Water Vole Biology and Species Information

Family, Appearance and Lifestyle

The water vole is the largest of the British voles, weighing up to 350g. It is characterized by a rounded body, blunt muzzle and short ears but is not well adapted for life in the water, having unwebbed feet. Water voles in Britain are usually chestnut in colour but black variants are known in Scotland.

Range, Habitat, Territory and Home

The water vole is found across mainland England, Wales and Scotland but is absent from Ireland, the Isle of Man and the Scottish islands. Water voles live in linked colonies and are confined to the banks of watercourses, using runs through dense vegetation along the water’s edge to move around above ground. A series of burrows along the banks of rivers, streams and ditches provide shelter, nest chambers and storage for food. A population is only sustainable if a number of colonies is linked together.

Activity and Social System

 Water voles are good swimmers and divers and usually live in small groups. They are much more active in the summer than the winter when they spend much of their time underground. Adult water voles are territorial in the breeding season and mark their territories by scent.

Food

Water voles are largely herbivorous and feed on bankside vegetation, some invertebrates and carrion during the summer, stored food, roots and bark during the winter and any available fruits in the autumn. During pregnancy, water voles may also feed on flowers and freshwater molluscs, probably as a source of protein.

Breeding – mating, season, numbers

Breeding begins when day length increases, around March, and continues until October when the day length begins to shorten significantly. Females typically produce between 2 and 5 litters of 5-8 young per year and, if born before July, the young may breed during their first year. Juveniles are only likely to survive their first winter if they have attained a weight of at least 170g and mortality is high amongst dispersing juveniles. However, a rapid reproductive rate allows this species to survive following high levels of mortality during the winter months.

Threats

Large areas of habitat suitable for water voles were lost during agricultural intensification that followed the Second World War and further industrial development has led to fluctuating water levels and pollution that directly impact on water vole populations. Although water voles have developed extensive anti-predator behaviours, predation by the semi-aquatic American mink has led to the loss of entire colonies of water voles in a short space of time.

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