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I found a snail (pictured above) in my garden carrying an extra shell on its back. How common is this and what is its purpose?

Gerald Legg
Hurstpierpoint, West Sussex, UK

The snail with the extra shell belongs to the genus Cepaea, either a white or brown-lipped snail. It is carrying the broken shell of a garden snail, Cornu aspersum. The damage to the latter looks like it was sustained by a thrush breaking it. The Cepaea must have accidentally picked up the broken shell while moving around.

I haven’t seen a snail carrying an object on its shell before, but underwater I have seen sea urchins carry pieces of shell on their backs, which are apparently .

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