Mice are one the nastiest pests you can encounter, as they cause structural damage, multiply quickly, and carry diseases. Mice are also relatively clever, sneaky critters adept at hiding from humans. To make matters worse, by the time you spot a single mouse scurrying about, it’s likely not alone or won’t be for long. Thankfully, when mice take up residence, they leave a few telltale signs that they’re around, especially if they have started making nests.


One of the most common signs of mice is their droppings. Mice eat a lot and, as a result, leave a lot of feces. Mouse droppings resemble a small, black grain of rice. They are about a quarter of an inch long and often confused for cockroach droppings. These droppings are most commonly found around food sources, along rodent runways, in breeding areas, or in nesting areas like the attic or basement. Droppings often contain dangerous diseases, so when cleaning them, be sure to:

  • Wear vinyl or latex gloves.
  • Use a respirator or dust mask.
  • Never stir them up by sweeping or vacuuming. 
  • Disinfect the droppings with a combination of bleach and water before removing them. 
  • Remove with a paper towel and dispose of in the garbage. 
  • Thoroughly clean and disinfect the entire area with antibacterial cleaner. 

Strong Smell 

Mouse infestations create a powerful, musky smell that resembles ammonia and comes from the mouse’s urine. This smell can become highly noticeable in enclosed areas, like cabinets, between walls, or closets. This smell can be faint at first, making it difficult for you to detect early on. Household pets usually pick up on this scent, so if you notice your cat or dog giving a specific area a lot of attention, it could be due to it detecting the smell of mice. The scent may also be detectable along paths mice frequently travel, usually along baseboards, rodent runways, or behind appliances. 


Mice are nocturnal creatures, coming out of their favorite hiding places in the dead of night to scrounge for food, reproduce, and dig out new habitats. These hidden spaces are dark, enclosed nooks with access to soft nesting material. Places like the attic, basement, or between walls are prime real estate for mice. Mice will use joists in your walls to move between nests and other sections of the wall or feeding locations. They will make audible scratching noises and occasional squeaking sounds as they travel, burrow, and hop between your wall structures. While it can be difficult for you to notice these noises at first, pets can once again spot these signs early; so if your dog or cat is more active at night and investigating a specific wall, it might indicate a mouse problem. 

Missing or Damage Food

Mice eat a lot, making up to 30 trips to a food source per day. Mice enjoy grains, fruits, seeds, and any food rich in fats, oils, sugars, and carbohydrates. For a mouse, our pantry is a buffet stocked to the brim with all their favorite foods. They are also messy eaters, having to chew through packaging and containers to get to their meals. So if you find small holes at the corners or sides of your cereal, dried food, or dry mix boxes, a mouse has been chowing down. Be sure to throw away all food a mouse has gotten into, as mice harbor many dangerous diseases

Urine Pillars

When an infestation has gone untreated for a while, you will begin to see “urine pillars.” These foul-smelling mounds are a combination of grease, dirt, hair, and urine. There may also be urine trails leading to and from these mounds. Urine pillars are often found in rodent runways, in locations mice frequently eat, and within the immediate vicinity of their nest. 

Teeth Marks 

Infestations of mice are not only a health concern but also a dangerous fire hazard. Mice need to continuously gnaw on hard, inedible material to wear down their ever-growing teeth. Homeowners plagued with mice will find gnaw marks on furniture, tools, sections of walls, and food containers. Unfortunately, mice are prone to chewing through wires and other electrical devices, resulting in outages, shorts, and fires.

Grease Marks

When mice repeatedly pass through the same area, referred to as a rodent runway, they will leave small grease marks. These marks are made from the natural grease of their skin and fur combined with dirt. This grease rubs off on the ground and baseboards of your home as they pass through. Grease marks can be found alongside tracks and droppings inside runways, indicating an infestation. If you have difficulty spotting them, a black light will make the streaks and track marks visible. 


When homeowners find a rodent nest, they are likely already aware of the infestation. However, this is not always the case, and mice can create nests in surprising places. Rodents choose locations that are secluded, cramped, dark, and situated nearby food and nesting material for their homes. Mice utilize shredded paper, cotton stuffing, cloth scraps, and other soft materials to line their nests. The most common locations for nests are attics, basements, crawl spaces, under floorboards, within suspended ceilings, or in the space between walls, but mice will also create nests behind large appliances like fridges and stoves. 

Living or Dead Mice

Seeing a mouse scurry by, especially during the day, is a powerful sign of a large infestation. Since mice are most active at night, the colony has become sizable if they take action during the day. Likewise, discovering a dead mouse or multiple dead mice is another substantial sign of an infestation.

How to Prevent Mice

Keeping mice out of your home comes down to good home maintenance and proper pest control practices

Step 1: You need to remove the reasons for mice to enter your home in the first place. This means cleaning up piles of trash or debris from your lawn, keeping outside storage spaces like sheds free of clutter, and keeping all compost in sealable bins. 

Step 2: Remove access points that a mouse can take advantage of by sealing cracks and openings in your walls, siding, and foundation. Patching holes in window screens that lead to your basement and crawl space also helps. 

Step 3: Finally, you have to make the inside of your home unappealing to mice. Do this by not leaving food out, cleaning up trash, and keeping all loose food in sealable plastic containers. 

Final Thoughts

While domesticated and bred mice can be fantastic pets, an infestation of mice is nothing but a problem for homeowners. Mice create unsanitary conditions by contaminating food stores with dangerous diseases like hantavirus, salmonella, and lymphocytic choriomeningitis. Mice also destroy property and can damage structures of a home with their constant gnawing. Even worse, mice are a dangerous fire hazard, as they frequently chew through electrical wires. 

You should always be on the lookout for any telltale signs of rodent infestations, primarily through spotting droppings and grease marks and listening for these scurrying pests in walls. If a mouse infestation has become too much for you to handle, your best recourse is to contact a pest control company to eliminate them.

Editorial Contributors
Sam Wasson

Sam Wasson

Staff Writer

Sam Wasson graduated from the University of Utah with a degree in Film and Media Arts with an Emphasis in Entertainment Arts and Engineering. Sam brings over four years of content writing and media production experience to the Today’s Homeowner content team. He specializes in the pest control, landscaping, and moving categories. Sam aims to answer homeowners’ difficult questions by providing well-researched, accurate, transparent, and entertaining content to Today’s Homeowner readers.

Learn More

Lora Novak

Senior Editor

Lora Novak meticulously proofreads and edits all commercial content for Today’s Homeowner to guarantee that it contains the most up-to-date information. Lora brings over 12 years of writing, editing, and digital marketing expertise. She’s worked on thousands of articles related to heating, air conditioning, ventilation, roofing, plumbing, lawn/garden, pest control, insurance, and other general homeownership topics.

Learn More