Homing Limpets

The common limpet (Patella vulgata) is a grazing animal that roams over submerged rocks at high tide eating algae.  Before the water retreats at low tide they return to a favourite spot on the rocks where they will sit all through the low tide period until they are covered by the sea again.

You can prove that this is true with a very simple experiment.  First you will need to collect together your apparatus.  For this experiment you will need, a small pot of enamel paint, cheaply bought from any modelling shop, a small paint brush, a clip board, a piece of graph paper and a pencil.

Find yourself a likely group of "volunteers" by looking at the rocks at your local beach during low tide.  Try to find a group of limpets that are quite close together then using the paint and brush number each of them.  It is easier to use dots like on a domino rather than drawing numbers and just a light blob of paint for each dot will do.  When all the limpets in your chosen group are numbered put your paint away carefully then get out your clipboard, graph paper and pencil.  What you need to do now is try and draw the group of limpets and their position relative to each other.  Remember to number the limpets in your drawing with the same number on the real limpet.

That is all you have to do on this low tide so you need to wait now for the tide to come in and go out again before you can finish your experiment.  It doesn't need to be the very next low tide as this is likely to be during the night.  You can leave it for a couple of days if you want to but not too long as the paint will wear off eventually.  On your next visit to the beach take your clipboard and piece of graph paper with your limpet map on and find your chosen group by going back to the same rock that you chose to start with.  When you have found your group hold up your drawing and tick off the limpets that have safely returned home.  Are they all there?  Usually all the limpets will be back where you left them but obviously the beach is a harsh place to live and a lot can happen in a few hours so if one of your "volunteers" is missing try and have a think about what might have happened to it, has got itself lost, has the weather been stormy so it might have been washed away, are there a lot of birds around that may have eaten it?

As an alternative to drawing the group of limpets, if you have access to a digital camera then this can be used to take a before and after photo.