Cornwall Mammal Group
Field Vole-(Microtus agrestis)
Order: Rodentia
Conservation:
Field voles are one of our most abundant small mammals, occurring across Cornwall, but indications from several sources are that numbers may be declining, possibly as a result of changes in agricultural practices. The field vole is not legally protected in the UK and has no conservation designation.
Recognition:
Field voles create
characteristic runs
through grassland
under cover. At
feeding sites they
may leave small
heaps of nibbled
grass stems 20 to
30 mm long cut at
45°, often with small
piles of 6 to 7 mm long cylindrical, green, odourless droppings. Voles an sometimes be heard squeaking loudly during their territorial disputes.
Field vole larder
Distribution:
The field vole is widespread but under-recorded across Cornwall, possibly because of confusion with the similar bank vole and lack of survey effort. Field voles are found throughout Great Britain and in south-west Ireland and from the Arctic south to the Pyrenees and as far east as Lake Baikal in Russia.
Records:
2007-2012: 192
2002-2007: 612
Pre-2001: 122
Total: 926
Probably the commonest UK mammal, the
field vole has a typical blunt-nosed chubby
vole shape with small rounded ears. The
rather shaggy coat is yellowish-grey and
paler underneath. Juveniles are generally
darker than adults. The tail is about one third the length of the body and is the same pale brown all over. Field voles tend to be a little larger than bank voles, at up to 40 g weight and a body length of up to 120 mm in their second year. Field voles and bank voles are often misidentified. The bank vole has a neater red/brown coat and the tail is proportionally longer, about half as long as the body. The bank vole’s tail is also darker above and paler below whereas that of the field vole is uniformly pale grey/brown. The
ears of the field vole are also noticeably
smaller. Field voles appear quite bulky
compared to bank voles, due not only to
their generally greater size, but also to
their longer coat.
Field voles occur in ungrazed grassy fields, open woodland, verges, dunes and heaths
where sufficient cover is available. A territory of up to 1000 m2 is defended by a
dominant male. The animals create a network of shallow burrows connected by
covered runs. The spherical nest is built from shredded grass in tunnels or at the base
of tussocks and has one or more entrances. They feed on grasses and herbaceous
plants and occasionally insects. Food is sometimes stored in burrows Unlike bank
voles, field voles rarely climb, or enter houses.
Breeding occurs from April to September and after a gestation period of about 21 days
a litter of 3 to 7 young is produced: these are weaned after about 4 weeks. Voles may
produce up to 7 litters each year and may live up to 2 years, although only 2% survive
15 months. Populations may rise rapidly during spring and dip in midsummer, possibly reflecting increased predation, before rising again in autumn. Densities of up to 100 per hectare can occur at the spring peak. Fluctuations in field vole numbers can have significant consequence for predator numbers and species such as barn owl and weasel often rise or fall with the success or failure of voles.
Field voles are one of Britain’s most abundant mammals and constitute an important food source for many carnivores. Owls, kestrels, stoats, weasels, snakes and foxes all rely on field voles for an important part of their diets. Domestic cats kill large numbers each year. Field vole numbers are thought to be declining as a result of changes in farming practices over the last 100 years. Increases in rabbit populations are also thought to be detrimental to field vole habitat by reducing grass cover. Voles are often controlled in forestry plantations where they can cause significant damage to young saplings by eating bark at ground level, although this is normally addressed by the use of tree guards.
Survey Methods:
Small mammal trapping. Cat kill surveys. Field searches for runs and latrines. Owl
pellet analysis.
During work to relocate slow worms in the path of the A30 bypass at Dobwalls, lots of large black squares of roofing felt were laid in order to attract the reptiles who enjoy the warmth and shelter. Many field voles
also took up residence and several took the opportunity to raise families in these desirable residences.
© David Chapman
Did you know?:
The field vole is also known as the common
field vole and the short-tailed (field) vole. Field voles are strongly territorial and use urine to scent mark their runways, but unfortunately for them this is visible in ultraviolet light and some predatory birds can see these urine trails.
© Tony Atkinson
