Water Vole nature conservation 'Walter Vole' drawn by Patron and Gruffalo illustrator, Axel Sheffler, for our project.

Only a few decades ago the Hogsmill River was teaming with water voles. Local residents could stand on a bridge and hear the characteristic ‘plop’ sound of a startled vole lunging from the bank into the relative safety of the river. Made famous by the character ‘Ratty’ in Wind in the Willows, the once common water vole has suffered the most catastrophic decline of any British mammal in the past century, both in population numbers and in distribution. Between 1989 and 1998 alone the population fell by almost 90%. These charismatic mammals are in fact easily distinguishable from a rat, with their rounder noses, glossy brown or black fur, short furry ears, furry tail and small black eyes. The water vole forms a key part of river ecosystems with their burrowing and feeding habits helping to create conditions where other wildlife and plants can thrive. 

The water vole’s decline has been driven by loss of habitat, pollution of waterways, increased urbanisation and rampant populations of the invasive American mink. Originally farmed in the UK for their fur, American mink were released into the wild and have proved a voracious predator of our native water vole. On the Hogsmill there have been no verified records of water vole in almost two decades and the plight of the water vole nationally has become a critically urgent wildlife conservation concern. 

Water vole reintroduction plan for the Hogsmill

Water Vole Nature Conservation HogsmillHowever, there is hope for the future in the form of reintroductions being carried out across the country. Leading the way is conservationist Derek Gow who breeds water voles at his farm in Devon. He works with groups across the country advising on and carrying out very successful water vole releases. Derek visited the Hogsmill to discuss the feasibility of future reintroductions and advised that the nature reserve could easily support a water vole population. Further up the catchment is Raeburn Open Space Nature Reserve in Berrylands and Elmbridge Meadows which have the potential to be suitable sites provided work is done to create grassier, more open habitat and increase light levels reaching the river. At Raeburn Open Space substantial works have subsequently been completed to improve the stream habitat, removing over 250 tonnes of concrete, reconstructing the bankside and improving and planting up both in stream and marginal habitats.

American mink have been sighted in multiple locations along the river and Derek advised that a strategically implemented eradication programme could be effective due to the relative isolation of the catchment. It was thought 16 mink rafts together with a team of water vole volunteers to monitor them would work well.

Additional benefits to water vole reintroduction

Water Vole Nature Conservation HogsmillRestoring a healthy water vole population to the Hogsmill would be a great achievement, bringing back a much loved mammal to a site where it had once thrived and reversing a decline caused entirely by human activities. In addition the works done to restore the water vole, together with the vole’s activities on the site, would improve the river habitat to a condition where it could support a wealth of other biodiversity. To achieve this aspiration the Trust will need to form a working group of organisations, local government and local residents to work together to achieve this goal.

If you or your organisation are interested in getting involved, contact our Nature Conservation Manager, Karolina Peret.