Posted on Nov 13, 2015

23,000m of bank surveyed on Great Western Route Modernisation project.

Throughout March to September 2015, Thomson Ecology undertook water vole surveys on 61 water bodies within Sections 8 and 9 of the Great Western Route Modernisation (GWRM) project.

This amounts to a staggering total of 23,238 metres of bank side surveyed! Signs of the species have been identified in two areas on the route, both of which are close to previously recorded populations. The results of the surveys are being reported back to ABC Electrification, the design teams and Network Rail, and Thomson Ecology is then advising on appropriate avoidance or mitigation techniques that can be used to allow the electrification works to progress in a legal manner that will minimise any detrimental impacts on the water vole populations.

The water vole (Arvicola amphibious) is a semi-aquatic rodent superficially thought to resemble a rat, but, on closer inspection, it is quite different – with a rounder nose, deep brown fur, flatter chubby face and short fuzzy ears. Additionally, unlike rats, their tails, paws and ears are covered with hair.

Water voles tend to live along the banks of rivers, streams and ditches, around ponds and lakes, and in reed beds and areas of wet moorland. Their burrows can often be distinguished from the homes of other mammals by the presence of neatly nibbled ‘lawns’ at the entrance and piles of grass, and stems that have been nibbled at a distinctive 45o angle.

Formerly widespread in the UK they are now Britain’s fastest declining mammal species; their population has reduced by over 90% in the last 50 years. This rapid drop is due to a number of reasons including: pollution; habitat loss and fragmentation; and predation from American mink, a non-native species. Water voles are legally protected in Britain and conservationists are trying to help water vole populations re-establish through re-introduction programmes, mink control and habitat management of riverbanks.

Probably the best known water vole is Ratty, a leading character in the 1908 children’s book The Wind in the Willows by Kenneth Grahame, but the accompanying picture is of a water vole spotted by Thomson Ecology staff carrying out ecological surveys at Magor Marsh Nature reserve, close to the Great Western Mainline and Magor Road Bridge.

Water voles are most active during daytime hours, so not as elusive as some of our other British wildlife. Next time you are by a river keep an eye out for the signs of water voles and listen out for a distinctive ‘PLOP’ as they enter the water from the bank – you could be in for a treat!


  • Look up! Water voles can climb trees to find food.
  • Despite their name they are not always found near water. Recently a thriving population was found on rough grassland near a housing estate in Glasgow – nowhere near water!
  • They excavate their burrows with their large front teeth.
  • Water voles can have up to 5 litters in a year, producing up to 25 young.
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      Knowledge Hub 23,000m of bank surveyed on Great Western Route Mo...