water vole

Water Vole Survey Guide

Water Voles at Acer Ecology

At Acer Ecology, we undertake a range of ecology and protected species work and regularly carry out Water Vole Surveys. Read on to learn a little about water voles and water vole surveys in our water vole guide!

Population Decline

Water voles have a wide distribution across Europe where populations are generally stable. However, water voles are one of the UK’s most threatened mammals. Until recently, the water vole was widespread in the UK. However, water voles have disappeared from 90% of sites where they are previously known to have lived. The crash in numbers has been one of the fastest and most severe of any mammal species in Britain and it has happened mainly over the last twenty years.

Water Vole Feeding StationThe severe population decline is largely due to the rapidly expanding number of American mink (Neovision vision) decimating the water vole population. Mink was commonly farmed for fur during the 20th century and the inevitable escapees have adapted well to life in the UK. They are now well established, despite efforts to control them. They predate on a wide range of native wildlife, including water voles. Water vole populations have also suffered due to pollution of watercourses, agricultural intensification and habitat loss.

There are some good news stories: water voles are getting extra help from conservation groups such as The Gwent Wildlife Trust who are using ‘mink rafts’ within nature reserves such as Magor Marsh.  Mink rafts are a means of both detecting and trapping the invasive mink in an attempt to control the numbers. There are also ambitious projects such as The Gwent Levels Water Vole Project which was set up to reintroduce water voles to the Gwent Levels after they disappeared entirely from the Levels in the early 2000s.

Legislation and Protection

In light of severe population declines, water voles are protected under Schedule 5 of the Wildlife and Countryside Act (1981). They are given so-called ‘partial protection’, which prohibits the deliberate killing or injury of individuals, damaging, destroying or blocking access to their places of protection (either intentionally or through ignorance), disturbing them in a place of shelter, or possessing them. Water voles are listed as a priority species in Wales Under Section 7 of the Environment (Wales) Act 2016 and under the Natural Environment and Rural Communities (NERC) Act 2006 as being of principal importance for maintaining and enhancing biodiversity in England. Only licensed ecologists are permitted to handle the water voles. The habitats of common water voles are not specifically protected.

If development is likely to affect potential water vole habitat, a survey will be required in order to confirm their presence or likely absence from the site. If water voles are present and their habitat or the animals themselves will be affected by the development, a conservation licence will be required from the statutory agency (Natural Resources Wales or Natural England). In cases where the loss of water vole habitat is unavoidable, mitigation may include the ‘exclusion’ of the animals from the development area, in addition to habitat creation and restoration. A preferred method is always to modify the scheme so that any habitat damage or disturbance to individuals can be avoided and water vole habitat can be maintained.

Water Vole Surveys

Water vole surveys are carried out during the breeding season which lasts from March to September. This is the time when water voles are most active. The optimal time to survey is in May and June during the peak breeding season and before the vegetation has grown. Surveys must not be carried out immediately after periods of heavy rain as field signs are likely to have been washed away.

Useful Water Vole Survey Equipment:

  • Warm, waterproof clothing
  • Sturdy footwear (wellingtons or walking boots)
  • Fully charged mobile phone – for safety reasons
  • Packed lunch with plenty to drink
  • Camera
  • Binoculars – useful for checking signs on the opposite bank or places that are difficult to access
  • Walking pole or stout stick- for checking water depth and looking through dense vegetation
  • Backpack
  • Ziplock bags to collect and keep field signs
  • Antibacterial hand wipes or hand sanitizing gel
  • Hat or cap to keep off the sun
  • Sun cream and insect repellent

Distribution and Habitats

Water voles are a widespread species across Europe and beyond. They have a wide distribution across the UK but are absent from Ireland and some of the Scottish islands. Preferred habitats include freshwater marshes, wetlands and slow flowing river banks. They can be found in both the uplands and lowlands, usually favouring well vegetated, steep banks. They require earth in which to dig burrows so are very unlikely to be found in rivers which have been channelled with concrete or culverted. Water voles will rarely be encountered far from the water, except in some parts of Scotland where they live underground in grasslands and are not aquatic.

Field Signs

There are several common field signs to look out for, some of which can be conspicuous once you know what to look out for:

Burrows and Lawns – Burrows usually consist of holes along the water’s edge and in the bank above. They are usually slightly wider than high with a diameter of 4-8cm. Sometimes the entrance of a burrow will feature a neat ‘lawn’ where the water vole has kept the vegetation very short.

Feeding Signs – Water voles will leave neat piles of chewed lengths of vegetation approximately 10cm long. They eat a huge variety of plant species, including but not limited to grasses, reeds and sedges. Water voles chew off the vegetation at a distinctive 45-degree angle. Only green vegetation should be used as a sign of recent water vole presence as old vegetation does not necessarily mean water voles are still present. Equally, an absence of feeding signs does not confirm the absence of water voles from a site.

Pathways – Water voles often create pathways in vegetation. These form low runs or tunnels 5-10cm wide pushed through the vegetation. They can usually be found close to, around or leading to the water’s edge and linking to burrow entrances or favoured feeding areas. There are often muddy patches where water voles enter and leave the water.

Latrines – Water voles sometimes use their excrement to mark and protect their territory. Droppings are usually 8-12mm long, cylindrical with blunt ends, green/brown/black and have no odour. They are slightly bigger than tic tac size and similar in shape. Often the accumulations of droppings become wet and mushy in the rain and can be good places to spot footprints.

Footprints – ‘Star’ shaped with the rear digits splayed out to almost 90o. The hind feet have five digital pads whereas rats have six. Hind feet prints are approximately 3cm x 3cm.

Plopping Sound – It is important to be quiet as possible during a water vole survey. This gives you a better chance of hearing the characteristic ‘plop’ sound a water vole often makes when entering the water. The sound is similar to that of a rock being dropped from a height into a pool of water. Being quiet will also avoid disturbing the voles and scaring away wildlife.

Differences with Other Similar Species

If you’re lucky you might actually see a water vole during your survey. However, be sure not to confuse water voles with similar looking animals, some of which are also likely to be swimming.

Field (Microtus agrestis) and Bank (Myodes glareolus) Voles – Water voles (up to 22cm, head to body length) are much larger than field and bank voles (up to 11-12 cm, head to body length) which are found in grassland habitats (field vole), woodland and scrub (bank vole). Field signs of bank and field voles are similar to those of water voles. Owing to their smaller size, field and bank vole signs are also smaller. Field vole droppings are usually smaller than a grain of rice.

Mice – Mice are significantly smaller than water voles. Mice often hop as well as running whereas voles do the opposite. Voles, in general, have proportionally smaller ears, eyes and tails than mice.

Rats (Rattus norvegicus) – Found in a range of habitats and often along watercourses, rats are good swimmers. Rats have more prominent ears, larger eyes and a more pointed snout than water voles. They have a longer, hairless tail, whereas a water voles tail is relatively short and furry.

American Mink – Grows up to 47cm (head to body), usually very dark looking with a small white chin spot and thick looking fur. Like water voles, they swim with much of their body out of the water.

Otter (Lutra lutra) – Growing up to 90cm long, otters are significantly larger than water voles and mink. Otters usually swim with mainly just the head visible. Voles tend to appear buoyant when swimming with much of their body out of the water.

What Can Acer Ecology Offer?

Acer Ecology has extensive experience in surveying and designing mitigation for water voles and can advise you on survey methodology, legal protection, mitigation options and the timing of development works. We also carry out Bat Surveys, Preliminary Ecological Appraisals, Bird Surveys, Great Crested Newt Surveys and a range of other ecological work.

For more information about Water Voles Surveys, call us on 029 2065 0331, contact us on info@acerecology.co.uk or take a look at the People’s Trust for Endangered Species video guide to water voles.