The Water Vole, Arvicola terrestris, is the largest of the British voles, being about the same size as the Brown Rat, Rattus norvegicus, with which it is often confused. This is hardly surprising because, in The Wind in the Willows, Kenneth Grahame’s ‘Ratty’, the most famous Water Vole of all, was called a ‘water rat’, a name still used by many country dwellers.