Vole Facts & Control 

Voles are small, mouse-like rodents that occur throughout most of North America. Though they commonly are called meadow mice or field mice, they are distinguished from true mice by their short tails (about one inch long), stocky build and small eyes (Figure 1).

Voles can cause problems by damaging lawns, gardens, tree plantings and other plants.

Figure 1. Prairie vole

Voles are an important food source for many predators, including snakes, hawks, owls, coyotes, weasels, foxes, mink and badgers. Mortality rates for voles are very high. Life expectancy in the wild often does not exceed two months, and few ever live longer than 16 months. Not surprisingly, voles are very prolific animals, although the pine vole is less so than meadow or prairie voles.

The breeding season for all voles encompasses most of the year although peaks occur in spring and fall. Prairie and meadow voles normally have five to 10 litters per year and average three to five young per litter. Pine voles have one to six litters per year and average two to four young per litter. The gestation period is about 21 days. One meadow vole held in captivity had 17 litters during one year, totaling 83 young. One of the females from her first litter had 13 litters, totaling 78 young before she was one-year-old.

Many vole populations are cyclic. In North America, population peaks occur about every four years. These are not necessarily regular cycles, nor do they usually involve spectacular population explosions. Occasionally, population explosions occur that last about a year before the population crashes. These peaks have resulted in severe crop damage problems.

Prairie and meadow voles inhabit pastures, roadsides, alfalfa fields and other grassy or weedy sites. Preferred habitats include areas with fairly dense ground vegetation. Meadow voles are more common in low, moist areas or upland sites near water. Pine voles live in timbered areas, underground or under the forest litter. They also inhabit fields surrounding timber, if enough ground cover is present.

Prairie and meadow voles construct surface runways that are easy to recognize by the closely clipped vegetation within them. Small holes lead to underground runways and nesting areas. Pine voles have extensive underground runway systems, and spend little time above the leaf litter and ground cover layer.

The three species of voles differ in color, general size and relative length of tail, but it usually isn't necessary to distinguish between the species to control the damage they cause.

Since pine voles spend almost all of their time underground, control strategies may need to be different from those for prairie or meadow voles. It may be easiest to determine if pine voles are suspect by the location of the damage (underground versus above-ground) and the lack of surface runway systems.

Probably the most extensive and costly damage caused by voles occurs to woody plants in winter. At times voles severely damage or kill many young trees and shrubs, including orchard, windbreak and landscape plantings (Figure 2). Voles will eat the green inner bark layer of trees and shrubs when preferred foods are unavailable.

Figure 2. Vole damage may severely damage or kill small trees.

Figure 2

Pine voles spend a much greater part of their time underground. and eat a much larger portion of roots and tubers than meadow and prairie voles. Voles also cause damage by clipping and feeding on other plants we . value. They eat leaves, shoots, roots, tubers and seeds of most grasses and broadleafed flowering plants. Voles can damage or consume flower bulbs, garden plants and vegetables, field crops and forage crops. Voles can damage lawns by constructing runways and clipping grass permanent, it may detract from the appearance of a well-kept lawn.

Signs found at the damage scene will help you identify the species at fault. The presence of prairie and meadow voles in an area usually is determined by finding their characteristic surface runways (Figure 3). The runways consist of closely clipped vegetation, about one to two inches wide.

Figure 3. Surface runway system of the prairie vole. 
Vole damage to woody plants usually occurs during late fall through early spring. During these months green vegetation is scarce, so voles feed on woody plants, which they prefer less. Voles tunnel through snow, and may gnaw on trees and shrubs up to the height that snow accumulates during winter. Individual tooth marks (about one-sixteenth inch wide) may be visible on the wood after winter vole damage (Figure 4). Rabbits leave tooth marks that are larger, about one-eighth inch wide. The gnawing marks left by voles will be irregular in appearance and at various angles. Pine voles, and occasionally meadow and prairie voles, tunnel below ground and feed on roots of trees and shrubs.

Figure 4. Vole toothmarks are about one-sixteenth inch wide. 
Voles occasionally will use tunnels developed by moles to gain access to flower bulbs and other plant roots. This damage often is blamed on moles by mistake. Moles feed on insects and earthworms and rarely consume plant materials 

Figure 4

The presence of voles does not always result in significant property damage. However, because of their prolific and cyclic nature, high populations can build up quickly and can be cause for concern.

Before undertaking control, consider the extent of the problem in relation to the cost of control. For example, a few voles could damage a highly valued tree or flower bed and warrant control. At other times, they may go virtually unnoticed, making control unnecessary.

Generally, there is a direct relationship between vole populations and the expected overall level of damage. Remember that damage prevention is more beneficial than population control after the damage has occurred..

Reducing the suitability of habitat for voles lessens the likelihood of future damage. High vole populations cannot become established without food and protection from predators. Grass and weeds can be controlled around young trees and shrubs through cultivation, herbicides and mowing. Normal cultural practices employed in establishing windbreaks, orchards and other woody plantings often are effective in reducing vole habitat and potential population highs.

When food and cover are nearby during the growing season, extensive damage still may occur to trees and shrubs where snow accumulates because snow acts as protective cover. Strategies other than habitat modification may be needed where high vole populations exist in the fall near woody plantings. 

Exclusion is a practical method of protecting highly valued flower beds, gardens and trees from vole damage. Voles can be discouraged by installing woven wire or hardware cloth fences (one- fourth inch or smaller mesh) around small flower beds or gardens. The fence should be about 12 inches high and the bottom should be tight to the ground or buried slightly. Where pine voles are a problem, the fence should extend about six inches below ground. Fences also help keep out other wildlife that cause damage, such as rabbits and ground squirrels.

Figure 5. A cylinder of hardware cloth or other wire mesh to protect trees from vole damage. 
Place woven wire or hardware cloth cylinders around individual trees or shrubs (Figure 5). Again, the cylinder should be tight to the ground or buried slightly, but should extend higher than the maximum snow depth in winter, including drifts. Where rabbits also are a potential problem, the height should be at least two feet above the snow depth, if possible. When making the cylinder, overlap the edges at least one inch and fasten securely so gaps do not form that could admit voles. These cylinders should last about five years, so make them large enough in diameter to accommodate expected trunk growth if they remain in place during the growing season. 

Figure 5

Various "hot sauce" repellents are registered for vole damage control on ornamental plants. They are not registered for use on gardens or plant parts destined for human consumption. 
Repellents are relatively expensive and provide only short term protection. Precipitation may wash some off. When foods are in short supply, such as in winter, the effectiveness of repellents usually decreases. 

Single trap set in vole runway, or two traps set back-to-back. 
Voles can be controlled easily by trapping if only a few are causing problems. Set single mouse snap traps perpendicular to vole runaways, with the triggers in the runways. Or, set two traps together within the runway, with the triggers facing away from each other . (Mouse Traps) Peanut butter mixed with oatmeal makes a good bait to place on the trap triggers. 

Reduction of large vole populations is accomplished most effectively with Baits

Bait may be applied by hand in spot treatments by placing bait in runways or burrow openings. Hand-baiting is the only application method that can be used in urban areas such as lawns, ornamental plantings, parks and golf courses. Toxic bait also may be broadcast-applied according to label directions. Broadcasting will increase the amount of bait applied per acre and the hazard to non-target wildlife. Use of toxic bait is most appropriate in young woody plantings or orchards, when habitat reduction efforts have failed to keep vole populations in control. Remember to read all pesticide product labels thoroughly and comply with all directions given.

Use pesticides safely. All toxicants and fumigants used to control voles can be hazardous to humans, pets, livestock and non- target wildlife if used improperly. 

As in most vertebrate pest situations, a combination of methods may be more effective than relying on any one method for vole damage control. Most vole damage problems in urban and backyard areas probably involve small vole populations that can be controlled with habitat modifications, fencing or exclusion, snap-trapping and repellents. Non-urban vole damage situations may involve larger vole populations over greater areas, and can be dealt with by habitat modifications, repellents, and lethal baits when necessary.

(Courtesy of Nebraska University and Colorado University)

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