Mice in the House | Signs, Droppings and What to Do

Mice are easy to miss. They’re small, quiet and mostly out at night, so the first sign is usually something they left behind: droppings in a drawer, a nibbled corner on a bag of rice, or a soft scratching sound near the floor. Here’s how to read those signs, tell mice from rats, and handle it before a few mice turn into many.

Signs of Mice in the House, Room by Room

Mice in the kitchen

• Droppings in silverware drawers, along the backsplash or under the sink
• Tiny chew holes in boxes and bags in the back of cabinets
• Crumbs or shredded paper behind the stove or fridge

Mice in the pantry

• Small holes in cereal, rice, pasta, flour or pet food bags
• Droppings on shelves, especially near the floor
• A stale, musky smell when you open the door

Mice in the garage

• Chewed birdseed or pet food bags
• Shredded cardboard, paper or fabric in storage bins
• Droppings along the walls and near the garage door corners

Mice in the walls and ceiling

• Light, quick scratching, often low in the wall or near the floor
• Sounds that move along the wall at night
• Pets staring at one spot near the baseboard

Mice vs. Rats: A Quick Check

Not sure which one you have? Mouse droppings are about the size of a grain of rice; rat droppings are about half an inch or longer. Mice usually show up low, in kitchens, pantries and garages, while roof rats tend to stay up high in the attic. Mice can squeeze through a gap about a quarter inch wide, while a rat needs about twice that.

If what you’re hearing is heavier running overhead, our Rats in the Attic guide is the better place to start.

How Mice Get Into the House

A mouse can fit through a gap about a quarter inch wide, roughly the width of a pencil. In Mission Viejo homes, the usual spots are:

• Garage door corners and worn bottom seals, one of the most common ways in
• Gaps around pipes under the kitchen and bathroom sinks
• AC line and cable openings where they enter the wall
• Dryer vents without a working flap
• Gaps along the base of stucco walls, including near the weep screed
• Side and back doors with no door sweep

Once inside the garage, mice often follow pipes and wiring into the kitchen and walls.

What to Do Tonight

1. Seal up food. Move cereal, grains, snacks and pet food into hard plastic or glass containers with tight lids.
2. Clean the counters and floors so there are no crumbs left out overnight.
3. Bring pet bowls in or empty them before bed.
4. Throw out anything chewed. Toss open packages mice could have reached.
5. Note where you find signs. Which drawers, which shelves and which walls help pinpoint the nest.
6. Clean droppings the safe way. Air out the space, wear gloves, spray droppings with disinfectant, let it soak, then wipe them up with paper towels.

What to Avoid

• Don’t sweep or vacuum droppings dry. It can stir germs into the air.
• Don’t plug every hole right away. Sealing mice inside can push them deeper into walls and cabinets, where they may die and leave a smell. Find out where they’re living first.
• Don’t use loose poison bait. Most anticoagulant baits are restricted in California, and bait near food, kids or pets isn’t safe. See Is Rat Poison Legal in California?
• Skip glue boards and ultrasonic plug-ins. University of California pest experts don’t recommend glue boards for home use and don’t consider ultrasonic devices effective.
• Don’t count on the cat. A cat might catch a mouse or two, but it won’t find the nest or close the gap.

When to Call for Help

A single mouse caught on day one might be the end of it. Call for an inspection if:

• You keep finding fresh droppings after a few days
• You see mice during the day, which often means there are many
• Signs show up in more than one room
• You hear scratching inside the walls or ceiling
• You can’t find where they’re getting in

Our Mouse Control page explains how we find the nest, trap the mice and seal the gaps.