Water Vole Surveys

Background

Water voles (Arvicola amphibius) burrow into the banks of slow moving water bodies, such as ditches, dykes, streams, slow flowing rivers and large ponds. Water voles were previously common throughout mainland Britain; however due to the loss of habitat and predation by the American mink (Neovision vision) , their numbers have suffered dramatic declines, by up to 90% in some places.

The water vole receives legal protection under the Wildlife and Countryside Act 1981 (as amended). This legislation protects against deliberate killing or injuring and sale, as well as intentional damage, destruction or obstruction of the access to any structure or place which water voles use for shelter or protection or disturbance to water voles while they are using such a place. It is therefore important that any works directly affecting or within close proximity to suitable water bodies are preceded by a water vole survey to determine presence or presumed absence of this species and any specific mitigation that will be required by the Local Planning Authority.

Timing

The water vole breeding season runs from April to September. This is the ideal time to carry out a water vole survey as the water voles will be highly active and leave many signs, such as latrines (conspicuous piles of droppings) which can be used to confirm their presence during a survey. Habitat assessments can be undertaken over winter and surveys at that time can determine presence; although absence of water voles can only be confirmed by spring or summer surveys. To confirm presumed absence, two survey visits with be conducted, the first conducted between mid-April and June and the second between July and September. If water vole presence is confirmed during the first visit, it may not be necessary to undertake the second visit. Water vole surveys are often combined with otter surveys.

Methodology

Habitat Assessment

As part of every water vole survey, the habitat suitability for this species will be assessed. This will include an assessment of the foraging resources, the suitability of the banks for burrowing and the presence of adequate cover / shelter.

Surveying for Water Vole Evidence

The water vole surveys will follow the methodology stated within the Mammal Society’s Water Vole Conservation Handbook, 3rd Edition (Strachan et al., 20167), and The Water Vole Mitigation Guidelines (Dean et al., 20168). The survey involves searching for the following evidence of water vole:

• Water vole burrow entrances;
• Water vole latrines or droppings and otter spraint;
• Feeding stations and feeding remains;
• Footprints in soil and mud;
• Waterside runs and pathways through vegetation;
• Sounds of water vole entering the water (a distinctive ‘plopping’ noise).
• Floating rafts may be deployed along the watercourse if a thorough search of the banks is not possible. Water voles will use the rafts as feeding platforms and will deposit droppings on them

Following the Survey

Water Vole Mitigation

Where water voles are found, the most common recommendation is to ensure all site works remain a suitable distance from the banks of the waterbody, in order to avoid disturbance / harm to this species. However, when works within the waterbody or close to the banks cannot be avoided, a number of mitigation options are available.

Displacement

Water voles require adequate cover and foraging resources within their territory. If these are removed, the habitat becomes unsuitable and water voles will move of their own accord. If a small section of a waterbody (generally less that 100 m) is to be directly affected, the water voles can be encouraged to move to a different area of the waterbody by strimming the vegetation and then maintaining it at a low height. This is most effective when undertaken during late February to early-April; however this method is only suitable for very short sections of affected habitat. This action must be carried out in accordance with an ecologist that holds the relevant class licence from Natural England.

Translocation

When a whole waterbody or significant stretch of bankside habitat will be affected by development, or a large population of water voles is identified during the initial survey work, the removal of the water voles from the area of works by translocation may be necessary. A suitable receptor site would be required, which would be identified by further survey work and habitat assessments. Once a receptor site has been identified, a trapping scheme within the area to be affected would be implemented. This would involve the daily monitoring of the traps, removal of any water voles caught and the release of the water voles into the receptor site. Post-release monitoring would also normally be required. Translocations can only be carried out under a conservation licence from Natural England.

EMEC Land Management are able to carry out mitigation works with regards to water voles, as well as habitat enhancement measures.