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Image Copyright to RHS/Sian Tyrrell

Slug It! Mapping UK Slugs

Estimated time:

40-45 minutes per session



School term:

All Year Round

Level of Experience:

KS 1-5 – no experience required


Biology, Geography and Maths

Image copyright of RHS/Sian Tyrrell


Explore your school grounds to find areas of different habitats including where slugs are often spotted, to help plan where your route will go. Examples include playground areas bordering on grass or near to edible crops or compost heaps.

We suggest you look over the recording form before your transect walk. This will help you plan which additional information you might like to collect when counting your slugs.

Equipment needed

  • Torches (if dark)
  • Wet weather gear
  • Recording form
  • Pencils
  • Meter measure wheel or map
  • Your selected garden route

Extended equipment list: (See step 6, hints and tips)

  • Conchological Society Slug Identification Key
  • Rain Gauge
  • Thermometer
  • Humidity meter
  • Soil moisture detector
  • Soil testing kit (for testing soil pH)

Help the RHS Plant Health team by investigating and counting the number of slugs living in your school grounds. This is a great activity for your gardening, after school or STEM club, or as part of a science lesson.

Learning Objectives:

  • Learn about slugs, what they eat and their preferred habitats
  • Work scientifically to collect data on the number of slugs in your school grounds
  • Understand how to use transect walks to measure distribution

Step by step guide

Slugs damage plants and crops in gardens every day. Through this activity we are inviting participating schools across the UK to help us map slug populations and understand more about whether climate and geography affect their numbers.

To map the slugs in your school grounds you will need to count the number of slugs you find on a set route. The best time to find them is in the first two hours after sunrise or at dusk in the winter months, towards the end of the school day. During the daytime slugs shelter underground and in the rims and on the underside of pots and containers so you will need to investigate and be more observant.

  • Determine your transect walk by using a meter measure wheel or mapping app/website to plan an 800m route around your school grounds, preferably passing different habitats and plant types. If you do not have enough space in your school grounds for the walk, contact us for advice at slugit@rhs.org.uk.
  • Mark out your transect walk route in the schools grounds or draw a scale plan of the route to follow as a map.
  • Decide when you will carry out your slug counts. We recommend once a week for six weeks or alternatively once a month for at least six months. However counts can be carried out more or less often if you wish, and even a one off count can be added to the UK map! When carrying out slug counts you must record the time of the counts on the recording form, each time you upload your data.
  • Walk your route at a slow pace so that it takes 20 minutes to complete. Search 1 metre either side of you and count any slugs that you can see. Record the number of slugs you count onto the recording form.
  • Submit your recording form and your data will be uploaded to an interactive map so that you can see how your findings compare to those of other schools.
  • Why not go a step further by collecting the slugs you find and try to identify them using this helpful key. When identifying slugs, please use the correct scientific name for them on your recording form.

Hints and Tips

  • Make the experiment more scientific by recording the environmental conditions at the time of measurement. For example temperature, rainfall and humidity.
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