Water voles

They were once common throughout Britain, and in the past the waterways of Derbyshire were dotted with colonies of this enchanting creature. Sadly, this is no longer the case, and the sight of a water vole is now increasingly rare. The collapse in water vole numbers, first discovered in the 1990s, has led to the water vole’s listing as one of Britain’s most critically endangered mammals with the highest level of legal protection.

The water vole (Arvicola amphibius) is diurnal and was once easy to see. Older people cherish memories of Ratty, sitting by the stream munching, swimming across the river or vanishing with a loud plop. In recent years, population decline and a decrease in people’s familiarity with the countryside have led to the water vole becoming a totally unknown species. To many, a large rodent that clearly isn’t a mouse must be a rat. This confusion over identity has been the cause of harm to these harmless animals. But what is a water vole?

The water vole is a medium-sized rodent native to Britain and is by far the largest of the British voles. It has a rounded body and face with chubby cheeks and a blunt nose. Its ears are small, covered with fur, sit close to the head and are almost invisible while the eyes are small, dark, prominent and extremely beady in appearance.

The average length of the head and body of an adult male water vole is around 225 mm and its tail between half and two thirds that length again. Females are slightly smaller with head and body measuring around 220 mm plus tail. Males’ weight ranges between 246 and 386g and females’ from 225g to 310g. Scottish water voles tend to be slightly smaller and lighter.

The water vole’s fur is a rich brown or chestnut colour across the back and sides with a paler brownish white underneath. The adult has long, gleaming guard hairs that give it a shaggy appearance, with an undercoat of finer hair that traps air and provides a degree of thermal insulation. While being an efficient swimmer, unlike the otter, the water vole is not an amphibious mammal and cannot stay long in or under water.

Water voles live along water courses such as streams, rivers, drainage channels, also small lakes, marshes or ponds. Ideal habitat has wide margins of waterside (or riparian) vegetation that provides both a varied food source and a measure of protection from predators. They live in bank side burrows which are often quite extensive, with interconnecting tunnels, nesting chambers, food storage areas and several entrances above and below the water line.

Water voles are mainly herbivorous, and feed on large quantities of plant material. They consume around 80% of their body weight daily with lactating females eating much more. Their main diet consists of the stems and leaves of waterside plants, grasses, sedges and other herbaceous plants.

The water vole breeding season in England begins in April and ends in September. Breeding females produce between one and five litters a year, with three being an average number and five or six young in each litter.

Few water voles survive two winters, and survival over three winters is very rare in the wild, but some water voles in captivity have lived to this age.

Habitat loss together with climate change, agricultural intensification and ever increasing pressure of leisure pursuits in our crowded island have made the habitable world of the water vole ever smaller and more threatened. But it is the spread of the predatory American mink throughout the river systems of Britain that has principally caused devastation to water vole populations.

The good news is that by research and conservation effort we know just how to save the water vole. Here at Haddon we are maximising the opportunities for water voles to flourish by restoring waterside habitat along many stretches of the rivers Wye, Derwent, Lathkil and Bradford and by taking other measures to help them. But we can all be careful not to disturb wildlife along the river banks and by keeping dogs out of the water and under control.

Let’s hope that future generations can watch this enchanting animal, that somehow epitomises the gentle, intimate and quiet life lived by wild creatures along our Derbyshire rivers.

Christine Gregory