Fact Sheets

Water Voles

1. INTRODUCTION

Over the last 15 years the water vole has undergone one of the most catastrophic declines of a species ever witnessed in the U.K. Although they exist elsewhere in Europe, it is only in the UK where water voles are actually dependent on living by water. We therefore play host to a unique population. As a result of these factors, it is now a priority species in the Nottinghamshire Biodiversity Action Plan (BAP) and has legal protection under the amended Wildlife and Countryside Act.

2. WATER VOLE FEATURES

The water vole is the largest of the British voles with adults weighing 200 - 350gm. Males are usually slightly larger than females, although pregnant females are larger than the males. The water vole has a rich silky coat that is typically dark brown in colour, short round ears that are hidden in the fur of the head and nape, a rounded body and a blunt nose.It is often confused with the brown rat, which is slightly larger and has a pointed nose. The water vole's tail is about half of its body length and well haired, whereas the rat's tail is much longer and looks naked or scaly.

Although the water vole swims and dives well, it is not particularly adapted to water; it is very buoyant and swims high out of the water, doggy paddle style, and after prolonged submergence the fur becomes waterlogged.

When they enter the water they make a distinctive 'plop'. If you hear one look for the V-shaped wake that the swimming water vole makes in the water.

3. HABITAT

Water vole colonies tend to be found within two metres of water. The most common sites are vegetated banks of ditches, rivers, streams, canals, ponds, and marshes with still water or little flow, and where water is present all year round. Water voles prefer steep banks, as they are able to construct a network of burrow systems above and below the waterline. They will also weave nests of reeds and sedges in marshy areas. Water voles are active during daylight and early evening.

4. FOOD

Water voles are generally herbivores, eating most vegetation they can find, especially the lush stems and leaves of waterside plants. They will also eat invertebrates. A nation-wide survey was able to identify 227 species of plant eaten by the water vole in Britain (Strachan & Jefferies, 1993). In a day the water vole will consume approximately 80% of its body weight. Water voles often bring their food to chosen places near the water's edge to eat. The food remains, usually bits of chewed plants, are left in neat piles.

5. BREEDING

Water voles will have up to 5 litters per year, litter sizes ranging from 3 to 7 young. They are territorial during the breeding period, marking their territories with piles of green, 1cm. long droppings. These piles are called latrines.

The young are born between April and September, blind and helpless in a nest chamber made of grass. They will leave the nest at about four months. If the young are born before July they may breed that autumn, but most will reach sexual maturity after their first winter. They are less active and gregarious during the winter so winter mortality is very high, often up to 70%.

6. FURTHER INFORMATION

Changes in land use have resulted in habitat loss and the fragmentation or degradation of inter-connected water vole colonies. Losses have also been caused by poor management and flood defence work. This has led to an increased vulnerability to a surprising number of key predators, especially the aggressive North American mink. Unfortunately the water vole is a slow swimmer so it is very easy to catch.

Habitat preservation and creation can be achieved with the co-operation of landowners. Simple measures, such as spreading ditch clearance over a longer period or establishing a buffer strip between vole’s habitat and development can ensure their survival.

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