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Keeping Mice Out of Your House

Keeping Mice at BayCooler weather has arrived, but with the cooler air also comes rodents. European house mice are gearing up for winter by searching for food and finding a place to keep warm.  Dr. Jim Armstrong, wildlife expert with Alabama Cooperative Extension System,  has some ideas on keeping mice at bay this fall.

Native mice, such as the cotton mouse and the white-footed mouse, are not normally a problem in homes. The European house mouse is what is most often found in homes. It is a non-native invasive species.

European house mice  look for shelter when the temperature begins to drop and food sources become scarce. Signs that your house has mice include chewing through food containers, such as potato chip bags or loaves of bread, small droppings about the size of a grain of rice, and chewed wood.

“Rodents have very strong jaw muscles, so they can easily chew through wood,” Armstrong said. “Its teeth are curved backward, which makes it hard to chew through a flat surface. However, they can readily chew through wood if they can get access to the edge of it.”

Most often, mice are found in cabinets, drawers or under the sink where the pipe goes through the wall. If the house has sanitation problems, it’s not uncommon to see mice at night on the counter or on the stove where there might be grease or food particles.

Keeping Mice Out

Armstrong explains that there are three steps to effective control of rodents: exclusion, sanitation and population reduction.


Mouse Exclusion - hardware cloth surrounded by spray foam. Photo Credit: Dr. Jim Armstrong

Mouse Exclusion – hardware cloth surrounded by spray foam. Photo Credit: Dr. Jim Armstrong

“Mice can fit through a quarter inch opening,” Armstrong said. “So trying to exclude them can be difficult.”

Armstrong advises to look for areas that mice can get access and block those areas using a spray foam insulation and hardware cloth.

Spray foam insulation is an expanding foam that is good for blocking holes. However, mice can chew through it easily. To make it stronger, it can be coupled with quarter-inch thick mesh hardware cloth, which mice are not able to chew through, with spray foam surrounding it.

Armstrong explains a common place for mice to enter is under the sink because the sink pipe does not always have a good cut around it. He advises to pack it with steel wool and surround it with spray foam.

“One thing that I do is take a piece of hardware cloth, and roll it up tight so it’s like a tube of solid wire,” he said. “I’ll pound one side of it in so it’s small, and I’ll put it in the hole with a board against it and drive it in to the hole where it won’t come out. You want to get it wedged in there as tightly as possible.”


It’s important to remember that finding a mouse in your home does not always indicate a sanitation problem. However, if the problem persists, it could be an issue with cleanliness.

“Long term populations are probably a sign of a sanitation issue, but just having a couple of mice does not mean you’re a filthy person,” said Armstrong.

Armstrong suggests that if mice are getting into food, put the food into some kind of plastic container. Mice can get into those, but they generally won’t unless they’re in a real food shortage.

Population Reduction

Mouse Trap – Photo Credit: commons.wikimedia.org

Population reduction can be done through a combination of rodenticides, such as rat poisons or trapping. For a small problem, Armstrong recommends setting mouse traps baited with peanut butter in the cabinet. However, since mice are so light and agile, they are sometimes able to lick the peanut butter off without springing the trap.

“If you start getting the mousetrap out and it’s not sprung, but the bait is gone, try setting it so that it fires more easily or put your bait where the mice have to work a little harder to get it,” he said.

Armstrong explains that you must first make sure that it’s mice that are causing the problem because a trap wouldn’t phase a rat or squirrel. Sometimes, you have to test out different things before finding what works.

Exclusion, sanitation and population reduction are the three steps, and each is necessary to solving the problem of mice in your home.

“Very seldom will one thing alone solve the problem,” Armstrong said.  “You can trap mice, but if you don’t do something to control that they’re getting in, it’s going to be an ongoing problem. Trapping the ones that are in there has to be coupled with blocking the entrance and removing access to the food source.”

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  1. wow nice article thx

  2. People don’t realize how small of spaces that mice can squeeze their little bodies into. Even spaces like wires, cracks and beams. Almost any home could be a victim of mice!