A water vole munching on water plants in a stream at Barnes WWT
The European Water Vole (Arvicola amphibius formerly called A. terrestris) is a semi-aquatic mammal that resembles a rat. In fact, the water vole is often informally called the water rat.3 Some authorities consider the Southwestern Water Vole in the same species, but it is now generally considered a distinct species.24 Water voles have rounder noses than rats, deep brown fur, chubby faces and short fuzzy ears; unlike the rat their tails, paws and ears are covered with hair.
Water voles reach 140–220mm in length (5–9 inches) plus a tail of 55%–70% of this. Adults weigh from 160–350 g (6–12 ounces), juveniles weigh less but must reach around 140–170 g (5–6 ounces) to be able to survive their first winter.
In the wild, they survive for 2 years on average; most do not survive a second winter. In captivity, they normally start to deteriorate in condition as they approach their third year becoming thinner and losing much of their fur, nearly all die during their third winter.
The water vole population in the UK has fallen from its estimated pre-1960 level of around 8 million to 2.3 million in 1990 and to 354,000 (other source: 750,000) in 1998. This represents a 90-95% loss. It is still declining dramatically, the most recent estimate for 2004 is around 220,000. This decline is partly attributed to the American Mink, an aggressive predator of the vole, together with unsympathetic farming and watercourse management which destroyed parts of the water vole’s habitat.
On 26 February 2008 the UK Government announced full legal protection for Water Voles would be introduced from 6 April 2008.11
Consequently, the water vole is the UK’s fastest declining mammal and efforts are under way to protect the water vole and its habitat from further destruction. One aspect of water vole conservation in the UK is focussed on non-linear habitats such as reed bed which support extensive networks or metapopulations. Other areas supporting healthy populations of water voles are large conurbations such as Birmingham and London and some upland areas where American Mink are scarce. Across the UK the Wildlife Trusts and other organisations are undertaking many practical projects to conserve and restore water vole populations.