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Meadow Vole and Pine Vole

 Tree Fruit Fact Sheet 102GFSTF-M1 1988

Authored by M. E. Tobin and M. E. Richmond. Photographs by M. E. Tobin and J. Ogrodnick (fig. 2). Published through the New York State Integrated Pest Management Program, New York State College of Agriculture and Life Sciences, Cornell University. Funded In part by the New York Cooperative Fish and Wildlife Research Unit. Cornell Cooperative Extension provides equal program and employment opportunities.


Microtus pennsylvanicus (Ord)
Microtus pinetorum (LeConte)

Introduction

Meadow voles occur throughout most of the northern and eastern United States and Canada in low wetlands, open grasslands, and orchards. Meadow voles are most active above the ground, as evidenced by surface trails often littered with droppings and grass cuttings in the ground vegetation where they live (fig. 1). They sometimes live underground where the soil has been cultivated or where a burrow system is already present.

Pine voles live throughout the eastern half of the United States and favor open woodlands and orchards. Pine voles spend much of their time in underground burrows and usually have an extensive subsurface trail system that is excavated about 3 to 5 cm (1 to 2 in.) deep. These burrows open to the surface and often connect to above-ground runways.  (top is meadow vole, bottom is pine vole)

Identification
The pine vole is a stocky little rodent with a blunt nose, short legs, and a tail that is shorter than the head-and-body length. Adult meadow voles are larger than pine voles, have longer tails, and have dark brown fur (fig. 2). A number of other physical, social, and ecological differences distinguish these two species (see table).

Damage
Both species cause substantial damage to commercial fruit trees and are pests of the home gardener and horticulturist. By girdling the trunk and roots, these rodents kill trees, reduce harvest yields, and prolong the time required for new plantings to come into production. Meadow voles usually girdle the trunks of trees at or above ground level (fig. 3). Pine voles commonly damage underground roots, making them look as though they were sharpened with a pencil sharpener (fig. 4). Pine voles can also girdle the crowns of trees at ground level, especially under cover of snow.

Management
Voles are prolific breeders, and their populations have the potential to irrupt every three to five years unless their numbers are controlled or the carrying capacity of the habitat is reduced. Mowing the groundcover reduces the availability of foods preferred by voles, removes cover that protects them from predation, and exposes the animals to the seasonal elements. Maintaining a bare strip underneath the canopy discourages voles from living near the base of trees. Wrapping 1/4-inch-mesh galvanized hardware cloth around the base of young trees (fig. 5) prevents meadow voles from girdling trees, although it does not prevent pine voles from girdling the roots and trunk below the mesh.

 

Distinguishing Characteristics of Meadow Voles and Pine Voles

 

 Characteristic

 Meadow Voles

Pine Voles

 length (head and body) 90 to 125 mm (3.5 to 5 in.) 70 to 105 mm (2.8 to 4.2 in.)
 tail 35 to 65 mm(1.4 to 2.6 in.) at least twice the length of the hind foot 15 to 25 mm (0.6 to 1 in.) less than or equal to the length of the hind foot
 adult fur coarse, dark brown mixed with black soft, auburn, lacking guard hairs
 eyes large  small
 ears large  inconspicuous
 nest usually above ground, but occasionally in shallow burrows in burrows, usually less than 3c cm (1 ft) deep
 sociality females maintain exclusive territories during breeding seasons:males are mobile family units maintain year-round exclusive territories
 food grasses, sedges, seeds, grain, bark, some insects bulbs, tubers, seeds,bark
 damage  girdle tree trunks at or near ground surface; may girdle higher under cover of snow; sometimes damage roots girdle crown and roots



Early detection and control of populations before they reach high levels is important. The economic threshold for voles is very low; any sighting indicates the need for control measures. Allowing populations to multiply increases the probability of damage to trees, makes future control more difficult, and can necessitate that greater amounts of poisonous bait be introduced into the environment.


Application of toxic bait is the quickest and most effective method for removing troublesome populations. Broadcasting baits across the orchard floor by hand, spreader, or airplane is the most common method of application. However, placing baits directly in runways and burrow openings may be a more effective way to control pine voles, especially when they confine their activity to below a heavy thatch layer or below thick vegetation on the ground.


In apple orchards, baits frequently are applied during the fall after the harvest. However, in some orchards, winter and/or early spring applications may also be necessary to control residual populations or reinvading animals. When conditions allow, winter applications may be particularly effective because 1) most girdling occurs at this time; 2) vole trails are readily apparent in melting snow (fig. 5); and 3) bait acceptance is likely to be greatest because preferred foods will be scarce.


Adherence to safeguards will foster efficacious use of toxic baits for the control of voles in orchards. Mowing the groundcover and raking away the vegetation, leaf litter, and other debris under the dripline helps to insure that the bait reaches the ground where voles can find it. Applying baits only when several days of dry weather are expected allows voles sufficient time to find and eat a lethal dose of bait before it decomposes. Alternating from one type of toxic bait to another forestalls or prevents the development of physiological resistance and bait shyness.

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Design & maintenance: Karen English-Loeb, IPM Program, Technical Wizardry: Cheryl TenEyck, IPM Progra.  All material is protected by Section 107 of the 1976 copyright law. Copyright is held by Cornell University and the New York State IPM Program.

 

Note:  This NebGuide provides information about voles, the damage they cause, and ways to prevent and control damage problems.  For graphics, see their web site below.

 

2.   University of Nebraska Cooperative Extension educational programs abide with the non-discrimination policies of the University of Nebraska-Lincoln and the United States Department of Agriculture.

Daryl D. Fisher, IPM Extension Assistant Vertebrate Pests
Scott E. Hygnstrom, Extension Vertebrate Pest Specialist

Voles are small, mouse-like rodents that occur throughout Nebraska. 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.

Vole Facts

The most common species, the prairie vole (Microtus ochrogaster), occurs statewide. Meadow voles (Microtus pennsylvanicus) are also nearly statewide in occurrence. Pine voles, or woodland voles (Microtus pinetorum), live in the woodlands of the extreme southeastern corner of Nebraska.

 

Figure 1. Prairie vole

Voles are small, weighing one to two ounces as adults. Their overall adult body length varies from three to five and one-half inches in the pine vole, to about four and one-half to seven inches in the meadow and prairie voles.

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 in Nebraska 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.

The exception may be for persons living in the extreme southeast corner of Nebraska who have problems with pine voles. 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.

Economic Importance

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.

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 forbs, or 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 very close to the roots. Though the damage done usually is not permanent, it may detract from the appearance of a well-kept lawn.

Damage Identification

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.

Controlling Damage

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.

Habitat Modification

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

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.

Repellents

Various thiram and "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.

Traps

 

Figure 6. 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 (Figure 6). Peanut butter mixed with oatmeal makes a good bait to place on the trap triggers.

Toxicants

Reduction of large vole populations is accomplished most effectively with toxic baits. Zinc phosphide is federally registered for vole or field mouse control. It usually is a Restricted Use pesticide that may be purchased and used by Certified pesticide Applicators only. Contact your local extension agent or information on becoming a Certified pesticide Applicator.

Some formulations of zinc phosphide are packaged in small containers and are registered as General Use pesticides. These may be purchased and used by the general public.

Zinc phosphide is available in formulated pellets or treated grain. Toxic 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.

Fumigation

Gas cartridges and aluminum phosphide tablets may be used to fumigate vole tunnels if they are labeled accordingly. Fumigation may not be very effective, however, since vole tunnels often are shallow and complex. Aluminum phosphide is a Restricted Use pesticide.

Safety Precautions

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. Only use products the Environmental Protection Agency registers for voles. Read pesticide product labels carefully and comply with all directions given. If needed, seek assistance from your county extension agent.

Integrated Pest Management

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 toxic baits when necessary.

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File G887 under: WILDLIFE MANAGEMENT
A-14, Animal Damage Control

Issued September 1988; 10,000 printed.