Tiny shells and hidden animals

Do you like snails? The gastropod molluscs commonly found in your garden are probably the first thing that spring to mind. Or maybe you smell garlic and see a yummy plate of l’escargot.  However, this small word covers an array of species, in fact most gastropods (meaning literally ‘belly foot’) that have a shell into which they retract: whelks, winkles, cockles, razor shells, freshwater pearl mussels and many more species are basically snails! Nigel Buxton, our Natura Project Manager, tells us about the importance of Protected Areas for some of Scotland’s lesser-known land snail species.

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Snail on dune grass, (C) SNH/Lorne Gill

Common land snails come in an impressive range of shapes and sizes – with around 120 species in the UK alone. In Britain the garden snail, one of the largest land snails, is well known especially to gardeners!  There are also white-lipped snails, brown-lipped snails, banded snails, glass snails, chrysalis snails, even edible snails; most of these are less than 2 cm in size.

Now imagine a land snail that can have a shell 20 cm long and 10 cm high; that’s the giant African land snail, one of the world`s largest land molluscs. This is a very successful species, originally from east Africa but now naturalised in many parts of the world where, with the ability to survive down to 2⁰C, it is a highly invasive and damaging agricultural pest.  Thankfully it does not occur in Britain where, as you well know, temperatures frequently fall well below 2⁰C!

This giant snail has often been promoted as a pet, contributing significantly to the invasive non-native species problem:  because it is hermaphrodite, a single individual has the capability to produce fertile eggs – over 1,000 in a single year. In the US the potential for agricultural damage is recognised as so severe it is now illegal to have one as a pet or to bring one into the country.

Our numerous land snail species utilise a variety of habitats and are widely distributed across the countryside, including our Protected Areas. Except where calcium is scarce (essential for building shells), all Protected Areas will support species of snails, from the banded white and brown lipped snails of grassland and hedge banks, to the abundant sandhill and pointed snails found in seaside sand dunes and machair.

In contrast to the giant African land snail, some of Scotland`s most important snails are tiny; these are the whorl snails. Three whorl species live in Scotland – Geyer`s whorl snail, the narrow-mouthed whorl snail and the round-mouthed whorl snail – all of which are less than 2 mm in size!  Desmoulin`s whorl snail, the largest species at 2.6 mm long, occurs only in England & Wales.

These tiny snails have restricted distributions within which they are scarce – although knowledge of numbers and locations is constrained because they are so hard to see!  Nevertheless, their conservation importance is such that they are identified as features on some Special Areas of Conservation (SAC) in Scotland.

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Geyer’s whorl snail, (C) Dr Roger Key

At Garron Point SAC, in Aberdeenshire, the narrow-mouthed whorl snail is the site’s only protected feature. Geyer`s whorl snail occurs on three Scottish SACs in the eastern and central Highlands and may be found alongside the round-mouthed whorl snail. These species apparently flourished in postglacial conditions but climatic change has greatly reduced their range so that they are now known only at widely scattered European localities including northern Scandinavia, the Swiss Alps, to Britain and Ireland. Round-mouthed whorl snails are a protected feature on two of our SACs and a Site of Special Scientific Interest (SSSI).

With innocuous, hard-to-see species like whorl snails that are found at restricted locations and have limited overall range, you can see how vulnerable these animals are. With rapid ongoing climate change it is vital to avoid unwitting damage to these locations and to focus optimum management on those sites we know about. These tiny snails highlight where Scotland`s Protected Areas can be of paramount importance, especially when continued survival is both tenuous and sensitively balanced.

Our network includes more than 1500 protected areas across Scotland that are nature’s special places. Some are nature reserves managed by SNH or charities, but most are privately owned, and most have good public access thanks to Scotland’s Outdoor Access legislation.  SNH plays a key role in looking after these sites and monitoring their wildlife. Do you know where your local protected areas are and why they are important? How many have you visited? For more information on these amazing places visit Sitelink.

Six snail facts

  • Our common garden snails can reach a top speed of about 45 metres per hour (or 75cm in a minute).
  • Snails can see and smell but they can’t hear. Most land snails have two sets of tentacles, the upper ones carry the eyes and the lower ones are used for smelling.
  • Hermaphrodite snails have both male and female reproductive organs, however, they usually still mate with another snail, with both partners laying eggs.
  • Snails have a courtship process for attracting a mate, which can last between 2 and 10 hours.
  • Snails tend to live for between two and five years, however in captivity some can live for up to 25 years.
  • Snails are surprisingly strong and can lift up to ten times their body weight.

Photo Credits

Common chrysalis snail, (C) Christophe Quintin, Creative Commons

Underside of snail, (C) Vicki, Creative Commons

Giant African snail, (C) Malcolm Manners, Creative Commons

Giant African snail mating, (C) Tim Ellis, Creative Commons

Pointed snail, (C) Katja Schulz, Creative Commons

White-lipped snail, (C) Martin Cooper, Creative Commons

Narrow-mouthed whorl snails, (C) Museu Valencia Historia Natural

Narrow-mouthed whorl snail on palm, (C) Dr Matt Law

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