House Mouse Prevention and Control

  • Published
  • By 23rd Civil Engineer Squadron
  • Department of Entomology
The house mouse (Mus musculus) is considered one of the most troublesome and economically important pests in the United States. House mice live and thrive under a variety of conditions in and around the work place and homes. House mice are commensal meaning they live with or in close association to humans eating or contaminating food that is meant for humans or pets. They contaminate food preparation surfaces with their feces, which can contain the bacterium that causes food poisoning (salmonellosis) and have been known to carry over 200 diseases. Their teeth grow continually, like human fingernails, so they must constantly gnaw to keep them from getting too long.

Recognizing a mouse infestation

Because mice are nocturnal, they often reside in a building for some time before being discovered. If you happen to see a mouse during the day, it is usually a sign that there are a significant number of mice in the area. Here are some of the more common signs that mice are living nearby:

1. Mouse droppings
  • a. Mice deposit 50 - 75 fecal pellets each day
  • b. Droppings are about 1/8 to 1/4 inch long ( resembling a black grain of rice)
2. Gnaw marks
  • a. Gnaw marks will be about 1/32 inch wide
  • b. Mice typically gnaw 1 ½ inch wide holes in cardboard and similar materials.
  • c. Marks will often appear on food containers and food packages
3. Musky odor
  • a. House mice and their urine have a very particular musky odor
  • b. Odors are often found in cupboards or drawers
  • c. Rats do not have the same odors as mice
4. Scratching or squeaking sounds from walls and ceilings
  • a. Mice are known to have caused structural damage by chewing on wood.
  • b. They will also chew through wires and use insulation to make nests
5. Mouse nests
  • a. They are usually made from fine shredded paper or other fiber material such as dryer lint or insulation
  • b. Nests are normally found in sheltered out of the way locations
If you're not sure whether or not you have mice, try this test. Place a cracker or a piece of bread with peanut butter on the floor next to the wall and scatter flour or talcum powder around it. Leave it over night and check for tracks in the morning.

Step 1: Make your building less mouse friendly

Like any other creature, mice need food, water and shelter to survive. Taking steps to provide less opportunity to find these things is one of the best ways of reducing the mouse population. Start by searching in areas that are within 50 feet of the building for any food sources or hiding places. Although good sanitation alone will seldom eliminate mice, poor sanitation is sure to attract them and will permit them to thrive in greater numbers. Good sanitation reduces food and shelter for existing mice, in turn making baits and traps more effective.

Food and Water Sources

1. Do a thorough cleaning of the building. Vacuum or sweep under furniture and furniture cushions, behind and underneath appliances and in and behind cabinets.
2. Place trash and garbage in a tightly covered trash can
3. Feed dogs and cats from dishes and remove any food they don't eat
4. Wash and put up all dishes before going to bed each night.
5. Wipe down stoves, counters and tables to remove any crumbs or spilled food
6. Sweep/vacuum floors to remove any spilled food
7. Place any bird feeders up off the ground and away from the building
8. Store mouse attractive food in rodent proof containers (metal or glass are best) or in the refrigerator
9. Fix any leaking plumbing, dripping faucets etc. that give mice access to water.

Shelter Sources

1. Recycle newspapers, paper bags and cardboard rather than letting it pile up
2. Remove any overgrown shrubs, foliage or vegetation from around the building.
3. Remove clutter from attics, closets, basements, crawlspaces and garages
4. Remove trash, old boards, weeds and any clutter where mice can hide
5. Don't pile wood, lumber pipes or other material against the walls of the building
6. Store materials on shelves at least 8 inches off the ground and 12 inches away from walls

Step 2: Preventing Mice from Entering the Building

Preventing mice from getting into your building is call exclusion and is the most effective and permanent form of house mouse control. Before you try to trap or kill mice, you need to take the proper steps to keep them out. Otherwise, you'll be fighting a losing battle as new mice will replace the old ones. While this might seem like a lot of work, these measures will also help prevent other pests from invading the building as well as help to winterize. Since mice can squeeze through any opening larger that ¼ inch (about the size of a pencil) and are attracted to buildings when they detect heat escaping through these openings, the goal is to eliminate these openings.

1. Seal gaps around pipes with steel wool and caulk or mortar
2. Seal openings around vents and utility cables with caulk or cement
3. Close off any openings in your building's siding
4. Seal cracks and holes in the foundation with caulk, metal or concrete
  • a. Seal large openings with1/4 inch wire mesh
  • b. Do not use latex, plastic, boards less than ½ inch thick, plastic screening, vinyl or insulating foam to seal holes as mice can easily chew through them
  • c. Place steel wool or copper mesh inside holes before sealing to help prevent mice from chewing through.
5. Make sure that all doors, windows and screens fit tightly
6. If needed, cover the edges of doors and screens with sheet metal to prevent rodents from gnawing their way in
7. Make sure that any patching material is smoothly finished to prevent mice from pulling it out or chewing on it.

Snap Traps

There's an old saying about snap traps, "The early bird gets the worm, but the second mouse gets the cheese". While snap traps are considered less humane that live traps, they are more humane than poisons and glue traps and they are recommended by the CDC (Center for Disease Control). They are inexpensive and very effective when used correctly.

1. Set traps so that the trigger is sensitive and will release easily
2. Position traps so the trigger is next to the wall
3. When caught, dispose of mice quickly by placing them in a plastic bag then putting the bag in an outside container

How to Set and Bait a Trap

No matter what type of trap you use, it's important that you set and place them correctly, if you don't you'll probably be unsuccessful.

1. Set traps close to walls, behind objects and in dark corners where you believe mice have been active.
2. Make sure you use enough traps. Using too few traps is a common error.
3. Contrary to popular belief, cheese is not a good mouse bait, it becomes rancid too quickly
4. Good baits for mice include peanut butter, chocolate, dried fruit, bacon or a few drops of vanilla flavoring on a cotton ball. Regardless of the bait you use, make sure that it's securely attached to the trigger.
5. Mice tend to be curious of changes in their environment. If you don't catch any mice after two days, but you still find signs of mouse activity, relocate the traps.
6. After about t weeks, if you're not catching any more mice and there are no signs of activity, it's a pretty good bet the mice have been eliminated.


Getting rid of mice does not have to be a nightmare once you know how. Best of all, while it may take some time and energy in the beginning, many of the preventative steps taken will last for a long time and will help keep other pests from entering the building. For any questions contact the 23rd Civil Engineer Squadron Department of Entomology at 229-257-4397.