Voles In Your Lawn and Landscape

Voles (Microtus spp.) are small mammals that occur throughout Missouri. Commonly called meadow mice, they are distinguished from true mice by their short tails (about an inch long), stocky bodies and short legs. Their eyes are small and their ears are partially hidden. They are usually brown or gray but can vary in color. Three species of voles occur in the state, the pine or woodland vole (Microtus pinetorum), the meadow vole (Microtus pennsylvanicus) and the prairie vole (Microtus ochrogatser). Voles are small, weighing 1 to 2 ounces as adults. Their overall body length varies from 3 to 5.5 inches in the pine vole, to about 4.5 to 7 inches in the meadow and prairie vole.

The breeding season for all voles encompasses most of the year although peaks occur in the spring and fall. Meadow and prairie voles normally have five to ten 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.

Pine voles live in timbered areas, underground or in forest litter. They also inhabit fields surrounding timber if enough ground cover is present. Prairie and meadow voles inhabit pastures, roadsides, alfalfa fields and other grassy areas such as home lawns and ruffs. Preferred habitats include areas with fairly dense ground vegetation. Meadow voles predominately occur in the northern portion of the state and are commonly found in low, moist areas or upland sites near water. Prairie voles are the most common species found throughout the state.

Meadow and prairie 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.

These three vole species differ in color and size. However, it usually is not necessary to distinguish between the species to control the damage they cause. The exception may be for persons who have problems with pine voles. Because pine voles spend most of their time underground, control strategies may differ from those for meadow or prairie voles.

Vegetation greater than 6 inches in height, snow cover, brush piles, leaves, and low-hanging limbs all provide excellent habitat protection. If there is good cover and high-quality food available during the growth period of the population, predators cannot keep up with the population growth and economic damage can occur.

Voles eat a variety of plants, such as forage grasses, legumes and crops. In horticultural plantings, including flower and shrub plantings, home orchards, lawns and gardens, voles can cause damage by eating flower bulbs, clipping grass stems, girdling stems of woody plants and gnawing roots. In late summer and fall, voles often store seeds, tubers, bulbs and rhizomes. In the winter they may gnaw on stems and bark, causing significant damage to ornamental and orchard plantings. Plants not directly killed may be more susceptible to diseases or die from water stress during periods of drought.

Voles also tend to live in colonies. A vole colony may have several den openings connected by a network of underground runways. The runs of the meadow and prairie voles are on the soil surface and lead to underground dens, while the runways of the pine vole are usually underground. Vole colonies consist of a pair of animals but more than likely will include several generations. A colony can have runways covering an area as large as a quarter acre.

Although voles have value in the natural world, homeowners and managers of valuable horticultural plantings may need to use measures to control damage from voles. This article will help you identify voles and the damage they cause. Besides providing information on controlling vole populations to reduce damage, this article also outlines early warning signs that you can use to prevent problems from becoming severe.

Characteristics of voles
Before initiating a vole control program, it is important to identify the species causing the damage. A brief description of the species’ physical characteristics, reproduction and ecology follows. Meadow and prairie voles have similar behavioral and ecological characteristics and will be discussed together.

Pine or woodland voles Physical characteristics

• Eyes and ears concealed
• Tail shorter than hind legs
• Fur reddish brown
• Slightly smaller than meadow and prairie voles (3 inches long, weighs 1 ounce or less)
• Lives and causes damage below the ground

Meadow voles and prairie voles Physical characteristics

• Eyes and ears visible
• Tail longer than hind legs
• Fur gray to dark brown
• Slightly larger than pine vole (3.5 to 5.0 inches long, weighs 1 to 2.5 ounces)
• Builds an extensive underground burrow system but spends considerable time and causes most damage above the ground

Integrated pest management for voles
Sound principles of integrated pest management (IPM) require that pest populations be monitored before any control measures are undertaken. Homeowners and managers of grounds with shrub and flower plantings can scout for vole colonies and runways, especially during the spring and fall.

Trapping for positive identification
Trapping is also an effective way to determine the species of vole present. A snap-type mousetrap used with a small piece of apple for bait works well. A peanut butter-oatmeal bait also works well. The trap should be placed under the shingle. To trap pine voles, some excavation will be needed to place the trap down on the run. Place the trap at a right angle to the run. Bend the shingle to form an arched roof over the trap so that the spring will clear the shingle (See above).

Prairie and meadow voles can be caught by setting traps at right angles to their runways or set back-to-back within the run. No excavation is needed because these species travel along surface runways (See above).

Controlling vole damage
Before initiating a vole control program, be sure to consider the extent of the problem in relation to the cost of control. Damage prevention is much more beneficial than population control after the damage has occurred.

Integrated pest management techniques include a combination of methods to prevent and control vole damage. Cultural practices, such as mowing and using herbicides to control competing vegetation can reduce the dense ground cover that serves as vole habitat. Although mulching with sawdust or wood chips is an important cultural practice for many ornamental plantings, remember this practice also provides habitat for voles. Good sanitation in the garden, orchard or lawn is essential. Remove unused garden crops and clear all fruit from the orchard floor. Piles of dead branches and brush should be burned, chipped or hauled away to eliminate rodent habitat.

Young trees can be protected by placing cylinders made from hardware cloth mesh (1/4 inch or less) around the stems. Bury the hardware cloth about 6 inches deep to keep voles from burrowing under the wire cylinder and to reduce potential damage (Left). However, these exclusion techniques are not always practical, nor will they protect the stem in all situations.

Trapping can be used to eliminate small populations of voles and is often the most practical and economical method to use around the home and in the garden. As mentioned earlier, bait the mouse snap trap with a small slice of apple or with peanut butter-oatmeal bait. Be sure to stake the snap trap down, as a vole is strong enough to drag the trap away if not adequately caught.

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 plants intended for human consumption. Repellents are relatively expensive to use and, at best, provide only short-term protection. Precipitation often washes off the repellent and re-application through the year is often necessary. When foods are in short supply, as in the winter, the effectiveness of repellents usually decreases.

Using rodenticides in home landscapes
The reduction of large vole populations is accomplished most effectively with toxic baits. A good rodenticide program can be both effective and economical for home gardeners as well as commercial producers when vole damage is severe.

Home gardeners and managers of horticultural landscapes should consider using one of the labeled anticoagulant rodent baits to control voles. Anticoagulants require multiple feedings to kill the animal. These rodenticides are usually safer around nontarget species, and bait shyness will not develop as the animal never associates a weakened condition with the bait. Currently, chlorophacinone formulated as paraffinized pellets (sold as Rozol Rat and Mouse Bait Pellets) is recommended for use by homeowners and managers of horticultural landscapes for controlling voles. Be sure to read and follow all label directions when using any rodenticide.

Bait placement and use of bait stations. Place 2 tablespoons of pellets under a covered runway or in an entrance hole that is actively used by voles. Establish these covered bait stations at 10-foot intervals throughout the infested area. Placing these baits in protected areas will attract the rodent to the station, prevent ingestion by nontarget animals and minimize exposure to the weather.

Bait stations can be made from 2- to 3- inch PVC pipe constructed in an L-shape or upside-down T-shape (See above). The horizontal pipe should be at least 12 inches long. Bait stations can also be made from rolled tar paper, mailing tubes, or similar durable materials.

After about five days, repeat the baiting. Repeat the baiting process only in those areas still showing vole activity.

Remember
All rodenticides are designed to kill mammals. Take all reasonable precautions to prevent exposure to humans, pets, and nontarget mammals, birds and fish.

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. Any mention or listing of commercial products or services in this publication does not imply endorsement by University Outreach and Extension nor discrimination against similar products not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine current product labels before applying any chemical. For assistance, contact your University Outreach and Extension Center.

Brad S. Fresenburg Extension/Research Associate - Horticulture

Robert A. Pierce,
Extension Fish and Wildlife Specialist - Department of Fisheries and Wildlife Science