So You Want To Be A Scientist? Homing Snails Experiment: Snail Swapping

The Great Snail Swap by Ruth Brooks


Ruth Brooks and her grandson.

You and a friend will collect, mark and swap snails, then monitor them for one week..

We would like to know: how many snails return home, and how many set up home in their new garden.

Our results will help gardeners to control snails humanely, and will provide fascinating insights into their behaviour.

Our printable booklet contains instructions about the experiment, and a results table for you to fill out. Then you will need to enter the data online for the results to be analysed.

The Great Snail Swap Instructions / Results page(.pdf)

The Great Snail Swap results page(.rtf)

Submit your results

Chris Collins on how to deter slugs and snails


Equipment you will need

The equipment you will need, nail varnish, corrector fluid or waterproof paint in two colours, two containers with high sides (such as large plant pots or small buckets), some snails and a long tape measure.

  • Nail varnish, corrector fluid or waterproof paint in two colours
  • Two containers with high sides (such as large plant pots or small buckets) ) or a lid
  • Some snails (see below for how and where to collect them)
  • Long tape measure





Ruth Brooks and her grandson.

Find a friend or neighbour who is willing to swap snails with you.






Ruth Brooks and her grandson.

If possible, choose a day or evening which isn't too hot (in the heat, snails will be inactive). You will need to collect snails from your own garden (Garden A) and your friend will need to collect snails from their garden (Garden B). They can be found in dark damp places such as the bottom of walls, inside drains, or upturned flower-pots.

You are looking for one species only - Helix aspersa (the Garden snail) - see the box below for how to spot them. You should each collect as many snails as possible, preferably from one area of the garden e.g. rockery or vegetable patch. They're very active at night so you may have more chance of finding them after dark.

The bigger the sample, the more chance there is of some returning, but it doesn't matter if you and your neighbour have a different number.

How to spot Helix aspersa

Two snails. On the left Helix aspersa, on the right Helix pomatia. This file is licensed under the Creative Commons Attribution ShareAlike 3.0 License.

Helix aspersa (also known as Cornu aspersum)

These snails have pale brown shells flecked with white or yellow markings. The mouth of the shell is wide with a thickened white lip. There are 4 or 5 rapidly expanding, slightly convex whorls between the mouth of the shell and the tip. Their body is grey-brown with a scaly appearance.

If you're not sure your snail is the right species, then try this identification guide from the Conchological Society


Ruth Brooks and her grandson.

Paint all Team A snails (from garden A) using one colour, and all Team B snails (from garden B) using a second colour. You can use correcting fluid, nail polish, or paint - but the paint needs to be waterproof. I marked my snails with acrylic paint from my local craft shop, and used cotton buds to put the paint on, but a paintbrush would do.

Remember to wear gloves, or wash your hands after handling snails.


Ruth Brooks and her grandson.

Put Team A and Team B snails in separate containers marked with the right colour. The containers need to have high sides, because active snails can leg it over the top quite quickly. If you are using a container with a lid, make sure that there are air holes in the top. Use a watering can to keep the snails damp, keep them in the shade, and put some tender plants, vegetables or flowers for them to eat in the bottom if they are going to be there for a while. Count how many snails you have collected from each garden and note down the number.


Ruth Brooks and her grandson.

Swap containers so you now have your friend's marked snails. They should have your coloured snails. You can each go back to your own garden for the next stage.



Ruth Brooks and her grandson.

Release your friend's snails in the same area you collected your own snails from. Likewise, your friend should release your snails in their garden. Measure the distance from your release point to the release point in your friend's garden. If it's a long way, you can calculate it online with software such as Google Earth.


Ruth Brooks and her grandson.

You are waiting to see when the first of your coloured snails arrives back in your garden. Note when the first of your snails arrives back in your garden.

A week after release, count all the snails which end up back in your garden. Plus, you should count the number of your friend's snails that set up a new home in your garden.

Even if no snails return to your garden, this is still useful scientific data, and you can enter 'zero' as your result.

Your friend should count how many of their snails returned to their garden, and the number of your snails that stayed put. Also note down any barriers that lie between your gardens.

You can continue to monitor your snails after the first week if you like. But make sure you enter your results online before 31st August 2010 so the data to be scientifically analysed in September.


Ruth Brooks and her grandson.

When you have finished your experiment, enter your results before 31st August 2010.




Follow my research diary on Facebook

I'll be presenting the results at the British Science Association Festival in Birmingham in September.

Remember - it's all in the cause of science. So, happy hunting and have fun!



1. Team name**
2. Name of person A (optional)
3. Name of person B (optional)
4. Your organisation / club / school (optional)
5. Email address 1 (optional)
6. Email address 2 (optional)
7. Distance between release points in Garden A and B**
8. Barriers between gardens e.g. fence, hedge, wall, road, river, gravel, buildings**
9. Weather on day of release e.g. dry, hot, sunny, humid, cold, average, rainy (optional)
10 Number of Team A snails collected from Garden A and released in Garden B**
11 Number of Team B snails collected from Garden B and released in Garden A**
12. Number of snails from Team A found back in Garden A (zero is an option)**
13. Number of snails from Team A stayed in Garden B**
14. Number of snails from Team B found back in Garden B (zero is an option)**
15. Number of snails from Team B stayed in Garden A**
16. When did the first snail arrive back in its original garden?**

**mandatory fields

Submit your results

Entries close at midnight on 31st August 2010

Useful Links

Chris Collins on how to deter slugs and snails


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