Once common on all of Durham's rivers the water vole has suffered a catastrophic decline in numbers and distribution in County Durham, as it has throughout most of the UK. Today the water vole is restricted to a few small colonies in County Durham mostly in our urban areas or in places not yet reached by the American Mink.

Water vole numbers have been dropping since 1900, but in the last 20 years the decline has accelerated alarmingly. National surveys have shown that water voles have been lost from more than 89% of sites that they inhabited sixty years ago, this makes them the fastest declining mammal in the UK. Predictions for the water voles future are bleak, based on current population declines it is possible that the water vole may become extinct in the UK by 2016.

Their disappearance appears to be a classic case of habitat loss and then fragmentation. This leaves small isolated populations that are vulnerable to other threats such as flooding and pollution incidents. The water vole is easy prey for the American Mink, which has spread throughout the country, the arrival of this new predator able to hunt the voles both in the water and in their burrows has lead to the systematic eradication of many of these small water vole populations.

Typical water vole habitat includes slow-flowing watercourses with tall, luxuriant bankside vegetation. Water voles favour grasses and sedges as a food source and will eat the bark of certain trees such as willow during the winter. Water voles also need steep sided earth banks where they can excavate their burrow systems.

The water vole is listed in the UK Action Plan on Biodiversity, published by the Government in 1994. The BAP sets out strategies and targets for conserving species and habitats for the next twenty years. Durham Wildlife Trust has undertaken a water vole survey of North Durham and South Tyne and Wear as well as managing its nature reserves for the benefit of water vole populations.