The bank vole is a small plump animal with a characteristic blunt vole face and small round ears. It has chestnut brown fur fading to grey on the belly. The tail is dark on top and paler below.
Males and females are similar in appearance but the young animals have greyer fur. The adult vole weighs up to 40 g and the body is about 90 mm long with a tail about half as long again.
Four subspecies are recognised in islands around the UK which all tend to be larger than the mainland race. Voles differ from mice in their blunt faces, less prominent ears, and shorter tails. Compared to the similar field vole, the bank vole has neater, redder fur, larger ears, and a longer tail which is noticeably darker on top.
Did you know?:
The bank vole has had its scientific name changed several times and was previously known as Chlethriomys arvicola and Euotomys glareolus. Kestrels are able to see into the ultraviolet spectrum and can detect bank voles’ urine trails, as the urine absorbs ultraviolet wavelengths, this allows them to focus on areas where voles are active. The word vole derives from the Norse vollmus meaning field mouse (rather confusingly!).
Bank voles living on abandoned tin mining sites in Cornwall and Devon have been shown to have high levels of arsenic in their tissues. Their position at the bottom of the food chain suggests that our mining heritage may still have an impact on Cornwall’s wildlife.
© David Chapman
Bank voles occur in a variety of habitats where sufficient dense cover is available,
typically deciduous woodland, hedgerows and banks. In winter bank voles may enter
houses and set up home in roofs and wall cavities. Males and females occupy territories that vary with season, breeding and food availability.
Bank voles are active throughout the day and night as they search for a range of grasses, seeds, berries, nuts and fungi. Voles can cause considerable damage to forestry plantation through bark stripping. They occasionally eat insects and birds’ eggs and often climb trees and shrubs to forage. In the autumn and winter they may collect and store food, carrying seeds in their cheeks in a similar fashion to pet hamsters. The bank vole’s feeding habits can provide useful information for surveys, with the characteristically opened hazel nuts providing definitive evidence of their presence.
Bank voles breed from April to October, although in mild conditions they may breed throughout the year and numbers may build rapidly to produce vole plagues which are then associated with increased numbers of predators such as short-eared owls. Building a spherical lined nest in short tunnels or under cover, the female can raise between 4 and 5 litters of 3 to 5 young each year. The young are weaned at 3 weeks and are sexually mature in a further 2 weeks. Few animals survive longer than 18 months and populations rise and fall dramatically over the year.
Bank voles are preyed upon by a wide range of larger animals - weasels, stoats, foxes,
owls and raptors, crows and adders. Domestic cats kill large numbers. Snow cover can
protect voles from predation in the winter. Voles are vulnerable to environmental
pollutants and also to changes in habitats brought about by development, farming,
road building and even increased grazing by deer.
© JB & S Bottomley
Small holes (about 30 mm diameter) in banks mark bank vole burrows. Bank voles may dig shallow tunnels just beneath the surface of lawns in damp conditions. Droppings are rarely seen outside the burrows and the small tracks are not diagnostic, but feeding signs such as the opening of hazel nuts (leaving a clean-edged hole with perpendicular tooth marks) and the stripping of tree bark at low levels are useful indicators of vole presence.
Small mammal trapping, owl pellet analysis and hazelnut surveys all provide specific information. Cat kills and other incidental sightings from bird feeders and mouse traps also provide records.
Bank voles are one of the commonest mammals in Britain with a population estimated at 25 million: they are not regarded to be of conservation concern. However, their short life span and dramatically fluctuating populations over the year may make them vulnerable to environmental or habitat change. The bank vole is an important component of the food chain for many predator species, which may themselves be vulnerable.
The bank vole is common throughout Cornwall, although probably under-recorded. More extensive field surveys are needed to establish the distribution of this important, but often overlooked, rodent. It is found throughout northern and central Europe, mainland UK and southern Ireland.