Mice (house mice and deer mice)

About

Small seed-eating rodents that move into gardens, sheds and homes, especially in fall and winter. They dig up planted seeds, eat bulbs and low-hanging produce and gnaw the bark of young trees, and deer mice carry hantavirus, so handle their droppings with care (UConn, UC IPM).

Spotting it

Damage

Mice dig up and eat planted seeds, including melon seeds, bite into ripening tomatoes, cucumbers, beans and peas that hang near the ground, and hollow out potatoes, carrots, beets and parsnips (UConn, UC IPM). Under snow they dig for seeds and bulbs and gnaw the bark and roots of young trees and shrubs; in a USDA study, house mice killed over half the young cottonwood seedlings penned with them (UConn, USDA).

How to find it early

Look for small dug holes along seed rows, gnawed fruit near the ground and tiny droppings. Deer mice have white bellies and feet, big eyes and ears and a two-tone tail; house mice are gray-brown with a nearly hairless tail and a mousy smell (UC IPM, UConn). Voles have their own page.

When

Year-round; garden damage is worst at seeding time and in fall and winter.

Life cycle

Deer mice have litters of three to six young, can breed at six weeks old, and breed mostly outside winter, or year-round where it's warm; few live past two years. They don't hibernate, and they stash seeds in fall (UC IPM).

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Remove cover Prevent

   Clear overgrown weeds, brush, hedges and wood piles near beds and buildings. This cuts numbers but won't get rid of mice (UC IPM).

2. Seal sheds and the house Prevent

   Close gaps larger than 1/4 inch with metal or concrete, since mice chew through plastic, foam and wood; steel wool works as a temporary plug (UC IPM).

3. Clean up droppings safely Prevent

   Air out a shed or garage for at least 30 minutes before cleaning. Wearing rubber or nitrile gloves, soak droppings and nests with disinfectant or a bleach solution (1 1/2 cups bleach per gallon of water), wait about 10 minutes, then wipe them up (UC IPM).

   Never sweep or vacuum dry droppings; the dust can spread hantavirus (UC IPM).

4. Cage seedbeds and young trees Barrier

   Cover seeded flats and beds with 1/4-inch wire mesh with the edges buried a few inches, or with upside-down plastic berry baskets. Stake or trellis peas and tomatoes so fruit stays off the ground, and guard young trees with wire set 1/2 to 1 inch away from the trunk (UConn).

5. Snap traps Trap

   Bait snap traps with peanut butter, oatmeal or sunflower seeds, set several along walls and at right angles to runways, and check them daily (UConn, UC IPM).

   Wear gloves and keep set traps where children and pets can't reach them. Don't use glue boards or live traps for deer mice, which raise the risk of hantavirus exposure (UC IPM). This guide does not recommend poison baits, which put pets, children and other wildlife at risk; UC IPM notes none are registered for deer mice around homes. Rules on trapping wild animals differ from state to state, so check with your state wildlife agency if you're unsure.

6. Skip repellents and gadgets Repellent

   UC IPM says ultrasonic devices and chemical repellents don't work against deer mice, and UConn says no repellent has fully solved a mouse problem.

7. Predators help a little Natural enemies

   Cats and other predators catch some mice but rarely control them on their own (UC IPM, UConn).

Plants it goes after

Beet, Blueberry, Cantaloupe (muskmelon), Carrot, Cucumber, Green beans (snap beans), Nanking cherry, Parsnip, Peanut, Peas, Potato, Ranunculus, Rose (garden and landscape roses), Saffron crocus, Salsify (oyster plant), Tomato, Watermelon

Pressure by region

The deer mouse is one of the most widespread mammals in North America (UC IPM). No regional severity source was found, so all ratings are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.