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Activity: tracking tunnel

Tracking tunnel experiment to track species
tracking tunnel
© Setareh Chong

Tracking tunnel experiment

Aims: Tracking tunnels are a non-invasive tool that ecologists can use to investigate the presence of mammals in a habitat by identifying their footprints. Tunnels can be situated along hedgerows or at the edges of fields or gardens. Different food types can be used as bait, the mammals walk over a pad covered in ink to reach the food and then leave their footprints on the paper. Different species leave different footprints, which allow us to identify which species visited the tunnel.

We understand that current restrictions in light of Covid-19 mean that it may not be possible for you to complete this activity – if this is the case, don’t worry but feel free to have a look at how we can use these tunnels to get an idea of the species we might find in our local environments.


  • 2 empty, clean plastic bottles of milk (we used 4 pint containers, but you can use larger ones too). Keep the milk bottle lid too.
  • Black bin bag
  • Piece of paper
  • Food colouring or ink (this should be non-toxic)
  • Clean sponge
  • Small tray that fits inside the milk bottle (e.g. margarine lid)
  • Scissors
  • Piece of wood (or similar to wrap paper around)
  • Elastic bands (optional)
  • Food (e.g. peanut butter, apples, hot dogs, etc.)

How to assemble your tracking tunnel:

Step 1: Cut off both ends of the milk bottle. Do this with both bottles and slide one into the other, so that the ends overlap.

Step 2: Cut the black bin bag so that you have a strip that wraps around the “tunnel” created by the two milk bottles.

Step 3: Wrap this section of the bin bag around the tunnel and tape it, so that the inside of the tunnel is now dark. This is because the small mammals we are looking to study like darker spaces.

Step 4: Take the piece of wood and the piece of paper. Wrap the paper around the wood. The elastic bands can be used to secure the paper to the piece of wood. Slide the piece of wood through the milk containers, so that it is inside the tunnel. This is what the mammals will walk over when they enter the tunnel.

Step 5: Take the food colouring and pour some of this into the tray. Place the sponge on this, so that the sponge absorbs the colouring and when the mammal steps on the sponge its feet will pick up the colouring.

Step 6: Place the food on the milk bottle lid, so that it doesn’t get covered in the food colouring. This food is to attract the small mammals into the tracking tunnel. Put the milk bottle lid containing the food on top of the sponge (which is kept on the tray).

Step 7: Ideally, your tracking tunnel should be situated outside, close to the edge of a habitat, such as the edge of a garden. Set up the tunnel so that you place the wood inside and put the tray on top of this in the middle of the tunnel. Leave the tunnel overnight. You can check each day for footprints. NOTE: make sure the place you choose is out of reach of pets or small children as the small objects in this experiment, such as the milk bottle lid, can be a choking hazard.

peanut butter for tracking tunnel

Step 8: Try to identify the footprints. You may see footprints from hedgehogs, rats, mice, shrews and other small mammals. You can see some of the common visitors to tracking tunnels in the footprints below. The Mammal Society also has lots of field guides to help you identify any footprints you find. You could also take a look at their Mammal Mapper app to help the Biological Records Centre to learn more about the distribution of small mammals across the UK.

Things you can experiment with:

Food type: Different animals are attracted to different foods. You could try varying what you use in your tracking tunnel throughout the week. Do mice like hot dogs, whilst hedgehogs prefer peanut butter?

Location: You could also vary where you put your tunnel. Do more mammals visit your tunnel when it’s placed at the edge of a garden rather than in the centre where it may be more exposed?

You can upload any photos you take onto Padlet to share with other members of the course and or fill in this form for collective data analysis (all data provided on the form will remain anonymous, be used purely for the purposes of this activity and be managed by the Department of Biology).

examples of possible tracks-results

a) Hedgehog paw prints from a tracking tunnel experiment, b) A hedgehog, c) A brown rat, d) Brown rat prints from a tracking tunnel experiment

This is an additional video, hosted on YouTube.

© Rachel Hope
This article is from the free online

The Biology of Bugs, Brains, and Beasts

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