10 Signs of a Mouse Infestation

Written by Chem-Wise on . Posted in Blog

Most people have a strong opinion on domestic mice. But whether you think mice as pets are cute or just creepy, you probably don’t want feral mice anywhere near your kitchen, drains, or basement.

Unfortunately, mice can infest even clean, well-kept homes in urban areas. Mouse infestations often appear out of basic necessity, when the rodents get low on food or have no other source of shelter. Because of these characteristics, most mouse infestations first appear in the fall or winter months when natural food sources become scarce and the temperature begins to fall.

Mice generally only come out at night to scavenge for food, so how do you detect their presence in your home, garage, or shed? Look for the following 10 signs of a significant infestation.

1. Bite Marks

Mice chew on the items that surround them in an effort to keep their continuously growing teeth short. If you have mice in your home, you may notice gnawing or bite markings on the following items:

  • Cables
  • Carpet and rugs
  • Paper goods
  • Piping
  • Wooden furniture

If bite marks only appear in a particular area of your home, chances are that the nest is close by.

2. Burrow Openings

While mice often use existing holes to enter buildings, they may also make their own. Mouse burrow holes typically appear in baseboards, corners, and foundations. You may need to look closely to spot a mouse hole, since many measure only ½ of an inch high.

3. Droppings

One of the most telltale signs of mice is droppings, as each mouse leaves behind approximately 80 droppings per day. Mouse droppings typically appear in crevices and under furniture. These droppings appear dark and rod-like in shape.

4. Live Mice

If you see a single mouse out in the garage, you needn’t assume the worst. However, if you notice live mice in a high-traffic area, you likely have a significant infestation. You may also notice dead mice under furnishings and along the baseboards.

5. Nests

Mice make nests to live in. Most indoor nests consist of fibrous material, like shredded cardboard or fabric, and measure around 5 inches across. You may find nests in any warm, undisturbed area, including storage boxes and crawl spaces.

6. Scavenged Food

Because mice typically invade homes looking for food, you will likely notice trails to or from your dry goods. Mice tend to gravitate toward the following food types:

  • Corn
  • Dry grains, including cereal
  • Oats, including oatmeal

However, mice will eat whatever food they come across. If you notice other infestation warning signs, check any food you have stored in the pantry for holes and scavenging.

7. Stains or Smears

Mouse fur contains strong oils that become smeared on surfaces that the mouse passes. If you have a big enough infestation, you may start to notice stains or dirty smears along your walls or baseboards. These smudges usually mean that one or more mice walk close to that surface on a regular basis.

8. Strong Animal Smells

Some infestations stay confined to the insides of walls or crawl spaces, but they still leave noticeable signs. One undeniable sign of a mouse infestation is the smell. Mice use urine to navigate unfamiliar spaces since they have poor eyesight. Unfortunately, this practice means that mouse nests and the surrounding areas often smell like ammonia. You may also begin to notice the smell of mouse feces during an infestation.

9. Unexplained Holes

In addition to practical burrows, mice tend to create other holes as well. Usually these holes come from a mouse’s need to keep its teeth short. Unexplained mouse holes may appear in any of the following:

  • Containers, especially cardboard boxes
  • Clothing
  • Upholstery

Even if you don’t see through-and-through holes, mice may leave behind shavings as they gnaw at items in your home.

10. Unusual Sounds

Because mice often live and travel through walls, you may hear them as they pass by, especially during the night. Mice communicate through squeaks, many of which are audible to humans. Additionally, you may hear the scratching of mouse nails clawing on your insulation, pipes, or wall interiors.


If you notice any combination of the signs listed above, contact your pest control service. Remember, mice reproduce quickly, so the sooner you take care of the issue, the better. Pinkies, or newly born mice, mature in as little as 20 days, and a single adult female can have up to 10 litters every year, so it’s in your best interest to act quickly.

A pest control professional can also give you recommendations specific to your property and location to help you avoid future infestations.

For more information on identifying pests, browse our ID Your Pest section. To learn more about common pests and pest control measures you should take, stay up to date with our blog.