BIOLOGY: Voles, also known as meadow or field mice, have stocky, furry bodies, short legs, and short tails. There are 23 species of voles in the United States, but the two of greatest consequence to gardeners are the meadow and pine voles. Meadow voles (Microtus pennsylvanicus) have gray to yellow-brown fur with black-tipped hairs and a bicolor tail. They are five and a half to seven and a half inches long. They live mostly above-ground, traveling in one- to two-inch-wide runways in meadows, orchards, and old fields. These trails are particularly conspicuous shortly after snow has melted. Pine voles (M. pinetorum) have soft, dense, reddish brown fur, and their undersides are gray, yellow, or cinnamon colored. They can reach a length of four to six inches. Pine voles are subterranean rodents that create extensive networks of underground tunnels. Their typical habitat is the shrubby edge between woods and meadows.
Voles do not hibernate. They are active year round, day and night. Furthermore, they breed year round. Gestation periods are only three weeks, and litters can yield up to nine offspring, with the result that vole populations tend to increase rapidly.
SYMPTOMS: It is their prodigious appetite for vegetation that brings voles to the attention of gardeners. Voles feed on both the below- and aboveground parts of plants, consuming grasses, seeds, fruit, roots, tubers, and bulbs. Their chisel-like teeth produce irregular patterns of gnaw marks that are about an eighth of an inch wide. The most serious damage they cause is often to the bark of fruit trees and ornamentals, especially during the fall and winter months, when they may girdle and kill even well-established specimens. The damage caused by meadow voles tends to be above the soil line, while pine voles feed underground.
CONTROL: Hawks, weasels, snakes, and domestic cats are all predators of voles. However, they usually fail to keep vole populations in check. Because voles avoid exposed areas, keeping the grass mowed, removing weeds, and picking up other litter will reduce vole habitats.
Protect the trunks of young trees with a cylinder of wire or plastic during the winter months. This should extend from an inch or more below ground to the height of the snowline. Pulling the mulch away from the trunk will also reduce cover for voles.
Although fragments of sharp stone added to soil may deter some tunneling, the surest way to protect tulips, crocuses, and other valuable bulbs is to plant them inside a wire-mesh box made of hardware cloth.
Snap-type mouse traps can be used to trap voles in the fall and late winter. Bait the trap with a peanut butter-oatmeal mixture on the underside of the trigger and place it perpendicular to a burrow opening or at the bottom of a runway. Cover it with an inverted nursery pot. It’s very important that the trap be dark and that it operate freely. Set traps at 10-foot intervals and check them daily. Reset them until no voles are caught over a one-week period. Roden-ticides can also be used, but you must take precautions to prevent exposure to humans, pets, and other nontarget animals. They are most effective in the warmer months. Ask your local cooperative extension service agent for information about the kinds of rodenticides approved in your state.