Identification and Control of Mice and Voles

In Connecticut, there are several kinds of mice and voles that may cause damage to gardens, fruit and other plantings: house mice, (Mus musculus); white-footed mice and deermice, (Peromyscus sp.); meadow voles, (Microtus pennsylvanicus) and pine voles (Microtus pinetorum). (see vole photos)

Mice and voles are more common than moles (burrowing, insectivorous, nearly blind and furry mammals), shrews (related to the moles and distinguished from them and the mice by a long pointed snout and very small eyes) and rats (larger than mice, with total body length from 15 to 17 inches).

General Physical Characteristics

There are also differences among mice and voles. House mice are tawny to dark gray on the back, gradually changing down the sides to ashy gray on the abdomen. Their feet are shorter, broader and much darker than those of white-footed mice. Their tails are as long as their bodies but are shorter and less hairy than white-footed mice tails.

White-footed mice, the most common species, and deermice have white feet and abdomens, large ears and eyes, and tails as long as their bodies. The color of the sides and back of these mice varies from dark gray to nearly black. They weigh 50% more than house mice and lack the mousy odor of house mice.

Meadow voles, commonly known as meadow mice, are stocky with small, but prominent, beady black eyes and almost concealed ears. Their short tails are about twice as long as their hind feet. Meadow voles are five to seven inches long at maturity and weigh twice as much as house mice. Their dense, shaggy fur is gray to brown with gray underparts, sometimes mixed with yellow or buff.

Their close relative, pine voles or pine mice, have smaller bodies, shorter tails, sunken eyes and underground burrow homes. Pine voles feed on plant roots and crowns.

Mice

In general, mice can cause much damage because of their physical capabilities. They are excellent climbers and swimmers. House and white-footed deermice can run up almost any vertical, roughened surface and climb and balance on wires. Their chewing of electrical wires may start fires. Mice can jump one foot straight up, live in temperatures as low as 14 degrees F and squeeze through an opening slightly larger than 1/4 of an inch. Their sense of smell in acute. In six months, a pair of house mice can eat about four pounds of food while excreting some 18,000 fecal droppings or pellets. Although mice are not blind, they do have poor vision and are unable to see clearly beyond six inches.

In considering control measures for mice, it is important to know where they live and how they feed. Mice live in grassy or bushy areas, nesting underground in shallow burrows or aboveground in densely vegetated or protected areas. Also, they can build nests in thick hay or leaf mulches in the garden or cropping areas. Nocturnal feeders, mice are active throughout the year. They forage along narrow surface runways from their nesting areas to their sources of food. In addition, they travel and feed underground via old mole tunnels.

The bark and roots of young trees are gnawed and severely damage by mice. Ripening tomatoes, cucumbers, beans, peas and other fruit close to the ground are bitten into. Developing roots or tubers of potatoes, carrots, beets and parsnips are dug into and eaten by mice, as well. Mice often invade homes or sheds in the fall. In wintertime, their runways are made below the snow cover where they dig up and eat seeds, nuts and bulbs. They feed on tender bark and foliage of shrubs, roses and small fruits such as blueberry.

White-footed and Deer Mice

White-footed mice are commonly found in diverse habitats including open, grassy, brushy and wooded areas. They spend the winter as a family group in a nest made of stems, leaves, sticks and roots and lined with fur, feathers or shredded cloth. Nests are found underground or in protected areas such as old burrows, under boards, hollow logs or buildings. Breeding occurs from spring to fall, with two to four litters of one to eight young per year. Mice born in spring or summer may breed that same year. White-footed mice feed in an area from 1/3 to 4 acres.

Control

With the characteristics and habits of mice in mind, plan your control program. Here are some helpful pointers:

  1. Use good cultural methods to enable planted seed to grow as quickly as possible.
  2. Newly-seeded flats and seedbeds can be protected by placing 1/4 inch wire mesh cages or small plastic strawberry-type baskets over seeded areas. In the field, make sure edges are buried several inches into the soil. Cages can be made large enough to protect small trees, blueberries and other shrubs. Cages should be at least 1/2 to one inch from the trunk.
  3. In the field, stake, trellis or cage plants such as peas or tomato to keep the fruit off the ground.
  4. Common snap-back mouse traps are effective to eliminate mice in homes or structures. Bait with oatmeal, peanut butter, cheese, sunflower seed, moistened rolled oats or cotton balls (for nesting material). Use many traps, check them daily, rebait and reset as needed. Traps should be placed along the sides of runways and perpendicular to the runways. Gloves should be worn when setting traps to reduce human scent. Placing unset baited traps in runways for several days to allow mice to become accustomed to them may increase effectivness when they are set
  5. Anticoagulant baits (warfarin, diphacinone, chlorophacione, brodifacoum and bromadiolone) are labeled for control of certain mice. Read and follow all label directions and precautions. If misused, these baits can be harmful to domestic animals. These baits are most effective when used within a bait box, which is commercially available at garden and agricultural supply centers.
  6. Grain baits contain restricted use pesticides and are not currently labeled nor recommended for vegetable crop areas.
  7. In out buildings, such as barns, cats have been a popular method of mouse control for a long time.
  8. Although mice have an aversion to some odors and tastes, at present no repellents have been found to solve a mouse problem completely. The use of frightening sounds is not effective in field situations.

Damage By Voles

In Connecticut, meadow voles are more abundant and destructive than pine voles. Although damage to fruit tree root systems by pine voles often results in serious economic loss to fruit growers, for the purposes of this fact sheet, we will focus on meadow voles. Meadow voles eat a wide variety of crops and plants, with a preference for grasses. When vole populations are high, many field crops are eaten. Their extensive tunnel systems cause root destruction and interfere with crop irrigation, as well. In late summer and fall, voles store seeds, tubers, bulbs and rhizomes in their tunnels.

Life History

Voles are active day and night the entire year. They construct a complex tunnel system with surface runways and numerous burrow entrances. A single tunnel system may contain several adults and young.

Voles have short life spans, ranging from two to sixteen months. Breeding occurs primarily in spring and summer, producing from one to five litters of three to six young per year. Females mature in 35 to 40 days.

Control

The following suggestions will help in vole control:

  1. Eliminate weeds, ground cover and crop litter in and around cultivated areas. This reduces they availability of food and cover for voles, and the capacity of these areas to support them.
  2. Permanent sod strips between blueberry or raspberry rows must be mowed regularly. A weed-free or vegetation-free strip is an excellent buffer around areas to be protected. The wider the buffer strip, the less likely voles will cross it to the cropping area.
  3. Frequent tillage removes cover, destroys existing runways or tunnels and destroys a percentage of the existing population.
  4. Several chemicals, such as zinc phosphide and Rozol baits are effective for fall and winter vole in noncrop areas. Rates and method of application vary. Read and follow all label directions and restrictions. Zinc phospide is a restricted use pesticide.
  5. Wire or metal barriers (tree guards) at least 12 inches high, with a mesh size of 1/4 inch or less around blueberries or trees, will exclude meadow voles. Bury the bottom edge six to ten inches to prevent pine voles from digging beneath the barrier.
  6. Mouse traps, or snap-back traps, can be very effective in reducing the vole population. Place the trap perpendicular to the runway with the trigger end in the runway. Apple slices or a peanut butter-oatmeal mixture make good baits.
  7. A section of roofing shingle placed over the burrow opening and baited with an apple slice will attract voles. A trap can also be placed under this shingle, as voles are readily attracted to shingles or pieces of plywood placed on the ground. Shingles should be bent to form an A-shaped root. Plywood or flat material should have small blocks under the corners to allow for a crawl space. These shelters can also serve as bait sites. Leave in place a few days before baiting to allow the animals to become accustomed to it.
  8. At least one repellent utilizing thiram (Bonide Rabbit, Deer and Field Mice Repellent) is labeled for voles. Also, a new material, Miller Hot Sauce Animal Repellent, containing the extract capsaicin from peppers, may afford short-term protection from meadow and pine voles. The label states use on ornamentals, fruit trees, vines, bushes and certain vegetable crops (beans, peas, peppers, melons, squash and tomatoes). Check the label for mixing directions and use restrictions.
  9. In general, fumigants are not effective due to the complexity and shallowness of vole tunnel systems. Frightening agents have not proven to be satisfactory controls.
Prepared by Norman Gauthier, Cooperative Extension Educator/Entomologist, University of Connecticut

The information in this material is for educational purposes. The recommendations contained are based on the best available knowledge at the time of printing. Any reference to commercial products, trade or brand names is for information only, and no endorsement or approval is intended. The Cooperative Extension system does not guarantee or warrant the standard of any product referenced or imply approval of the product to the exclusion of others which also may be available.All agrochemicals/pesticides listed are registered for suggested uses in accordance with federal and Connecticut state laws and regulations as of the date of printing. If the information does not agree with current labeling, follow the label instructions. The label is the law.Warning! Agrochemicals/pesticides are dangerous. Read and follow all instructions and safety precautions on labels. Carefully handle and store agrochemicals/pesticides in originally labeled containers immediately in a safe manner and place. Contact the Connecticut Department of Environmental Protection for current regulations.The user of this information assumes all risks for personal injury or property damage.Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kirklyn M. Kerr, Director, Cooperative Extension System, The University of Connecticut, Storrs. The Connecticut Cooperative Extension System offers its programs to persons regardless of race, color, national origin, sex, age or disability and is an equal opportunity employer.

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