Snails 'have a homing instinct'

BBC News, By Pallab GhoshScience correspondent, 3 August 2010 Last updated at 16:08 GMT

A 69-year-old amateur scientist has apparently discovered that her garden snails have a homing instinct.

Dr Dave Hodgson from Exeter University explains how the experiment works

The result has astonished some professionals who believe that snails are far too simple creatures to find their way home.

So with the help of BBC Radio 4's Material World Programme they have launched a national experiment to settle the question.

The idea for the experiment started last year - when Ruth Brooks became exasperated with the snails in her garden.

They had eaten her lettuce, ravaged her petunias and devastated her beans.

She was too kindly a person to kill them - so she took them away to a nearby piece of waste land. But she found that they kept coming back.

"I really don't like killing snails with pellets or salt and I wanted to find a humane way of protecting my garden," she said.

It is gardener's lore that snails have a homing instinct. But Ruth wondered if there was a scientific basis to this.

For help, Ms Brooks called Material World, who put her in touch with Dr Dave Hodgson, a biologist at Exeter University.

Together they devised a series of experiments to assess the snails' alleged homing ability.

Ruth's results suggest that snails are able to home. She found that her snails were able to return to her garden unless they were placed more than 10m away.

Simple minds?

It was a result that astonished Dr Hodgson: "The conventional thinking is that snails are far too simple to be able to find their way home. So if Ruth's findings are true we'll have to rethink our theories."

It is gardener's lore that snails have a homing instinct

Ruth's result is from just one experiment. In science, researchers try to do as many experiments as they can to ensure they have not got a freakish result - or in Ruth's case - that she has particularly clever snails.

To learn more, Dr Hodgson has invited members of the public to take part in a National "Snail Swap" Experiment.

He is asking people to collect their garden snails in a bucket and label them with coloured nail varnish - a process he says does not harm them.

The next step is to persuade a neighbour and nearby friend to do the same - but they have to label their snails a different colour. The final step is to swap buckets and wait to see if any of your snails come back.

"It could be a long process," says Dr Hodgson, "because snails aren't the fastest of creatures."

Sent packing

According to Michelle Martin, who is managing the project for BBC Radio 4: "Taking part in this experiment is a great way to keep bored children entertained during the school holidays, and you'll be contributing to real science research.

"Even if none of your swapped snails return we'd like you to enter your results online, as the data will help ecologists understand the behaviour of these ancient creatures."

This study concerned only one type of snail, but there are many others. For example, the giant African land snail, which, as an invasive species, has become a serious crop pest in Asia, would cover a much wider territiory than its smaller European cousins.

This means it would have to be taken much further away to ensure it did not come back.

But, currently, we do not know for sure if they really do behave like that Observers say it would be interesting to replicate this study elsewhere to see if there really is a difference between the homing behaviour of different types of snails.

If the results back Ruth Brooks' claims - gardeners will have to do more than just throw their snails over the garden fence to be rid of their pests.

And scientists will have to think again about the now not so humble garden snail.