Importance

Voles, also known as field mice, are small brown rodents very common in yards and fields. Their presence is most often observed in the late winter and early spring right after the snow melts, when their grassy trails are laid bare and areas of dead grass appear. Voles do the most harm to small trees and shrubs when they chew on the bark, often hidden below winter snows.

Identification

Voles are a group of small, brownish rodents about the size and shape of a mouse. They have small ears and a short tail, which give them a “stocky” appearance. They spend a great deal of time eating grasses and roots and making trails. These surface runways are one of the easiest ways to identify voles. Usually seen in early spring just after snowmelt, a series of criss-crossing trails can be viewed on the surface. There may be larger patches of dried grass that function as storage areas for extra food and nesting materials.

Voles will also make small holes about 1 inch across and underground tunnels to get to tubers and bulbs. They will even use mole tunnels. This often cause moles to be blamed for eating roots, instead of the white-grubs they actually eat.

Vole damage may also be noticed on trees and shrubs where they have chewed through the bark very near the ground. The vole’s front teeth will leave ¼ inch side-by-side grooves in the wood.

Biology

Meadow vole

Jennifer Menken, Univ. of Minnesota

Redbacked vole

Jennifer Menken, Univ. of Minnesota

Minnesota has several species of vole, the most common being the meadow vole (Microtus pennsylvanicus) and the prairie vole (Microtus ochrogastor). Like most rodents voles have a short life expectancy but are very productive breeders. One female vole can have 5-10 litters in a year averaging 3 to 5 young. They may nest in shallow grass filled nests on the ground, or dig a small tunnel about 4-5 inches down to nest. Fortunately voles are a prime food source for many predators such as snakes, hawks, owls, foxes, and badgers. Vole populations cycle, and about every 3-5 years there will be a population boom. Mild winters with good snowfall can help to increase vole populations.

Prevention

Voles are extremely common and total prevention is probably impossible but general yard sanitation may help keep vole numbers down. Remove woodpiles and other debris from the ground that may allow hiding places for voles. Keep grass trimmed short and bushes trimmed up from the ground. Bird feeders are another attraction for voles and should either be removed or the ground kept very clean to keep vole numbers down.

Management strategies

Vole damage on juniper

Michelle Grabowski, Univ. of Minnesota

Vole damage on juniper

Michelle Grabowski, Univ. of Minnesota

While lawn damage is most visible in the spring it is rarely permanent. Simply rake up the dead grass and reseed the area. As the surrounding grass grows it will cover up the trails. Vole damage to tree bark is best prevented by encircling the tree with a light colored tree guard. The guard should be tall enough to reach above the snow line in the winter and the base should be buried in the soil or have a soil ridge around the base. Make sure that the guard is loose enough so that it doesn’t constrict the tree.

In small areas trapping may be an effective way of reducing vole populations. Standard mouse snap traps set along runways or near tunnels baited with peanut butter will catch some animals. You may want to cover the traps so that pets and children do not accidentally find them.

Large vole populations can most effectively be reduced with toxic baits. There are some pesticides available for home use. Be sure to read the label before you buy any pesticide and again before you use the pesticide. Vole baits should be placed inside bait stations to reduce the risk of non-target species ingesting the bait. Most pesticides recommended for voles are restricted and can only be used by Certified Pesticide Applicators. Contact your local Extension educators for more information about pesticide use.

Remember the voles are always there and for a great portion of the year they go unnoticed. In an average year it may not even be worth the effort to control the population.