Water Vole Survey
Where water courses, ditches, ponds, lakes, wetland habitats and associated riparian vegetation are deemed likely to be affected by project proposals, a water vole survey may be required, which aims to establish the presence/ likely absence, and distribution of water vole territories on site.
Water voles are found along the banks of rivers, streams, ditches, ponds, lakes and a variety of wetland habitats throughout much of Britain, though they are absent in parts of south-west England and Wales, northern England and Scotland, and scarce throughout upland areas. The British population has endured a long term decline, disappearing from 94% of their former sites, primarily due to a combination of habitat loss and degradation, and the introduction of the predatory American mink. They are protected under UK law, making it an offence of kill, capture, or disturb them, though their habitat is not specifically protected. Works affecting water voles are subject to licensing procedures.
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The appraisal is used to inform the emerging scheme design, enabling significant ecological effects within the zone of influence to be avoided, mitigated, or compensated for, where necessary. This ensures the continued favourable conservation status of water voles, post development, and ultimately compliance with nature conservation legislation and planning policy.
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There are two types of water vole survey, comprising Habitat Suitability Assessments (HSAs) and presence/ likely absence surveys. HSAs involve assessing the likelihood of water vole presence within habitats, generally based on eight indices: vegetation composition (species diversity); vegetation structure; and ecological connectivity to the wider landscape. A habitat score is derived from the combined totals, with higher scores equating to more optimal suitability. If the assessment indicates that the features are unsuitable or population sinks, they can be scoped out of the study. However, sub-optimal or optimal scores may necessitate further targeted survey.
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Presence/ likely absence surveys involve systematically traversing a section of watercourse, margins of a water body, or area of wetland, searching for evidence of water vole activity, and attempting to interpret the population size and distribution, where present. The survey typically encompasses a 2m buffer of riparian habitat, either side of the water feature, and extends 100m along suitable habitat beyond the site. The field survey is typically supplemented by a desk study, utilising maps and aerial photographs of the surrounding area to identify ecological connectivity, and published records of water voles, purchased from the local records centre.
Requirements for any necessary avoidance, mitigation, or compensation measures will be identified, and opportunities for ecological enhancement will be outlined, to integrate on-site biodiversity net gain into the scheme at an early stage, where possible.​ If the proposals are deemed likely to adversely affect water voles, a mitigation licence may be required, prior to the commencement of works.
Certain water vole surveys are seasonally constrained, making it prudent to plan ahead and consider ecological issues early on in the planning process. A robust water vole survey at an early stage in project planning and design can therefore deliver significant benefits, avoiding potentially costly and time-consuming delays.​
When
HSAs can be undertaken throughout the year. Water vole presence/ likely absence surveys must be undertaken between April-mid October inclusive.
Why Us
With over fifteen years' experience in undertaking ecological surveys, mitigation design, licensing, site supervision, and monitoring, our team of expert ecologists can help guide your project through the planning process.
Our licensed ecologists can appraise your site's water vole suitability, undertake surveys, design mitigation strategies, and apply for mitigation licences.
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By working closely with our clients, we ensure that their developments progress smoothly and in full compliance with the law, orchestrating the best possible outcome for them and the natural world.
