Water voles

When developing or altering a site on or near waterways, it is important to consider if water voles are present, as they are protected by legislation and planning policy. To determine the likely impact of a development on local water vole populations, water vole surveys may be required, and appropriate mitigation measures may need to be implemented to reduce any adverse impacts to water voles and their habitat.

Water voles: ecology

Water vole eating grass © Laurence Arnold / Flickr.com
Water vole eating grass © Laurence Arnold / Flickr.com

Water voles live in colonies along water courses throughout the UK. They are protected under the Wildlife and Countryside Act 1981 (as amended) and are also a UK priority conservation species. Water voles are rarely seen in winter but do not hibernate. They overwinter in burrows maintaining energy levels by sleeping and feeding on stores of tubers, bulbs and rhizomes.

Water voles sometimes plug burrows with mud and vegetation during winter to maintain heat. Between March and October, breeding females mark their territory using discrete latrine sites. Water voles used to frequent most water ways in England, Scotland and Wales, but it is thought they have been lost in up to 90% of these sites. The decline is largely attributed to habitat loss and predation by the invasive American mink.

Will water voles and their habitat impact on my development plans?

Water vole in a river drainpipe, New Chapel, Surrey © Peter Trimming Flickr.com
Water vole in a river drainpipe, New Chapel, Surrey © Peter Trimming Flickr.com

Water voles are fully protected under Section 9 of the Wildlife and Countryside Act 1981 (as amended) and are also UK priority conservation species. It is therefore an offence to intentionally kill water voles, damage or obstruct access to water vole burrows or disturb them in a place of shelter. For this reason, any work or development that could disturb water voles or their habitat should be preceded by a survey to determine the presence or likely absence of water voles within the site.

Water voles: surveys

Thomson ecologist carrying out water vole survey in a canoe © Heather Clayson / Thomsonec.com
Thomson ecologist carrying out water vole survey in a canoe © Heather Clayson / Thomsonec.com

The optimal period for undertaking water vole surveys is from April to October. This is when their signs are easiest to detect, for example, feeding remains, burrows, runs, footprints, latrines and droppings. On some sites, between June and September, surveys are less effective due to vegetation obscuring water vole burrows and signs used to confirm their presence.

To overcome this limitation, Thomson has employed a new survey technique which involves carrying out water vole surveys from a kayak. This allows more of the water bank to be surveyed and a more accurate record to be made of how water voles are using the water way. This approach may also be employed in areas which are not safe to access due to steep banks. The number of latrines recorded during survey visits provides an indication of the relative population size, which is often useful for determining appropriate levels of mitigation.

Licensing requirements for water voles

It is essential that all potential water vole habitat is assessed prior to proceeding with works. Ideally, the development design will be modified to avoid impacts on water vole habitat. However, if this is not possible and water voles are likely to be affected by the development, works will need to proceed under a licence from Natural England.

For projects where a small portion of the habitat is being affected (usually less than 50m) it may be possible to proceed under a displacement licence. Alternatively, for projects with a more significant impact, a conservation licence may be required. In both circumstances, mitigation and compensation measures must provide a net conservation gain for water voles.

Water voles: mitigation

Water voles burrow marking in a canoe as part of translocation © Heather Clayson / Thomsonec.com
Water voles burrow marking in a canoe as part of translocation © Heather Clayson / Thomsonec.com

Mitigation may include making habitat unsuitable to encourage water voles to disperse into adjoining suitable habitat, before development work starts. Alternatively, if large areas of habitat are being affected, a translocation may be required, which involves capturing and moving water voles to a suitable receptor site. These activities may only be undertaken if they are carried out under a licence granted by Natural England.
Compensation measures can be used to offset any remaining negative impacts for water voles that cannot be mitigated otherwise. These can include

  • Providing more or better habitat for water voles to make up for any loss through development
  • Improving water quality
  • Enhancing bank structure and vegetation
  • Controlling mink as part of mitigation, compensation and licensed action when dealing with water voles (as advised by Natural England).

How we can help

If your development site is near and or on a waterway and you think your works will affect water voles, or you are unsure and need a professional opinion, Thomson can support you. You may require a preliminary ecological appraisal, which could lead to survey and possibly mitigation work – all services Thomson can provide. Or it may show that your works are unlikely to affect water voles. Get in touch with us today to see how we can help.

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