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The House Mouse

A Common Household Pest


The House Mouse

A Mouse Chewing Wiring in a Home

Jack Mann, Photodisc, Courtesy of Getty Images

A wily, curious creature, the house mouse is the most common of home-invading mice. Cute, perhaps, in a cage in the pet store, but not so cute when it decides to make your house its home.

A mouse in your house is, in fact, more than an just an unwanted pest, it can also be a health threat to all who live there.

Unfortunately, because mice are small, nocturnal, and nest in out-of-the-way places, you may not even know you have a problem until it is a major problem.

So, how do you know if you have mice? And why is it a health problem? The following provides a guide to common mouse identification, behavior, disease and damage, and signs.

Identification: What does the house mouse look like?

Small, with a slender body, its physical characteristics include:

  • Body length: 2 - 3 ¼ inches
  • Tail: 3 - 4 inches long and hairless
  • Weight: less than 1 ounce
  • Color: usually light brown to gray
  • Head: small with small black eyes, pointed snout and large ears

Behavior: What does it do?

  • Mice are nocturnal, meaning they are most active at night - when most of your household is asleep.
  • It is so flexible that it can get into your home through a crack or hole as small as 1/4-inch.
  • A mouse can jump as high as a foot, and climb 13 inches up smooth, vertical walls.
  • It can run 12 feet per second, and swim as far as 1/2 mile.
  • Being very inquisitive, a mouse will nibble or feed on any available human food, as well as other household items, such as paste, glue or soap.
  • It does not need free water, but can survive on the water in the food it eats.

Signs: How do I know if I have mice?

Although mice will rarely run in the open during the day (unless you have a major infestation), they do leave signs of their presence. Look for:

  • live or dead mice.
  • nests or piled nesting materials.
  • gnawed holes in stored foods, piled papers, insulation, etc.
  • food scraps or wrappings left behind.
  • excreted droppings - 1/4 - 1/8 inch with pointed end or ends.
  • rodent hairs.
  • runways - indicated by narrow pathways where dust and dirt has been swept clean, grease marks are noticeable, urine trails seen under black light.

You might also:

  • hear it skittering on hard wood or laminate floors.
  • smell the fetid odor of a large infestation.

Disease and Damage: Why are mice a problem?

According to the CDC:

"Worldwide, rats and mice spread over 35 diseases. These diseases can be spread to humans directly, through handling of rodents, through contact with rodent feces, urine, or saliva, or through rodent bites. Diseases carried by rodents can also be spread to humans indirectly, through ticks, mites or fleas that have fed on an infected rodent."

A few of these that can be carried or transmitted by mice are:

Mice are also a problem because they:

  • have no bladder control, so they trail urine wherever they walk.
  • leave behind 50-75 droppings each day.
  • can reproduce up to 35 young each year - from a single female.
  • cause structural damage through gnawing and nest building.
  • feed on and contaminate foods with urine, droppings and hair.
  • cause more than $1 billion in damage each year in the U.S.


Now that you know how tell if you have mice and the problems they can cause, learn how to rodent proof your home.

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