Taking Time to Look Closer

The following post was written by Woodlore’s Aspirant Instructor and Quartermaster, Keith Whitehead:

Woodlore Aspirant Instructor Keith Whitehead

Woodlore Team Member Keith Whitehead

During our many months spent in the field, we have the chance to see much wonderful wildlife and most of it is a joy to behold. There are some exceptions to this rule however, and racing its way to the top of most people’s lists of unwelcome visitors is the humble slug.

At this point you may be expecting me to extol the edible virtues of this creature in order to curry favour for the unpopular pest, but in truth they are best avoided; if you want a meal, put them on a hook and use them as bait. There is more to the average slug than meets the eye though and a recent encounter prompted me to investigate a little further.

On seeing a slug gently pulsating its way towards my mug, I would normally remove the slug/mug and think no more about it, but this time I decided to see how it used its two pairs of tentacles to locate and recognise food. I knew that the upper pair of optical tentacles were sensitive to light but that they did not recognise colour and that the lower sensory tentacles recognised chemicals in much the same way as our sense of smell. To test this I presented the slug with some food (the closest thing to hand being a biscuit) and watched. As soon as the sensory tentacles brushed the biscuit, the slug veered from its course and proceeded to gorge itself. It’s not often that you find out you have something in common with a mollusc.

The feeding slug

Keith’s tea break gets ruined…

The slug in question is a member of the Arion genus, probably Arion ater (black slug) although this is difficult to differentiate from other members of Arion without dissection. Despite its common name, the colour of the ‘black slug’ varies considerably, this example being an orange/brown. Its mouth can be clearly seen in the photograph, the margins looking like a row of blunt teeth. These are not used the chew the food however. The slug is a mollusc and as such, uses a radula to grind its food. This organ is best likened to a tongue made of cartilage and covered with up to 27,000 chitin teeth. This is used to rasp food into the mouth in a backward and forward motion. Black slugs are omnivores and, as well as biscuits, they will eat vegetable matter, fungi, dung and carrion.

A macro shot of the feeding slug

A macro shot of the feeding slug

Watching this animal feed, seeing it close up and reading about its biology and behaviour garnered new respect for an old adversary, and I would advise anyone to delve deeper into things that are normally overlooked. The process of researching often takes you down unexpected avenues and is a joy for those who are interested. I have only touched on a couple of the fascinating things that I learned during my investigations and the purpose of this article is to encourage others to look, observe and research. A good start and aid to identification of terrestrial molluscs can be found at the ID Tools website.

The next time I encounter one of these creatures on/in my mug, shoes, water bottle or face, at least I will be respectfully disgruntled rather than completely outraged.

– Keith Whitehead

6 thoughts on “Taking Time to Look Closer

  1. Sarah

    Last year was the worst I have ever known for slugs- Some absolute monsters. We once counted 32 at once on the inside of one of the tents! I well remember the slug incident mentioned above by my mum- really quite horrible, but i still quite like watching them. I dont know about slugs, but it was an old treatment for burns to put a snail on them- it is quite cooling and supposedly the slime has some antibacterial properties, but slugs and snails can both carry salmonella and various parasites so perhaps its not the best idea!


  2. Rob Houghton

    Working in the Beacons leading outdoor activities years ago, I used to regularly find a slug (I’m sure it was the same one) in my mug in the morning. This, however, despite my leaving the lid on. They must have stretched themselves incredibly thin in order to squeeze through the hole for drinking – no more than the diameter of a worm. Now that’s dedication to a cause. Still disgusting though.


  3. Paul Shakesby

    Last year, possibly due to the weather, there was what could only be described as a slug plague! So bad it made a ground dweller like myself utilise a hammock in the uk (when we all know they are for jungles).
    This I could cope with, but it certainly stopped me getting the mrs out last year under the tarp, it was depressingly tents all the way.
    Here’s hoping for sunnier times this year.
    Very informative article though Keith, and really liked your real time experiment into slug behaviour. It shows biscuits have special powers I feel!


  4. Catherine Day

    Sarah describes finding one on her face while snug in her sleeping bag, and in her half-asleep state did not recognise immediately that it was a slug rather than a stray bit of hair. She tried to push it out of the way with her tongue. Hmm.


  5. Steve Bayley

    On a Woodlore Applied Bushcraft course in the Brecon Beacons a few years ago I woke up to discover two slugs doing something unspeakable on my spoon inside my mug. Your post about slugs is very interesting Keith, but you are not going to win me over. I’m with Rik on this one; bring on the Hedgehogs!



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