By Dan Stein
Voles, also known as meadow mice, short-tailed mice and orchard mice, can be serious pests of gardens, crops and orchards. Voles are often confused with house mice, and sometimes with moles and gophers.
Before getting too excited about how to eliminate voles, remember that voles are an essential link in the food chain. They are a major part of the diet for many predators including coyotes, foxes, badgers, weasels, cats, gulls, and especially hawks and owls.1 Don't control them unless they are doing clearly unacceptable damage.
It is important to know that vole populations are often cyclical. They are notorious for going through unpredictable population cycles that occasionally spin out of control. In parts of the Willamette Valley of Oregon, vole populations in the winter of 2005 to 2006 rocketed to up to an estimated one million voles per acre.2 That adds up to 20 voles per square foot, an astounding and clearly unsustainable number. The following summer, hardly a vole was to be found. This was likely due to a lack of food and the spread of disease.2
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Vole control, especially on large acreages, can be a serious challenge. While total vole control may not be possible, you should be able to keep the numbers down to a level that is tolerable through a combination of pest control efforts.
When looking for signs of voles, search for their distinctive aboveground runways, often hidden by grasses and weeds, that connect underground burrow openings.3 Also look for burrow openings, which are roughly 1 1/2 to 2 inches in diameter.3 On trees, gnaw marks about 1/8 inch wide and 3/8 inch long found in irregular patches may be present.3 Remember to check for below ground damage by pulling soil away from tree trunks.3 In areas with winter snow, voles can do serious damage to tree trunks hidden under the snow pack.3
2. Removing or Reducing Vegetative Cover
Heavy mulch and dense vegetative cover encourage voles by providing food and protection from predators and environmental stresses.3,4 Mowing and frequent soil cultivation helps to make areas less suitable to voles, and makes it easier to monitor for voles.3,5 Where feasible, maintain weed-free buffer strips around gardens at least 15 feet wide.3,5 A 4-foot diameter vegetation-free circle around the base of young trees or vines can also reduce problems.3 Wood chips and paper mulches are not favored by voles. Nor is vetch, for those who want to use a winter ground cover.4
3. Vole Fences
Because voles are poor climbers, wire fences at least 12 inches high with a mesh size of 1/4 inch or smaller will help to exclude voles from gardens.3,5 These fences can either stand alone or be attached to the bottom of an existing fence.3 Bury the bottom edge of the fence 2 to 3 inches into the ground to prevent voles from tunneling beneath it.5 A weed-free barrier on the outside of the fence will increase its effectiveness.3
4. Tree Guards
Young trees, vines and ornamentals can be protected from girdling by installing cylinders made from hardware cloth, sheet metal or sturdy plastic around the trunk.3,5 Support the cylinders so that they cannot be knocked over or pressed against the trunk, and make sure they are large enough to allow for tree growth.3 Bury the bottom of the cylinders below ground level to ensure that voles cannot burrow underneath.3 In areas with snow, the guards should reach high enough so that they will remain above snow level.3,5 Check periodically to make sure voles have not gnawed through or dug under cylinders.3
Using simple snap-type mouse traps is often effective if the vole population is low enough and concentrated in a smaller area (an acre or less).1,3,5 Don’t skimp on the number of traps you use. Use at least a dozen for small gardens, though more is better.3
Trap placement is very important. Because voles rarely stray from their runways, it's crucial to set traps along their routes. Place baited traps at right angles to the runways with the trigger end in the runway,1,3,5 or use them in pairs with the triggers facing out in opposite directions.5 Check the traps every day, removing dead voles and resetting the trap springs as needed.3 Continue to trap in one location until no more voles are caught, and then destroy the runways and burrows.3 Traps can be baited with a little peanut butter and oatmeal mixture, but bait is usually not necessary.1,3,5
Be careful when handling dead voles because they can carry infectious diseases, pathogens and parasites.3,5 To be safe, wear plastic or rubber gloves when handling dead voles.3,5 Bury voles or dispose of them in a plastic trash bag.3
Methods NOT to Use
Baits can cause secondary poisoning to predators that eat poisoned voles and kill non-target creatures such as birds, so they should not be used. Commercial repellents have not been proven effective or practical for use against voles.3 Nor are burrow fumigants effective due to voles' shallow burrow system with many open holes. Electromagnetic and ultrasonic devices are also considered ineffective.3
More About Voles
There are several types of voles that can be found in the Pacific Northwest,6 although this page does not go into detail on the various species. Voles are mouse-like rodents with compact, heavy bodies, short legs, short-furred tails, small eyes, and partially hidden ears.1,3 They have long, coarse fur that is grayish to blackish brown.1,3 A fully grown vole can measure about 4 1/2 to 7 inches long, including the tail.1,3,5 Voles differ from house mice in that they are larger and have shorter tails and smaller ears.
Voles spend most of their time belowground in their burrow system but establish aboveground runways that connect burrow openings.3 These runways are usually hidden beneath a layer of grass or other ground cover.3 There are usually multiple burrow openings about 1 1/2 to 2 inches in diameter that lead to a shallow tunnel system just below the ground surface that is used for feeding on plant roots.1,3 A deeper set of burrows is used for food storage, nesting and rearing young.
Biology & Behavior
Voles can begin breeding after only about 4 weeks of age3 and produce 3 to 6 offspring per litter, with anywhere from 1 to 10 litters per year.1,3,5 Species of voles that live at higher elevations have shorter breeding seasons. The gestation period is three weeks.1,5 Their life span is generally about 2 to at most 16 months.3,5 Voles are active year-round during the day and night, but they are most active at night.1,3
Several adults and young voles may occupy a burrow system.3 Their home range is usually only a few hundred square feet.3 Voles feed on a variety of grasses, herbaceous plants, garden crops, stems, seeds, bulbs and tubers.1,3,5 They will also damage trees by eating their bark and roots, especially in the fall or winter.1,3
Voles cause damage by their feeding, especially when numbers are high. They gnaw on the bark and roots of trees, including fruit trees, and if they completely gnaw around it will cut off the plant's nutrient's supply- called girdling.1,3 Damage to tree trunks can be seen a few inches above and/or below the ground surface. Look for irregular gnaw marks at various angles on the tree trunk.3,5 In areas where there is snow, damage to trees can extend a foot or more up the trunk and cause serious damage.3
The Bigger Picture
The narrow confines of this article portray voles mostly as pests. But, please remember the importance of voles in the ecosystem. Low population levels generally do no appreciable damage to human crops and gardens. Remember not to be in a hurry to kill them. Even when populations skyrocket, nature usually brings numbers back into control without the need for any human intervention.
- Gunn D, Hirnyck R, Shewmaker GE, Takatori S, Ellis LT. Meadow voles and pocket gophers: management in lawns, gardens and cropland, PNW 627 [Internet]. Pacific Northwest Extension; 2011 Jun [cited 2021 Mar 16]. Available from: https://catalog.extension.oregonstate.edu/pnw627
- Penhallegan R. Personal communication. 2006 Oct 12.
- Salmon TP, Gorenzel WP. Pest notes: voles (meadow mice), Publication 7439 [Internet]. UC Statewide IPM Program; revised 2010 Jun [cited 2021 Mar 16]. Available from: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7439.html#IDENTIFICATION
- Sullivan T, Granatstein D. Influence of living mulches on vole populations and feeding damage to apple trees [Internet]. Crop Protection: 108; 2018 [cited 2021 Mar 30]. Available from: https://www.researchgate.net/publication/324091065_Influence_of_living_mulches_on_vole_populations_and_feeding_damage_to_apple_trees
- Vantassel SM, Hyngstrom SE, Ferraro DM. Controlling vole damage, G887 [Internet]. Lincoln (NE): Univ of Nebr Coop Extension; 2011 Sept [cited 2021 Mar 16]. Available from: https://extensionpublications.unl.edu/assets/pdf/g887.pdf
- Oregon Dept. of Fish and Wildlife. Rats and mice [Internet]. Salem (OR); undated [cited 2021 Mar 30]. Available from: https://myodfw.com/wildlife-viewing/species/rats-and-mice