Mouse Infestation Signs: How to Know If Mice Have Moved In and What to Do About It

Finding out you might have a mouse infestation can be unsettling. Maybe you’ve noticed scratching noises at night, or tiny droppings in the pantry. Even if your house is spotless, mice can find their way inside in search of warmth, food, and shelter.

Understanding mouse infestation signs early helps you take control before things get out of hand. At Pure Pest + Lawn, we believe no one should have to live with the stress of wondering what’s scurrying behind their walls. This guide will help you spot the signs, understand why mice invade clean homes, and show how to keep them out for good.

What Are the Signs of a Mouse Infestation?

Spotting the first mouse might not mean you only have one. Mice reproduce quickly, and a small problem can become a full infestation in a matter of weeks.

Here are the most common mouse infestation signs to look for:

1. Droppings: Tiny, dark pellets about the size of a grain of rice, often found along walls, behind appliances, or inside cabinets.
   
   

2. Noises: Scratching, gnawing, or light running sounds in walls or ceilings, especially at night when mice are most active.
   
   

3. Gnaw marks: Mice chew constantly to keep their teeth short, so you might find marks on furniture, wiring, or baseboards.
   
   

4. Grease trails: Mice leave oily marks along the walls where they repeatedly travel.
   
   

5. Nesting materials: Shredded paper, insulation, or fabric tucked away in quiet corners.
   
   

6. Musky odor: A strong, musty smell in enclosed areas like pantries or basements can signal an active infestation.

If you’ve noticed any combination of these, it’s time to act fast. Mice can spread disease, contaminate food, and damage your home’s structure in a very short time.

For a deeper dive into the health risks mice bring, the Centers for Disease Control and Prevention (CDC) offers detailed information on diseases linked to rodent infestations (CDC Rodent Control).

My House Is Clean — Why Do I Have Mice?

This is one of the most common questions we hear, and we get it — discovering mice when you keep a clean home feels unfair. But here’s the truth: mice aren’t just attracted to dirt or crumbs; they’re attracted to opportunity.

Even spotless homes can offer:

• Warmth: Especially in colder months, homes provide ideal shelter.
  
  

• Food: Mice can sniff out even small amounts of pet food or pantry goods.
  
  

• Access points: Tiny gaps around pipes, vents, or foundations act like open doors.

Clean homes still create comfort for mice if there’s easy access to warmth and food. The National Pest Management Association notes that mice can fit through holes as small as a dime (NPMA PestWorld.org). That means even the best-kept home can become a mouse’s next nesting spot.

How to Find Entry Points for Mice

If you’re spotting signs of mice, identifying and sealing entry points is one of the most effective ways to stop them. Mice are incredible contortionists if they can get their head through an opening, their body will follow.

Here’s where to check for entry points:

• Around garage doors and foundations
  
  

• Near utility pipes, AC units, and dryer vents
  
  

• At window wells and door frames
  
  

• Under siding and roof eaves

Pro Tip: Go outside at night with a flashlight and look for gaps where light shines through from the inside. If you can see light, a mouse can fit.

Seal small holes with steel wool and caulk, mice can’t chew through metal fibers. For larger openings, use metal flashing or hardware cloth. Avoid foam-only solutions; mice can chew right through them.

For a detailed walkthrough, check out the University of Missouri Extension’s guide on Rodent-Proof Construction.

What Can a Mouse Chew Through?

The short answer: almost anything softer than metal.

Mice have strong, ever-growing teeth capable of chewing through:

• Plastic and rubber
  
  

• Soft wood and insulation
  
  

• Wires (a major fire risk)
  
  

• Cardboard and fabric
  
  

• Low-density foam or caulk

They can’t chew through steel wool, thick metal, or solid concrete. That’s why professional exclusion services, like the ones offered by Pure Pest + Lawn, rely on specialized materials to seal entry points permanently.

If you suspect mice have damaged wiring or insulation, it’s important to act fast, chewed wires can cause short circuits or even house fires.

How Many Mice Are in a Nest?

One of the biggest surprises for homeowners is how quickly mice reproduce.

A single female can give birth to 5 to 10 litters per year, each containing 5 to 12 babies. That means even one pregnant mouse can become dozens within months.

A typical mouse nest is built from shredded insulation, paper, or fabric and hidden in warm, quiet spots like attics, basements, or behind walls. Seeing one mouse often means there are many more nearby because if conditions are good enough for one, there’s probably a nest close by.

If you’re finding droppings or hearing noises at night, it’s time to schedule a professional inspection.

How to Stop Mice for Good

DIY traps can catch a few mice, but they rarely solve the problem. To truly eliminate an infestation, you need to remove every nest, every entry point, and every attractant.

Here’s the simple Pure Pest + Lawn plan:

1. Schedule a free inspection — We identify where mice are getting in and where they’re nesting.
   
   

2. Seal and treat — Our experts close off access points and apply safe, effective treatments.
   
   

3. Monitor and protect — We maintain ongoing protection with our Pure Protection Plan, ensuring mice stay gone.

When you work with our team, you don’t have to guess or worry you can feel confident your home is protected inside and out.