Arvicola terrestris

Range & Status

Widespread across the northern Palaearctic from Great Britain, northern Spain and Scandinavia to Siberia (Harris & Yalden, 2008) and absent from Ireland. The complex detail of present Water Vole distribution in Great Britain, which includes a good number of island populations, is given in Harris and Yalden (2008). Britain' s fastest declining mammal, it has suffered a recent decline of almost 90%. An estimated summer population of 875,000 is given by Macdonald and Tattersall (2001). Water Voles have not only disappeared from whole catchments but entire counties, including Cornwall.

Regional Distribution

There are very few historical Water Vole records for Cornwall but these, however, show that they were widespread throughout the county. It is believed that the Water Vole is now extinct in Cornwall. The last two confirmed records were in 1998, from near Par (SX05) and Godolphin (SW63) (Jefferies, 2003). Every year, sightings of Water Vole are reported to the Cornwall Wildlife Trust, but when followed up these have proved to be negative, or at least no field signs could be detected to confirm the records.

Habitat & Ecology

Usually found in lowland areas on the vegetated banks of rivers, streams, dykes and ditches, favouring slow-moving water (Corbet & Harris, 1996), usually within two metres of the water' s edge where water is present throughout the year (Harris & Yalden, 2008). Reed-beds and ponds are also important habitats and provided many of the last refuges for Water Vole in Cornwall. Water Vole is predominantly vegetarian, and particularly keen on the Common Reed Phragmites australis , sedges, grasses and other vegetation (Corbet & Harris, 1996). Very occasionally, female Water Vole eat insects, molluscs and fish (Jefferies, 2003).

Threats

A number of factors have contributed to the dramatic decline of the Water Vole in Britain, but the loss of Water Vole in Cornwall (and elsewhere) can be attributed to habitat loss and predation by American Mink Mustela vison . The impact of this decline is greater due to these, and other, factors acting together. The first British Water Vole survey 1989-1990 (Strachan & Jefferies, 1993) identified the South West as a stronghold for American Mink and habitat loss includes development of wetlands, engineering of watercourses (e.g. for mining) and recent agricultural practices (notably ploughing and grazing close to the water' s edge). Suitable habitat with a good cover of vegetation is important for Water Vole; it provides food, and helps evade predation, including attacks from avian predators.

Conservation

It is believed that the decline of Water Vole nationally has been halted due to habitat restoration and American Mink control programmes. With its strong reproductive potential, however, it should be possible to increase numbers and populations of Water Vole, in conjunction with habitat management, translocation and re-introduction, all important tools to achieve this. A partnership project to reintroduce Water Vole to Cornwall is being developed by the CWT, the Environment Agency (EA), South West Water (SWW), Natural England (NE) and the Royal Society for the Protection of Birds (RSPB) (Stokes, 2008). From 6 April 2008 Water Vole received an increased level of protection under the Wildlife and Countryside Act 1981 (Variation of Schedule 5) (England) Order 2008. Water Vole is now fully covered by the provisions of this increased protection and adds prohibitions against intentional killing, taking or injury, possession and sale. Listed (short list, with action plan) as a globally threatened/declining species (BSGR, 1995) and included in the Biodiversity Action Plan list for Cornwall.