Species Action Plans - Desmoulin's Whorl Snail
(Vertigo moulinsiana)
| A very small, 2.2-2.7mm, snail that lives on tall swamp vegetation in summer such as sedges, reeds and reed sweet-grass in wet situations. It is not an aquatic species. |
Click to view the Desmoulin's Whorl Snail Action Plan |
Current Status
National Status
- In the UK, Desmoulin's whorl snail is known from a series of sites stretching in a broad band from Dorset to Norfolk. This snail is listed on Annex II of the EC Habitats Directive, and is listed as rare in the GB Red List.
Norfolk Status
- Present within fen sites in the Yare, Ant and Bure valleys in the Broads Natural Area. Also sites within the river Nar valley (West Acre, Castle Acre and nearby East Walton and Adcocks Common), Glandford on the river Glaven and the Upper Wensum (Shereford, Hempton and Guist) within the North Norfolk Natural Area and Thompson Common in the Brecks Natural Area.
Current factors affecting the habitat in Norfolk
Destruction of wetlands. Habitat degradation, particularly as a result of changes in hydrology and possibly the introduction of grazing.
Current Action in Norfolk
Desmoulin's whorl snail is one of the 'interest features' of The Broads candidate Special Area of Conservation (cSAC), the Norfolk Valley Fens cSAC and the River Wensum cSAC. Works associated with the Fen Management Strategy in the Broads and other fen restoration effort will continue to increase the extent of suitable habitat and bring it into sustainable management.
Action Plan Objectives and Targets
National
- Maintain viable populations of snail across its current range to ensure favourable status.
- Survey to determine the full extent of the snail's current distribution and precise habitat requirements.
Norfolk
- Maintain viable populations within the fens of the Yare, Bure and Ant valleys in the Broads. Also those present on the rivers Nar, Wensum and Glaven and Thompson Common in the Brecks.
Management Guidance
(This guidance is a general summary; for detailed information or advice consult the references or contacts below.)
Desmoulin's whorl snail occurs in long-established swamps, fens and marshes usually bordering rivers or lakes, living on stems and leaves of tall grasses, sedges and reeds, probably over-wintering in plant litter. Inhabited plants usually stand in shallow water or on humid, damp ground and the snail shuns dry fen; the snail will disappear from areas where conditions become dry enough for plants such as common nettle and great willowherb to become frequent.
- The groundwater level must remain close to the surface so that the ground remains at least moist for the majority of the summer period, although limited seasonal drying appears to be tolerated.
- Conversely, conditions must not become so wet that aquatic plants such as water-cress and fool's-water-cress take over.
Ideally there should be no grazing by domestic livestock. Heavy trampling will eradicate the snail and management that reduces or removes tall grasses and sedges is detrimental. - Regular cutting or mowing removes tall vegetation that the snail requires.
- The snail is able to tolerate low intensity, patchy grazing and infrequent cutting although tidy riverbanks will eradicate the snail.
- It has a strong preference for open, unshaded situations although it can tolerate light shade. Scrub, tall trees and tall reed that cast deeper shade are inappropriate and scrub on fens may also result in drying out during summer.
- It is crucial that sites have areas of fen or reed on higher ground to provide refuges when rivers are in flood, as adults floated out of riparian 'hover' during winter flooding do not survive.
- The snail occurs less frequently on common reed, so management that encourages this plant should not be adopted where there is a good population of the snail.
- It has recently been discovered that the snail will occupy and breed readily in translocated and newly-created marsh.
Key Contacts
-
Protected Species Officer
English Nature, 60 Bracondale, Norwich, NR1 2BE
Telephone: 01603 620558 Fax: 01603 762552 Email: norfolk@english-nature.org.uk
References
Bratton, J H (ed) (1991). British Red Data Books: 3. Invertebrates other than Insects. Peterborough, Nature Conservancy Council.
Drake, C M (1997) (ed). Vertigo moulinsiana - Surveys and Studies Commissioned in 1995-6. English Nature Research Report No 217.
Drake, C M (1999). A Review of the Status, Distribution and Habitat Requirements of Vertigo moulinsiana in England. Journal of Conchology, 36(6), 63-79.
Drake, C M (2000). A Review of the Status, Distribution and Habitat Requirements of Vertigo moulinsiana in England. Journal of Conchology 36: 63-79.
English Nature (2001). Desmoulin's Whorl Snail. A rare European snail. English Nature leaflet. English Nature, Peterborough.
Jackson, M J and Howlett, D J (2000). A Survey of the Terrestrial and Amphibious Molluscs of the Upper Wensum Valley, October/November 1999. Report to Environment Agency, Anglian Region, Eastern Area.
Jackson, M J and Howlett, D J (2000). A Survey of the Aquatic Macroinvertebrates, Terrestrial Molluscs and Moths of Guist Common, Guist, Norfolk. Report to Environment Agency, Anglian Region, Eastern Area.
Kerney, M P (ed) (1976). Atlas of the Non-Marine Mollusca of the British Isles. Cambridge: Institute of Terrestrial Ecology.
Kerney, M P and Cameron, R A D (1979). A Field Guide to the Land Snails of Britain and North-West Europe. London, Collins.
Killeen, I J (1992). The Land and Freshwater Molluscs of Suffolk. Suffolk Naturalists' Society, Ipswich.
Seddon, M B (1996). Distribution of Vertigo moulinsiana (Dupuy, 1849) in Europe. In: Drake, C M (ed), Vertigo moulinsiana, Surveys and Studies Commissioned in 1995-96, pp 56-68.
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