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Saturday, 2 June 2012

Thinking about slugs and snails

Rule 1 of being a naturalist: the most interesting questions are your own questions!

These are some random thoughts about snails that were left over from the book.  Waste not, want not!

Snail home.
Slug home.
I was inspired by the fact that I have had a snail living in a jar on my desk since the start of the year.

If you read my book, Australian Backyard Naturalist, you will learn that the shot on the left is of a slug that lived in that jar for ten months, given regular feeds of lettuce, spinach and bok choy, before I let it go. The photo on the right shows a snail with a damaged shell that has been living in the jar since the start of 2012.

I don't want to let it go, because, with a big panel of shell missing, it won't last long, so I am waiting to see if it can repair its shell.  I don't think it can.

You may like to try conducting some snail races.

You might like to try using light or dark to get snails to go in a single direction, or you might like to see if snails can be attracted by a favourite food—assuming you can identify the favourite foods of snails!

Some foods you might like to try: basil, lettuce, almost any young and tender seedling shoots. Try planting three or four types of seed in a single tray. After a week, when the seedlings are shooting nicely, add several snails, cover the tray, and then come back the next morning to see which seedlings were eaten first.

Be careful not to jump to conclusions until you have tested a few other possibilities!

I have a theory that some hairy or spiny leaves may be less attractive to snails and slugs. Can you test that?

Are snails faster than slugs?

Snails come out when it rains
This makes them excellent for rainy day investigations like these:

To observe snail movement, put a snail on a piece of flat glass, and hold it up to look from below.

To record snail trails, you will need a snail, a clean sheet of paper, and a supply of pepper. Put your snail in the middle of the paper, and leave it alone. After a while, the snail will start to travel across the paper. If there is a slime trail, sprinkle pepper on the trail before the slime goes hard.

Can you invent snail art?

How do snails react when they cross the slime trail of another snail? Does the age of the trail make any difference to the way they react?

How long does it take for a slime trail to go hard?

How many days does a trail last?

Where does it disappear to?

You may care to see whether you can get a slime trail like those of land snails from slugs and marine shellfish. I have never tried this: I predict that marine shellfish do not make a slime trail, but that slugs do. Perhaps you might like to work out why I think this, and then test it.

What use would a snail trail be to a predator? From this, can you make some predictions about the smell or taste of the slime trail? How would you test your predictions? Do so.
These shells were all attacked by predators that bored the shells.

You will need a large supply of bored shells of one species of seashell. Examine the shells to see whether the boring predators go for any particular part of the shell in a given prey species, or if they just bore at random. You will need to think about how you analyse your data.

As a follow-up, you may need to study the anatomy of the selected species to see what the borers aimed at. Some of the victims are bivalves, shellfish with two shells, which are more distantly related to the snails. Think about where the muscle is thet holds the shells together.

When a garden snail is threatened, it pulls back into its shell and often produces bubbles of mucus. My guess is that these bubbles taste bad or are poisonous, but I have never tried a taste test, and I don't recommend the experiment! Incidentally, snails are edible, but don't eat garden snails, in case one of your neighbours is using some sort of snail poison.

Just watching a snail move can be fun. This one is from the
Margaret River area, and I shot it in late afternoon sun.
Why do so few slugs get eaten? One way to find out might be to try eating a slug, but this is not a good idea. What if it has just eaten snail and slug poison or makes its own poisons (and how can you be sure?). What effects would these poisons have on the wildlife in your garden?

By the way, at least one sea slug, found on New Zealand beaches, carries a deadly poison, tetrodotoxin, but no Australian deadly sea slugs are known. Tetrodotoxin is the same poison found in the Japanese fugu fish and the deadly Australian blue-ringed octopus.

These land snails were all gathered on the Swan River at
North Fremantle.  Take a close look, and see how many
different species I found. I think there are three or four.
By the way, if you click on any picture, you see a larger form.
How does a snail's speed vary with size and weight? Does it go faster at a certain temperature or humidity?

Put ten snails in the middle of a black plastic sheet at night, and make a circle of bricks, with 5–10cm gaps between them, all round the snails. The next morning, check for trails and decide whether snails can see or not? Run the same test during daylight and compare the results. If you learn nothing, does that tell you something?

What senses do snails have? Do they react to sights, sounds, smells, or touch? How can you tell the difference between a snail reacting to the touch of a puff of air and a snail reacting to the smell carried in that puff of air?

If people worshipped the Giant African Land Snail, would this be an escargot cult?

Why don't people worship writers who make bad puns?

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