Water vole  (Arvicola terrestris)

The shocking decline in both range and numbers of the water vole is due to a number of factors. The large-scale loss and fragmentation of sensitive waterside habitats due to riverbank modification, drainage and flood defence works has been an important factor (5), as has the pollution of waterways and poisoning by rodenticides (3). Perhaps the most serious threat facing the beleaguered water vole is predation by the introduced American mink (3). When threatened, water voles often dive under water and kick up a cloud of mud to hide from predators. This does not fool the American mink, however, which is able to successfully hunt the water vole on land, in the water and even inside the burrow system. There is a correlation between the loss of water vole sites and American mink presence (5), and the introduced mink has even resulted in local water vole extinctions (2).

It is likely that the water vole will become extremely rare in areas colonised by American mink; the elimination of American mink is unrealistic, but numbers can be controlled in key areas in an attempt to ease the pressure on the water vole. Habitat enhancement such as the encouragement of a broad variety of waterside vegetation and recreation of natural features such as water meadows and oxbow lakes could benefit the species. Under the Wildlife and Countryside Act 1981, it is an offence to disturb, obstruct or damage water vole burrows. A booklet has been produced by English Nature, providing guidance on the water vole for planners and developers (8). Research into the ecology and habitat needs of this species is essential, as little work has been carried out on it due to its previously common status (3).