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October 3, 2009

What to Do About Wild Mice

The house mouse lives in homes and requires serious attention to prevention so that they do not become problems

Adapted from the book Wild Neighbors

house mice

Kelly Tipton/Sibley Nature Center

House mice came to American along with the first European settlers. They prefer to spend their lives inside buildings including homes, barns, warehouses, and offices. Wild mice such as the native white footed mice and deer mice would rather spend just the colder months indoors.

If all mice did was eat some of our food, we could probably live with them. But because they can be carriers for diseases, we are better off using humane techniques to prevent them from moving in with us.

 

Common problems and solutions

Public health concerns
Resources

Common problems and solutions

In large numbers, mice can and will eat lots of stored seed and grains. But the amount of food they eat will be much less than the amount contaminated with urine and feces.
Mice can also cause property damages by chewing wood, paper, cloth, books, and insulation on wiring—you’ll see tooth marks about 1/8 inch wide on the chewed materials.

Detecting Mice

Here are some tell-tale signs:

  • Small holes chewed through bread, cookie, or pet food bags.
  • Nests loosely made of paper, cloth, twine or other material in little-used drawers or cabinets.
  • Droppings that resemble small black grains of rice.
  • Cats and dogs showing particular interest in bare walls, closets, or appliances.
  • A cache of pet food found in a duffle bag stored in the closet.

Tolerance

Sometimes people live with mice for years and don’t even know it. Other times, they’ll know the mice are there and don’t mind them. And there are those times when the discovery of a mouse requires immediate attention.

Native white-footed and deer mice, who move indoors during the early fall or winter, usually can be humanely live-trapped and returned to the outdoors. House mice would probably not do well if turned out, but many people are willing to try relocating them rather than killing them with traps. If you can move the housse mouse or mice to a protected outbuilding such as a shed or garage, you’ll be giving them a better chance of survival.

How to keep mice out

Mice can enter buildings through openings no larger than the size of a dime. Keeping them out of buildings can be a difficult, long-term process. But it is the only effective way to permanently deal with mouse problems.

Carefully look for possible entry points:

  • Around foundations.
  • Where utility pipes and wires pass into the house.
  • Where siding has deteriorated and holes occur.
  • Cracks in foundations.

Sprinkle baby powder or flour lightly along the inside perimeters of walls and thresholds to see if there are any tracks. This will tell you where mice are active and what openings must be closed.

Now, close the openings:

  • Plug cracks around drainpipes and small openings with wire mesh or quick-drying cement. 
  • The best way to seal openings that don’t involve electrical wiring is a copper mesh pan scrubber.
  • Ball up galvanized window screen and stuff it into larger openings, then finish with caulking or cement.
  • Fill small openings with expanding-foam insulation.

Note: Don’t use caulk or other rubber or plastic fillers because mice can easily chew through them.

Habitat modification

Indoors
Keep your house free of obvious and not-so-obvious places to find food:

  • Breadcrumbs under the toaster.
  • Spilled food that is left on the counter or table overnight.
  • Spilled birdseed in the garage or shed.
  • Dry pet food left in the garage overnight or next to an appliance, behind which  mice can move unnoticed.
  • Pet food left out in the pet’s dish overnight.
  • Any food that isn’t stored in a metal or glass container.

Throw away food at the first sign that mice have gotten into it.

Outdoors
Keep flowers, shrubs, and hedges trimmed at least 18 inches out from the foundation of the house or building to be protected. This will also make it easier to find entry points.

Live Trapping

There’s a large variety of live traps at hardware stores or on the web.

Keep in mind a mouse who comes from generations of mice who have been born and only lived indoors isn’t likely to do well outdoors. There is every reason to believe that the chances that a live-trapped indoor mouse will survive outdoors are very low.

Lethal Control

People probably kill more rodents each year than any other wild animal. Most likely the killing isn’t followed by the habitat modification, sanitation, and exclusion necessary to provide a long-term solution.

The simple rule is: lethal control can never be justified without a diligent effort to apply other controls to prevent the recurrence of problems.

Unacceptable methods
Poisons and glue boards are cruel. They are less humane than snap traps, or the traps that use electricity to kill rodents.

The bottom line: There are no truly humane ways to kill mice, only some that are less inhumane.

Public health concerns

Mice can carry a number of diseases that humans can catch:

Resources

» Purchase a copy of Wild Neighbors; the go-to guide for useful, humane solutions to conflicts with wildlife
» If you are located within the D.C. Metro Area, take advantage of our wildlife conflict resolution service. Learn More

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