9 Signs of Mice in Your House or Apartment

As temperatures start to cool down, mice and other pests living outside start seeking warmer places to nest for the winter. In urban areas like New York City, their best choice might just be your nice, heated house or apartment building.

Knowing if and when a mouse has found its way into your home is the first step in getting rid of it. Left unchecked, house mice reproduce quickly and may potentially cause all sorts of damage to your walls, building, electrical wiring, and personal belongings.

If you suspect that you have a mouse in your cozy townhouse or apartment, here are 9 signs of mice to look out for. Finding one or more of these signs together might mean it’s time to give your exterminator a call. 

9 Common Signs of Mice

  1. Droppings
  2. Scratching Noises
  3. Odor
  4. Gnawing
  5. Holes
  6. Runways
  7. Nests
  8. Urine Pillars
  9. Unusual Pet Behavior

#1 Droppings

  • Mouse droppings are generally 1/8 to 1/4 of an inch in length, resembling dark grains of rice with tapered ends. Fresh droppings are usually dark brown, and over time they may lighten in color.  
  • Droppings are often found where mice feed, such as in kitchen cabinets, pantries, and other areas where food is stored.
  • The amount of droppings that you find can be a good indicator of how serious the infestation is.

#2 Scratching Noises

  • Scratching noises at night might be from a mouse scurrying around your home in search of food or shelter.
  • As they travel about, you might hear these sounds coming from behind walls, in the ceiling, or across the floor.

#3 Odor

  • Mice emit a distinctive, musky smell that comes from the ammonia or urine.  Mice use this odor to help establish themselves and mark their territory.
  • This odor may be more noticeable in enclosed areas like pantries, drawers, and cabinets.
  • Mouse odors that become stronger over time might indicate a growing number of mice in your home. 
  • Unpleasant, rotting odors can also come from mice that have died.

#4 Gnaw Marks and Scratches

  • In order to file down their teeth, mice will chew on inedible materials like wood, plastic, cables, and electrical wiring.
  • Check for grooves and markings along baseboards and around cracks or holes in your walls.
  • Gnaw marks and scratches are usually small and clean cut, consisting of two parallel grooves that are 1 to 2 mm apart. 
  • If left alone, accumulated scratching and gnawing can lead to structural damage in your home.

#5 Holes

  • Mouse holes might appear as damaged sections of walls or paneling, a small gap or hollowed crack in the foundation, or space created by crumbling mortar. 
  • Check for holes under and behind kitchen cabinets, inside closets, around doors and floor vents, and where the floor and wall meet.
  • Mice can fit through holes as small as a dime, so it’s important to find and seal off any holes no matter the size.

#6 Runways

  • Mouse runways look like dirty or greasy smudges along floors and baseboards, created by their bodies and fur rubbing onto the surface.
  • Mice tend to follow the same path night after night, which creates these distinct tracks.
  • As you inspect your home, check walls and sidings with a flashlight to see any smudges or discoloration that might be tracks or rub marks from mice.

#7 Nests

  • Mice like to use soft household materials like fabric, shredded paper, and insulation to build nests.
  • Nests are typically located in dark spaces. For example, inside cabinets and drawers or behind drywall and large appliances.
  • Mice tend to nest near food sources, so you’re more likely to find them in pantries or cabinets where food is stored. 

#8 Urine Pillars

  • In a heavy mouse infestation, you might discover “urine pillars” — which are small mounds of grease, dust, dirt, and urine up to 4 cm high and 1 cm wide.
  • Urine pillars indicate that mice have been living and moving around in that space for some time.
  • These small mounds may be found in dark areas of your home like basements, attics, cabinets, and drawers.

#9 Unusual Pet Behaviors

  • If your pet hears or smells a mouse in your home, they might show unusual interest in that spot.
  • They might appear extremely alert, have a vocal reaction like barking, or scratch at spaces under refrigerators, stoves, or low-clearance furniture pieces.

Where to Check for Mice in Your Home

Mice are able to use their flexible skeletons to squeeze into very small spaces, so it can be helpful to know where to look for signs. If you suspect that a mouse has invaded your home or apartment, there are several common places to check.

Signs of Mice in Your Attic

Mice may tunnel through insulation in attic spaces and shred soft materials like cardboard, paper, and fabrics to use in their nests. Look in your attic space for chew marks on wood and listen for shuffling or scraping sounds.

Fill gaps and cracks in the exterior of your home to prevent mice from sneaking in and making their way into your attic.

Signs of Mice in Your Basement

Mice can gain entry to your basement through air vents and through cracks in the walls or foundation. Check for gnaw marks on cardboard, storage items, and wiring and look for potential nests in dark or dimly-lit corners.

To stop mice from coming into your basement, make sure there are no food or water sources near your home that might be attracting them. Examples include pet food, garbage, and scraps from your garden or fruit trees.  

Signs of Mice in Wall Cavities

Mice take advantage of dark, hidden spaces such as crawlspaces, suspended ceilings, and underneath stairs to get around without being noticed. They can get into these spaces through cracks and openings in walls and vents.

Listen for scratching or shuffling sounds and see if you notice any musty smells coming from vents.  Keep mice out of your walls by keeping those spaces dry and sealed off. 

How to Keep Mice Out

Here are some preventative steps you can take to keep mice out of your home. 

  • Reduce clutter
  • Vacuum regularly
  • Keep food sealed and stored properly
  • Don’t let garbage build up
  • Use trash cans with light-fitting lids
  • Seal cracks and crevices in walls
  • Fill large holes with steel wool or copper mesh
  • Install door sweeps
  • Cover ventilation ducts with wire screens

About MMPC

If you’re having trouble with mice in your house or apartment, MMPC can help. With 25+ years of eco-friendly pest management experience, our friendly and knowledgeable pest experts will help you find the right solution. Just give us a call at (212) 218-8218 or use our contact form to get in touch!