The physics of slugs

By Marcus Wilson 19/05/2011

At Tuesday night’s Cafe Scientifique, we had a very entertaining discussion, led by Mike Wilson from AgResearch, on that most cute and cuddly animal, the slug. Let’s face it, in terms of looks and popularity, the slug doesn’t have a lot going for it, but it’s certainly a very interesting creature.

I learnt a fair bit about its biology, but the most interesting bits for me were the physics. For example, how slugs move is a good example. They create waves that travel down their body – the bits of the slug that contact the ground then push the slug along. If you look at the photo of the underneath of the slug-on-glass, on the handout here, you’ll be able to see the wave pattern on the bottom of the slug.

Then there’s slug navigation. Slugs have homes, apparently, which they will return to after their foraging runs around dawn and dusk.  How do they navigate their way back?  I wondered whether it was scent, but, according to Mike, it might well be by magnetic field. Wow.  I knew some birds did that, but the slug? Clever little creatures.

But the physics isn’t all in the slug’s favour.  There are a few physics based weapons of mass slug destruction out there for the gardener’s use. The slug electric fence sounds an exciting one. Just two strips of wire, separated by an insulator, and wired to a battery. The sluggy crawls over them, and completes the circuit between the two, and gets a shock. That’s usually sufficient to knock them off the wire. However, Mike commented that some slugs can get stuck across the two wires and get fried. Not very nice for the poor molluscs. Some slug fences are just single-wire based – you can use the ground as the other wire – so if the slug is in contact with both the wire and the ground it will form part of a circuit and get a zap. It was suggested that we don’t even have to wire-up the fence – the slugs will get a shock off just a piece of copper wire due to electrochemical effects – in a similar way to the way you can get a small shock if you start chewing tin foil and have amalgam fillings.

But, in my experience, by far the best and most bizarre slug zapping machine is simply the yoghurt-pot filled with beer. Slugs love it, and drown happy.


0 Responses to “The physics of slugs”

  • A biology-related post? We will turn you to the dark side yet, young paduwan 🙂
    But seriously – that’s a lovely post, Marcus!

  • Slug navigation by magnetic field. LOVE it. Lol! I’m just wondering how LONG does it take back them to get home?

    Nudibranch. *giggle*

    Speaking of nudes…you have to excuse me. I’m a little slap happy and must really get some sleep. I was up all Saturday night waiting for the Rapture-That-Wasn’t

  • Hello eviltwit, you’re a night-owl 😉

    That sci-fi list on your blog is long…

    I’d say there is some overlap with my tiny sci-fi collection, but there would have to be with a list that long! 🙂

  • Hey Grant:) Yes, I am a hoot. Heheheh. Sorry, had to:) Doesn’t help that my partner is one, too! We’re both still up. I meant to do my German hmwk for my class tomorrow night roughly six hours ago, but then I ended up watching Sesame Street clips on YouTube – lol (they had some things back in the 70’s that totally would have gone over a little kid’s head!), so the productive part of my night just slipped away. One on YouTube, I just start piggy-backing!

    So, you took a peek at the list, huh? I was thinking of linking the books to their Amazon counterparts so I wouldn’t have to write a blurb about each of them, but obviously that is never going to happen. I love having a personal library – especially since I always have more female sci-fi/fantasy authors than the library or bookstores!

  • Oh, the end of the world. I forgot about that. Too busy looking for houses to buy. Did I miss much?

  • eviltwit – Ursual Le Guin is one of my personal favourites 🙂

    Marcus – you didn’t miss much; bit of a non-event really. (Either that or it’s happened & we’re the ones Left Behind LOL). What I want to know is, when is Mr Camping gonna front up & apologise? He’s certainly stuffed up enough people’s lives.

  • Marcus: Well, other than a lot of suckers gave their belongings and money away in preparation. No. There was general hilarity going on in my house, though. (I did post about it. I had no idea so many people would be looking up NZ and Rapture and 6pm. More people were worried about that than I originally thought.) Good luck with the house hunt!

    Alison: My favorites are Tamora Pierce, Elizabeth Moon, Connie Willis, Marion Zimmer Bradley, Terry Pratchett, Raymond E. Feist and Guy Gauvriel Kay and Jasper Fforde:)

  • Pratchett, oh yeah!!!! And I have equal enthusiasm for GGK – the first of his I ever read were the Fionavar books & I have to say that they remain my favourites.

  • I don’t know of most of the authors on your list – just haven’t time to explore books as much as I’d like to. I’m guessing I’m lean towards “hard” sci-fi though. Loved earlier Greg Bear; have read some Gregory Benford’s; etc.. Not usually keen on fantasy unless is particularly good or has some other twist to it. Pratchett is in a unique genre of it’s own in some ways. I think I’ve read everything except very recent stuff (waiting for them to hit the library or second-hand) and his kids’ stuff.

    The one Elizabeth Moon I have is speed of dark, picked it up in the annual 24-hour sale – mostly because Jennifer Rohn told me it features a bioinformatics scientist! (Still haven’t found time to read it, so no spoilers, please. Still haven’t gotten a copy of Jenny’s book that also features a bioinformatics scientist; J. suggested I might prefer her portrait of a bioinfo. scientist over Moon’s.)