to come out only at night. They are omnivores, but not “killers” like their cousins. They prefer moist conditions like long wet grass and are a productive member of the food chain with natural predators such as hedgehogs, badgers and toads. A study in 2005 suggests that their nutrient cycling helps promote plant species diversity. Like most slug species they are hermaphrodites, meaning they can reproduce on their own if they don’t find a mate.

The “Cannibalistic” Leopard Slug (Limax Maximas) aka “Great Grey Slug”

A grey leopard slug is in a semi circle shape, curving around a circle of moss. it’s evening so the colors in the picture almost look black and white.

Great grey slug on garden wall in the evening (Katie Wells)

A close up of a large leopard slug crawling down the edge of a rocky wall with blue sky in the background.

Leopard slug descending wall (Katie Wells)

Close up of two greyish leopard slugs crawling on wet green moss, a house is far in the background.

Two leopard slugs (Katie Wells)

Perhaps the best of all the slugs, the Leopard Slug is pretty to look at, and I noticed more and more of them inhabiting my yard as the population of Spanish Slugs grew. While their nickname is also horror-esque, these slugs are not a harmful species. In fact, they regulate harmful slugs like the Spanish Slug which competes with snails and other helpful organisms.

These slugs are usually forest dwellers, preferring to feast on mushrooms and other decaying organic matter, but when there is a surplus of invasive slug species, they will rise to the call and feed on other slugs and their eggs. Because of the Leopard Slug’s cannibalistic behavior and their unique way of mating, which is reminiscent of a flowering performance piece, the “Mollusk of the Year” board of trustees gave the Leopard Slug the title in 2005.

Searching for slugs in the garden at night can be a fun activity, and while they are creatures most people don’t give a second thought to, they do have some interesting attributes. Here are a few more fun facts about slugs.

Unlike snails who hibernate, slugs do not need to if the weather stays above 5° Celsius.
Slugs are considered right-handed since their organs and breathing pore are oriented to the right side of their body.
They have blue blood.
Slugs poo from their heads through a small area in their mantle, a saddle-shaped structure on the back of their adjoining head.
Slugs have more teeth than a shark, approximately 27,000 tiny teeth.
Slugs smell with their sensory tentacles and can regenerate a tentacle within a few days.