Practical techniques: Water vole
England, Wales and Scotland
The water vole (Arvicola terrestris) is the largest species of vole in Britain and inhabits canals, rivers, streams, ditches and other wetland areas. They create burrows in the banks and feed primarily on reeds, rushes, sedges and other aquatic vegetation. Water voles swim, dive and climb well and can be found at quite high densities in good habitat. They are however declining in Britain primarily due to predation by the American mink (Mustela vison) and a general decline in habitat quality. Water voles do not hibernate but spend much of the winter below ground.
Protection and its implications
In April 2008, water voles received full protection under the Wildlife and Countryside Act 1981 (as amended). This makes it an offence to kill or injure water voles, and to damage, destroy or obstruct access to places of shelter or protection (i.e. burrow systems) and to disturb voles while they are using such a place. The water vole is listed under Section 41 of the NERC Act 2006 (England), Section 7 of the Environment Wales Act 2016 and Section 2 of the Nature Conservation (Scotland) Act 2004. It is therefore a priority species in England, Wales and Scotland. Government policy is that local planning authorities should consider such species when determining planning applications. Consideration of priority species would also be expected in the UK as part of the legal Biodiversity Duty.
If water voles are present on a development site, it could be a reason for the refusal of planning permission unless the applicant can clearly demonstrate that they will be protected during the development process and that disturbance is kept to a minimum. In some cases this may be extended to include management measures post-development to prevent negative impacts during the operational phase of a development. Sometimes it might be necessary to work within occupied water vole habitat, or there might be a need to destroy their burrows to allow development to occur. In order for this to occur legally, it would be necessary to remove the water voles before development works begin usually by either forced displacement or trapping and translocation. In England and Wales there is no specific licensing system to permit mitigation works such as this solely for the purpose of development. Instead mitigation works of this type should be undertaken under a conservation licence issued by the appropriate statutory agency. Licences of this type are granted to permit trapping and translocation with the objective of providing conservation gain. However, in Scotland there are specific licences for development affecting water voles.
Mitigation techniques
Protection of individual water voles
Water voles are generally restricted to ditches, watercourses and other wetland habitats and the immediate area of land around them. These features can often be retained within the development site. In this case, all that may be required to protect water voles would be to erect protective fencing around the water vole habitat and ensure that construction activities and storage of materials do not occur within this zone. When relatively small areas of habitat are affected by development which do not support water vole burrows and there are low numbers of water voles present in the surrounding area, it may be possible to displace water voles into adjacent areas without using traps. This is achieved by progressively removing the vegetation both on the banks and in the channel and gradually making the habitat unsuitable for water voles so that the water voles move away by themselves.
When larger areas of habitat are affected, or water voles fail to move on after the vegetation has been removed, it may be necessary to use a system of water vole fencing and traps in order to remove the voles from the development area. Where this approach is taken it is necessary to agree both the approach to trapping, and the receptor site that will be used under licence from the appropriate licensing agency. In England and Wales mitigation should aim to not only minimise the risk of an offence during development works, but promote the long term conservation of water voles. To achieve both objectives it is necessary to plan water vole translocations carefully and select receptor habitat that will be protected from degradation and free of mink for the foreseeable future.
In some cases, such as when new habitat needs time to become established before it is ready for release of water voles, or water voles are being captured at a time of year that is inappropriate for their release, it may be necessary to take water voles into captivity. As water voles are short-lived animals, it is usually the offspring of the captured animals that are released when the new habitat is ready. This also means that more animals can be released than were captured and this could improve the chances of water voles establishing themselves at the new site.
Maintaining habitats for water voles
Excluding water voles from part of their habitat, or translocating them to alternative habitat, is usually associated with enhancements to adjoining water vole habitat or creation of new ditches and backwaters to accommodate the displaced water voles. Whichever approach is adopted, the following measures may benefit water voles:
- Creating steep earth banks in which the water voles can burrow
- Reinstating meander bends, and ponding where watercourses have previously been straightened
- Ensuring water is present all year round
- Encouraging the dense growth of grasses and herbs on the banks and bank tops
- Creating shallow marginal areas with reeds, rushes and sedges growing in abundance at the base of both banks
- Creating refuge areas above winter flood levels
- Removing excessive tree and shrub growth along ditch and stream banks
Where erosion protection or bank stabilisation is required, the use of ‘soft engineering’ techniques including hazel hurdles and staked coir-fibre rolls may allow water voles to continue occupying their habitat.
Monitoring
The use of radio collars for water voles has recently been criticised – radio-collared females are more likely to give birth to male offspring, possibly because the collar causes them to become stressed. Alternative, less invasive methods of monitoring water voles are therefore recommended, including burrow, feeding signs and trapping surveys. Length of monitoring period will depend upon the nature of the mitigation. Populations can rapidly become extinct if mink move into the area, so mink monitoring should always be undertaken as part of ongoing habitat management.
Timing of works
Exclusion and trapping of water voles should only be undertaken in March and April and September and October when the water voles are active and are less likely to have dependent young in their burrows. If females with dependent young are caught, these should be released back into the development area for capture at a later date. Releases of water voles are best undertaken in spring and summer, with late autumn releases likely to be less successful.
Further reading
Natural England (2011) Water voles: guidance for planners and developers. Natural England, Peterborough.
Natural England (2011) TIN042 Water Voles and Development: Licensing Policy (3rd edition). Natural England, Peterborough.
Dean, M., Strachan, R., Gow, D., & Andrews, R. (2016). The Water Vole Mitigation Handbook (Mammal Society Mitigation Guidance Series). Eds. Fiona Mathews and Paul Chanin. The Mammal Society, London.
Natural England (2015) Water voles: surveys and mitigation for development projects. https://www.gov.uk/guidance/water-voles-protection-surveys-and-licences