the leopard in the garden

May 23, 2005

in Natural history

Another installment in Things One Finds Under Rotting Logs. It still surprises me that I lived for decades, including a long childhood (not yet complete) spent thoroughly exploring the yard and neighborhood and its more secretive non-human denizens, before I encountered Limax maximus, the Leopard Slug (a.k.a., Spotted Garden Slug, Great Grey Slug, or Giant Garden Slug).

Slugs are, of course, not hard to come by, especially if you are fond of hostas in your landscape. I found my first L. maximus not under a log or munching a hosta, but moving purposefully (albeit slowly) down the trail in front of me. Although nicely camouflaged with dark brown stripes and spots on a tan background, it was hard to miss at about four inches long. For such a lowly creature, it was quite glorious! How had I overlooked them?

As is my habit, I went straight to the books. I learned that L. maximus is not native to North America, but yet another of the throngs of organisms “brought over by European settlers.” Whew. One envisions armadas of arks making their way across the Atlantic in colonial times. Anyway, the Leopard Slug belongs to the family Limacidae, or keelback slugs. These types actually have vestigial, clear shells encased by their mantles, having not slithered their way so far along the evolutionary path as to have completely lost their shells.

Much of the research that has been done on Limax maximus centers around physiological studies such as neurological responses and olfactory processing. However, I did find a couple of intrepid researchers who were working on something more practical, the development of slug slime into an adhesive. Even better, these were high school students, and they won an award for their work. I’m sure if they stick to it, they’ll make fine scientists one day.

I didn’t find much compelling about L. maximus natural history. The usual slug stuff; they don’t live very thrilling lives. EXCEPT when it comes to sex. The accounts of their mating habits – which I found described as “spectacular”, “remarkable”, and at a minimum “interesting” – piqued my curiousity, and the photographs…well, let’s just say I spent the next few years seeking out slug sex. This, it seemed, was something I needed to see for myself.

Leopard Slugs are hermaphrodites, with each individual possessing schizophrenically-named organs such as an ovotestis and spermoviduct. Reproduction, however, does involve two individuals, which ultimately both lay eggs.

Limax1Courtship (if lower animal foreplay can be called that) begins with a long session of mutual licking. Apparently this stimulates the copious mucous production necessary for the next step. The slug pair eventually suspends from a single intertwined mucous string up to eighteen inches long, heads down, twisting and spinning as if in a ballet. Finally, from the head region, the male organ is extruded from each slug. It’s hardly penile-looking, but rather an opalescent, ice-blue organ which also intertwines as the two exchange sperm in a process that can last up to two hours.

Years went by, and I began to wonder where all these slugs were coming from, as I had still not seen any mating. Then one day I was walking into work and found two Limax maximus suspended from their slime cord right on the post in front of my building, not a place I had thought to look. I took a series of photos, including this one, while I and my appreciative, like-minded co-workers looked on.

Although I run across (or accidently walk upon) these handsome gastropods fairly often, I only witnessed slug love this one time. I’m glad that I decided not to disdain such a humble creature, and remained on the lookout for their amour. I don’t know in what context early U.S. Attorney General William Wirt said, “Seize the moment of excited curiosity on any subject…for if you let it pass, the desire may never return, and you may remain in ignorance.”  I’m sure it wasn’t in reference to slugs, but nevertheless, I couldn’t agree more.

2slugs_3 Left: The resemblance between the Leopard Slug and the Bed Leopard has not gone unnoticed.


UPDATE (right): While walking in a swampy woods today, I found a large shelf fungus (Polyporus squamosus, I think) loaded with Leopard Slugs.  Here’s a 21-slug salute!

Mark O'Brien May 23, 2005 at 10:28 am

Hmm. that's something I have never seen. Sounds like a kinky scene if you ask me… hanging from a rope and bathing in jello and then exchanging reproductive juices. Definitely a scene from Cirque de Soleil!!

Snail's Tales May 23, 2005 at 9:11 pm

Deroceras reticulatum mating

I am presenting an account of the mating of another alien slug from Europe, Deroceras reticulatum.

Aydin May 23, 2005 at 9:13 pm

Lucky you! I am yet to see & photograph Limax mating. You inspired me to have a Slug Week this week at

Donna May 27, 2005 at 12:12 pm

I stopped in to look at your kitty. Kitty – cute. Slugs -ew!

rebecca May 29, 2005 at 12:25 pm

Having never been a big fan of slugs, though fascinated by their size and purpose, I almost skipped this entry. Then I saw the photo of their mating and scrolled back to read. First, thank you for the link to the science project about Slu-glue :-). Secondly, the mating? Incredible. Reminded me of a time my sister and I ran across a pond in early spring that was filled (or so it seemed) with mating salamanders, big ones, and as we watched them swim and spin together, we both agreed it was one of the most spectacularly erotic things we had ever seen. Gorgeous, to boot. I can't say that I think these leopard slugs are either gorgeous, or erotic, but the sight of them entwined is… sweet. And fascinating.

Otter November 9, 2005 at 2:19 pm

Thank you kindly for your informative pictures; I've been hunting around to classify a certain slug species and the most detailed image I've found thus far is – surprise surprise – the one next to the Bed Leopard (although at first I thought it was for size comparison purposes and nearly lost my lunch).

Anonymous May 10, 2006 at 4:39 pm

I got on this site to find out what type of slugs are in my backyard. I at first thought they were banana slugs, but after seeing the pics i do believe they are leopard slugs. The only difference is that most of the info says they are about four inches…and the ones in my back yard are…much longer than that. I don't if it's age that makes them grow so long..or if something about the soil where I live. I live in Idaho…and after my friend made a comment upon seeing one of the large slugs and saying something along the lines of how it looked like something from deep inside a forest…got me wondering why my back yard is so full of these large slugs. any ideas?

Nuthatch May 10, 2006 at 5:14 pm

There is actually a pretty good little field guide to the slugs of the American west — Field Guide to the Slug: Explore the Secret World of Slugs and Their Kin -In Forest, Fields, and Gardens from Southeast Alaska to California (Field). I'm not a slug expert, but I'd say the size and abundance of slugs has much more to do with food supply (plant matter) than soil.

Lisa July 25, 2006 at 10:08 pm

I saw my first leopard slug today- climbing up the window sill of my basement window. What I think is amazing is I live in Newfoundland. How cool is that! It was as long as my hand- over 4 inches for sure. It was clearly leopard on the upper part of its body and striped below. No other ones in site although there would have to be somewhere. We had just finished four days of rain! And normally I detest them eating my hostas, but this one fascinated me!

Nuthatch July 26, 2006 at 7:23 am

They are cool, aren't they? I have a lot of hostas, but it's the little garden slugs that go for them; I've never seen these guys on them.

Elishia August 2, 2006 at 9:32 pm

I live and garden in Southern NJ. Much to my surprise (and delight), I witnessed the courtship and mating of a pair of Leopard Spotted slugs from beginning to end. After the mutual licking, both flared their mantles several times. They then intertwined and spun around quickly as they descended on a string of slime. The most fascinating thing was how their sexual organs appeared, first as flesh-colored tubes that elongated, then I watched as blue fluid flowed down these tubes. The tubes then began to flare at the bottoms and began to intertwine just as the slugs had and they too began to spin and flare out on the sides. When they were done, one of the slugs slunk off into a crag in my stucco and the other ate its way up the slime string. This fascinating event took about a half-hour. I ran into the house to tell my husband, and by the look on his face, he must have thought I was hallucinating!! Glad to have found your site because I thought I might have hallucinated too!

By the way…….I have thousands of tiny holes in my hostas and other annuals. The culprits? Tiny baby slugs!! And… thousands of tiny holes in my sofa arm……bed slug!

flipdoubt August 27, 2006 at 2:03 pm

I was fortunate enough to witness the bizarre mating ritual of leopard slugs several years ago when I was a drug addled youth. I just so happened to be in the throws of a psychedelic experience, (thanks to the halucinogenic mushrooms I'd ingested) when I spotted a leopard slug producing, then descending, his own "mucous bungie". Needless to say, I summoned my buddies, (who were also tripping quite hard by that time) and we proceeded to stare in wonderment as we observed the leopard slugs' bizzare sex act from start to finish. I remember going to school the following monday and attempting to explain what I'd seen, (complete with drawings on the black board) to my biology class. It was perhaps the most amazing thing I've ever seen in nature… and I'll never forget it.

Jersey Dave August 29, 2006 at 2:31 pm

They kill plants and eat pepper plants, parsey and the lawn. Kill them all. I throw any ones I find in salt water.

Jim Douma November 5, 2006 at 12:39 am

I live in Edmonds Washington, just north of Seattle, in a fairly wooded area. There are six types of slugs and 2 types of snails in my garden. I was curious about the leopard slug, because, although I wish to keep slugs at bay, I didn't know for sure what they ate. For example, our native banana slug, six inches long, only eats decaying leaves etc. and is not a garden pest. The main menace to my hostas is, I believe, pill bugs, which eat tiny holes in the leaves, not slugs. although slugs will gobble them up if not controlled. I assume the leopard slug is a real garden menace, but I would be much kinder to them if I found they were not.

Anonymous November 14, 2006 at 11:35 am

i'm researching leopard slugs for a portfolio peice in my seventh grade science class. any info.would be great. THANKS!!!

Gwenneth Hindhaugh March 6, 2007 at 5:28 pm

Hi., I live in South/east Australia (near Camperdown, Victoria) and have the pleasure of house guests, ie limax maximus – spotted leopard slug. At first they were mostly under the sink, near dishwasher, but now leave their tell tail marks all over a granite bench. They must go, but how? I have heard they are GOOD in the garden only eating dry, rotted material – is this correct? I sometimes come down in the night and catch the odd one and toss it outside. Any information and advise would be appreciated.
I like your sense of humour.
Yours Gwen H. An Aussie friend.

Nuthatch March 7, 2007 at 7:13 am

Hi, Gwen. The slugs eat plant material, fungi, pet food left sitting out, decaying matter, all sorts of stuff. I don't know if they could be considered good in a garden, but if you don't find major damage to anything, then they aren't bad either and can be left alone. They are not troublesome in mine. If they are getting in your house, you must have some way for them to get in and some rotting wood or something, so you should check that out, as that sounds like a bigger problem than the slugs! Good luck!

Fred April 26, 2007 at 4:26 am

I live in Central England, Europe. Please dont kill them…. and this comes from a meat eating, vermin murderer! Leopard slugs dont eat plants or only when desperate. Some fungi. But I have reason to believe they are actually the gardeners friend, and are cannibal (well not strictly so in that they dont eat other leopard slugs but rather other slugs, the baddies for plants). All my life as a child of horticulturalists and a gardener myself I have killed slugs routinely, however since my last house move to a garden with leopard slugs I have no other slug problem. They are wonderful and I feel privilged to have them in my garden, and pleased each spring when I spot them.

Nuthatch April 26, 2007 at 5:42 am

Thanks, Fred. I like them, too. I have tons of various slugs in the yard, but so long as they have rotting wood and compost to stay happy in, they stay away from my garden plants.

Ashlee M August 10, 2007 at 9:34 am

This was not very help full you should but links to sites that can help cuz i just got a spotted leopard slug in my garden and we are trying to take care of it but how can we with no information

Nuthatch August 10, 2007 at 10:11 am

Ashlee. This is not a how-to guide on taking care of wildlife. Just let the slug be in your garden. It will take care of itself.

Sheryl October 8, 2007 at 5:32 pm

any ideas as to why I have slugs in my dishwasher? any ideas how to keep them out of my dishwasher? Not the greatest place to find slugs, I must say!

Gisela Bach October 23, 2007 at 3:21 am

after finding my first large slug in my composter feasting on apple peels, I used Google get more information about this species. Your page was one of the sites I found quite useful to read. Our garden is located in Toronto, Canada.
I have published two pictures on my blog
My slug I believe is a "Giant Gardenslug" Limax maximus?? Or is it a spotted leopard slug??
cheers Gisela

Nuthatch October 23, 2007 at 8:45 am

Those are two names for the same creature: Limax maximus is the scientific name.

Lisa October 28, 2007 at 7:13 pm

Me again- after seeing my first one last summer, our family has seen them many times. In September we counted 9 in our front yard! In early spring this year I found three that must have hibernated under a board beside our shed. They were all huddled together and looked pretty content. Have yet to see any mate but given the numbers on our property- they're doing it somewhere! Interesting to read they eat fungi (we have some), rotted wood or decaying leaves. Our backyard is fenced in by Cedar hedges with a wood lot in behind. Lots for these slugs to eat! Any idea of their lifespan?

Sis June 23, 2008 at 5:14 pm

i would like to know all the types of slugs because i found one in my yard that is yellow and green and it has a design that looks like it has some eyes and a mouth

Tebedo's June 24, 2008 at 11:27 pm

We live on the eastern edge of Nebraska and we too have been suddenly visited by Leopard Slugs. We have had them now for 3 summers and have never seen them prior to that. They are multiplying as we are now starting to see younger much smaller slugs out with the adults. I've been reading some on their mating rituals and have yet to witness any. Typically they seem to leave each other alone. Our biggest question is what damage can they do? We think they home in the Tiger Lily patch we have and they don't seem to stray far from our front yard. We've not seen any damage to the plant life, along with the Lilies are some Hosta but they are thriving too. I've read a great deal on how to get rid of them but as of yet we've not seen a real need to. So my question is are they harmful at all or are they mostly just a nuisance to most people and this is their reason for exterminating? Do they die off in winter or do they hibernate and return the next year?

Nuthatch June 25, 2008 at 6:44 am

As I mentioned further up the comment thread, even though they are large, I've not seen any damage attributable to them in the garden. This genus strongly prefers fungi (see the photo at the end of the post with them gathered on a large shelf fungus). They'll eat other rotting plant material, and I believe the only live plants they'd eat would be pretty incidental.

They can live up to three years.

berkley May 18, 2009 at 8:29 am

Just found one of these huge slugs yesterday, didn't know what it was. We were amazed by it size! 4 inches+ when it was moving. We live in Gander,Newfoundland and was wondering if it was something new here. My parents were big into gardening back in my home town but no one ever saw anything like this. I found it under a piece of wood along with many other insect species.

Callie August 16, 2009 at 1:21 pm

I have an infestation at my house. I walked outside about 11 o'clock last night and found a total of 9 slugs on my house and garage. There were 2 set of mating slugs. They gross me out.

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