Species Biodiversity Action Plans (Summaries)

Species Biodiversity Action Plan -
Water vole

species_water_vole.jpg (8228 bytes)

Common name: Water vole
Scientific name: Arvicola terrestris

Description

The water vole is Britains largest vole with an adult weight of between 200 and 350g.

It is an excellent swimmer, and in Britain is generally found near to flowing or still waters, although it has a preference for slow flowing watercourses with stable water levels. They are herbivores, and generally feed on lush bank-side vegetation (rushes, reeds and sedges) although in winter roots and bark supplement the diet. Water voles excavate extensive burrow systems, often with many entrances, some under water for protection, and consequently steep earth banked watercourses are the preferred habitat.

Water voles are often mistaken for brown rats, although rats have pointed faces and greyish brown fur where as water voles are chocolate brown in colour with a pinky-orange belly and flanks, and are more blunted in shape.

Legal Protection

  • Under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended) it is an offence to damage, destroy or obstruct access to, any structure or place used by water voles for shelter or protection (generally the burrow); or to disturb the voles while they using that structure or place.

Current Status

Although found throughout Britain, water voles are most prevalent in lowland areas close to water. They were once common and widespread, but in recent years the species has suffered a marked decline in both numbers and distribution, with a 1989-90 failing to record animals at 67% of sites previously occupied and predicting that this would rise to 94% by the year 2000.

Threats and Issues

  • Loss and fragmentation of habitats - particularly through inappropriate management and agricultural intensification (e.g. re-profiling, heavy grazing, drainage, vegetation control and extensive bankside tree-planting).
  • Disturbance of riparian habitats.
  • Predation - particularly by mink.
  • Pollution of watercourses and poisoning by rodenticides.
  • Persecution - sometimes in the mistaken belief that they are rats.
  • Severe winters and droughts - these lead to significant water level fluctuations.

Objectives (as pertinent to agriculture)

The national species action plan specifies two objectives:

  • to maintain the current distribution and abundance of water voles in the UK, and
  • to ensure that water voles are present throughout their 1970s range by the year 2010, considering habitat management and possible translocation of populations to areas from where they have been lost.

Conservation Advice

The following summarises a range of techniques thought to be beneficial in light of current knowledge.

1) Habitat protection

  • Fencing river banks - excessive grazing by livestock reduces access to suitable food and cover; and poaching of the banks compacts the soil and damages burrows. Therefore, at least some of the bank should be fenced off to provide refuges for water voles.
  • Mowing - if bank mowing is required, areas of uncut vegetation should be left at close intervals; this can be done on opposite banks, or by leaving one bank uncut. The cutting regime can then be altered annually.
  • Weedcutting - when weedcutting is required, marginal vegetation should be retained along one or both banks in 50m strips, or opposite banks should be cut in alternate years.
  • Dredging - should be carried out from one bank only, and if possible stands and/or marginal fringes of vegetation should be left to provide habitat, particularly where no other refuges are available. it may be suitable to leave shelving along banks during clearing operations in order to encourage the re-growth of fringe vegetation.
  • Bank reprofiling - if necessary, the bank profile should maximise the width of marginal vegetation, that can re-establish itself, and the bank could be stepped or with a steeper incline on the upper bank to facilitate borrowing. Work should as far as possible be restricted to small sections of watercourse, and nearby waterways or lateral channels should be left undisturbed to act as refuges.
  • Bank reinforcement - where reinforcement is required to prevent erosion, small scale repairs (using living willow withies, coir fibre bundles or other natural materials that will allow the bank to be used by water voles) should be encouraged.
  • Small channels - particular care should be taken when working on small channels, since these are of particular importance to water voles.

2) Water level management

  • Water level variability is detrimental to water voles since it inundates burrows or exposes tunnel entrances (allowing predation). Therefore, although sluices and weirs to regulate water level is often considered to be environmentally degrading (since it reduces natural variation), it can be beneficial for water voles.

3) Habitat enhancement

  • Habitat can be enhanced by the creation of suitable banks (see above), and vegetation. A list of suitable species for planting can be found in 'Water Voles' by Rob Strachan (see references).
  • A network of backwaters, ponds, floodplain ditches etc, should be reinstated (or perhaps created) where possible. Where this is to be done the overall length of suitable waterway should not be less than 500m, and should preferably be in excess of 1000m.

4) Agri-environmental schemes

  • Funding to assist in the creation of suitable habitats may be obtained under a number of agri-environmental schemes (e.g. Countryside Stewardship), for more details see the EMA Advisory System.

5) Rodenticides

  • The use of rodenticides should be discouraged, where other forms of control can be used and water voles are at risk.

6) Predators

  • Although it is impractical to erradicate American mink, it may in some cases be neccessary to control numbers, particularly in priority areas. The removal of female mink by live trapping in the months of February, March and April is recommended. Advice should be sought from the Environment Agency.

References and Further Information

Betts, C.J. (1998). Checklist of Protected British Species. Christopher Betts Environmental Biology, Worcester, UK.

British Agrochemicals Association. (1997). Arable Wildlife: Protecting Non-target Species. The British Agrochemicals Association, Peterborough, UK.

Flowerdew, J.R. (1997). Mammal Biodiversity in Agricultural Habitats. In: Biodiversity and Conservation in Agriculture: Proceedings of a Symposium held at The Stakis Brighton Metropole Hotel 17 November 1997, (Ed. Kirkwood, R.C.), pp. 25-40. British Crop Protection Council, Farnham, UK.

The Mammal Society. (1997). Fact Sheet No. 12: The Water Vole Arvicola terrestris. The Mammal Society, London.

Strachan, R. (1997). Water Voles. Whittet Books Ltd., London.

UK Steering Group. (1995). Biodiversity: The UK Steering Group Report, Volume 2: Action Plans. HMSO, London.

Woodroffe, G. (1996). The Water Vole. Mammal Society, London.

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