Signs of Mice Infestation in the House

Finding out that you have a mouse infestation in your home can be unsettling. By recognising mice presence early, you can prevent a full-blown rodent infestation. The first step in stopping mice is to identify early signs of infestation.

We will cover the key signs to look for and what to do if you suspect mice presence in your home.

What Are The Signs of a Mouse Infestation?

When in doubt of a mice infestation, you have to look for other indications. We have prepared a list for you with all the signs you have to pay attention to and how to recognise which is which.

• Mouse droppings – Mouse poop is a sure sign that you have a mice infestation. There could be from 50 to 80 mouse droppings a night. They are small, dark in colour, and glossy with moisture. They become dry and grey within a few hours. Each dropping around 3-5 mm in diameter. The most likely places to find mouse droppings are near food packages, in drawers or cupboards, under sinks, and along rodent runways. You will find the highest number of mouse poop where the rodents are nesting or feeding.
• Mouse urine puddles – Mice urinate a lot and just like the droppings, you are more likely to find small puddles closer to their nest.
• Mouse urine pillars – Where infestations have become bad, grease, dirt, and hair can combine with mouse urine to create what is known as urine pillars. These small mounds indicate that mice have been active for some time.
• Mouse urine smell – What does mouse pee smell like? Mice urine has a strong ammonia-like smell. This smell can linger for a long time (even after an infestation has been removed). Mouse urine will usually mix with dust and grime to form dry crusty yellowish marks that emit an ammonia-like smell. The look of mouse urine stains will vary depending on the surface. For example, if they urinated on a clean white cloth, you will easily see small yellow stains.
• Mouse smell – A strong, musty odour is another common sign of a mouse infestation. Mice have a distinct scent, and if you notice an unpleasant smell, especially around food areas, walls, or hidden corners of the house, it could be a sign of mice nesting nearby. Over time, the smell may intensify if the infestation continues, as accumulated droppings and urine contribute to the odour. This smell is a mixture of mouse pee, droppings and ammonia. The stronger the smell is, the closer you are to a nest.
• Mice tracks – In areas of your home that are less frequently used, such as attics, basements, or closets, you might notice mouse tracks or footprints in dust or dirt. Mice tend to travel along the same pathways repeatedly, leaving behind a trail of small, visible marks in dusty or dirty areas. This is a subtle sign of their movement, indicating that they are active in that area.
• Gnaw marks and chewed materials – Mice have a constant need to gnaw in order to keep their teeth trimmed. Therefore, chewed marks on food packaging, furniture, wires, insulation, and even wooden beams can indicate a mouse presence. These gnaw marks are particularly common in areas such as the kitchen, pantry, or attic, where mice can access food or materials to chew on. If you notice exposed wires with bite marks, it is especially concerning, as this can be a fire hazard. Mice can cause significant damage to your home’s electrical system and plumbing by chewing through wires and insulation.
• Scratching noises and squeaks – During the night, mice are very active and most of their adventures, when scavenging, occur while we are sound asleep. Listen for different noises like scratching and steps coming from inside the walls, around cabinets, lofts, attics and false ceilings.
• Mice nests – Finding a nest is a sure way to determine if you have an infestation at hand. If the mice have already gotten to the point of having an organised, structured nest, then surely their number is not low and your home is also their home. Always be on the lookout for potential nesting locations, such as cabinets, the inside of walls, behind electrical appliances and suspended ceilings.
• Mouse sightings – Saw a mouse during the day? If you do happen to see a mouse in broad daylight, then, probably the infestation is already getting out of control and you will need the help of an exterminator.
• Nighttime activity – Mice are nocturnal creatures, so they are most likely to be active and come out of their hiding during the night. They go out searching for food and nesting material when everyone is sound asleep.
• Rub marks – As mice follow the same routes along walls, they leave behind greasy or dark streaks due to the oils and dirt in their fur.

Where Do Mice Hide in a House?

If you have doubts about a mouse infestation on your property, following the signs above, you will be able to determine whether there is one or not. It’s really important as well to understand which are the most likely mice nesting locations. The rodents use their very bendable skeletons to squeeze into very tiny spaces, so when you are on the lookout for a mouse, be sure to check out these places.

• Lofts, attics & eaves – Most of the material that mice use for nesting is hidden in your loft or attic, probably stuff that you’ve stored away for winter or summertime, depending on the season. Every box, piece of fabric and loft insulation is a perfect building material. Check if they are chewed, gnawed and damaged and always try to scent the ammonia smell of their urine.
• Kitchen cupboards and electrical appliances – One of their favourite place for nesting is in your kitchen, as they’ll try to be as close to the food as they could. The lower cupboards are very often their prime choice, so be sure to check all of them. Unfortunately, the pests usually manage to cram themselves behind your electrical appliances and chew all the cables, again, searching for nesting material. It’s really important to check all of them, mostly for your safety.
• Basement and cellars – Similar to the attics, mice will find an entry point to your basement or cellar without breaking a sweat. A broken vent or air brick is more than convenient for their tiny bodies to go through.
• Cavity walls – Any space that is tiny, dark and hidden is a perfect place for a house mouse to settle in. Suspended ceilings, under the stairs, crawl spaces and airing cupboards very often go unnoticed and mice manage to build their nest and colony with no problem. You can find more info about what to do when you have mice in your walls below.

How do Mice Get in the House?

There are lots of different ways a mouse can enter one’s property. They are extremely flexible and can squeeze their tiny bodies through very small holes. Mice will use every small opening that they come across like under doors, around utility lines, through vents and more.

They might not run a lot but they are amazing jumpers with their jumps being as high as 45 cm. Mice also climb vertically up to 2 meters and can walk along very thin ropes and wires. Considering the fact that they can even enter through your toilet, almost everything is an entry point for them.

What to do if You Have Mice in Your Walls

If you can hear tiny steps, screeches and scratches, you probably have mice in your walls. You can take care of them by placing a food-scented snap trap along the bottom edges of the wall. It’s important to get them out and get rid of them after that, instead of placing poison and leaving them to die somewhere in the walls.

Another way to attract mice to get out of your walls is to drill a small hole the size of a coin in the place you think they are most active. Drill the same hole on the side of a cardboard box and place the latter, so it’s adjacent to the wall. Put some food in there, like peanut butter, for example, so you can tempt the vermin to get out of their hiding place. It would be better if you can see when you have caught a mouse, so to be able to do this, you have to remove the top part of the box and replace it with transparent cellophane. You should have your first mouse in the next hour!

After you have lured all the mice out of the walls, make sure to block all entries to your house, from inside and outside, as well. You can use mesh wire and plasterboards to seal the holes you need to.

Are There Mice in my Garden?

To determine whether you have mice outside your house, you have to check the following locations:

• Sheds – Sheds are basically like mini-houses and are very often a place where we may store pet food, bird food or keep other stuff that is attractive to the rodents. Mice can find whatever they need for their nests and well-being in a shed, so check the space thoroughly.
• Garages – One of the places mice love to make nests are the engines of our cars, so make sure you check them for signs of nesting. In any case, the garage is a very good place for the mice to prosper with its many hiding places and nesting materials.
• Compost bins – They are perfect for mice as they are comfy, full of food and hidden. Check your bins for gnaw marks and scratches on the lids.
• Vegetation – Overgrown plants make a very good shelter for mice as they provide food and nesting materials at the same time. Also, they are in places people rarely check for infestation and so the pest problem often goes unnoticed.

How to detect a mouse infestation

To confirm that there is an infestation on your property, you have to look out for all the signs mentioned above at all possible locations. Even though the best way to decide if there is an infestation or not is to actually hire a pest control technician, who knows what to look for, you can make a couple of simple tests on your own:

1. The flour test: pour flour on the most used mice routes and check how many tiny steps you can distinguish. The prints don’t actually look like prints, but more like dots, spread out on the floor. They are around 0.5cm long and very close to each other.
2. The biscuit test: mice will never refuse an easy snack, so just leave a cookie outside for the night. In the morning, check if the biscuit is still in one piece. You can also use this method to determine whether you have mice or rats. Mice will only gnaw on the cookie until they are full and leave after. Rats will take it with them, to store for the winter.

How many mice indicates an infestation?

An infestation is defined by the level of activity, reproduction, and spread within a property, not just the presence of a mouse. One mouse may be a scout searching for food or shelter. However, mice are social creatures, so seeing one often means more are nearby.

If you spot multiple mice over a short period, it suggests they have established a nesting site. Mice reproduce quickly, meaning a small problem can escalate rapidly. Each mouse needs around 2 weeks to reach reproductive age and will continue giving birth at the same speed. Even if by any chance you have only one mouse that has got lost and is not a part of a nest, it’s still a problem. Seeing a single mouse does not always confirm an infestation, but it should not be ignored!

What Are The Dangers of a Mouse Infestation?

Even if their adorable looks may deceive a lot of people, everyone needs to be aware of the danger mice present to our family, pets and home.

• Damage to the property and your personal belongings – Mice will go everywhere they can in order to gather material for their nests. They gnaw on furniture, dig holes, chew your clothes, etc. These rodents can make a house out of everything, so in two words – nothing is safe. And when they’re done making their nests, they’ll continue destroying your home, because their long teeth need to be frequently filed down.
• Risk of fires – Included in everything else that mice chew, we have electrical wires, as well, which, if damaged, increases significantly the danger of a house fire.
• Contamination of your food supplies – The main route of a mouse includes going through your kitchen cabinets, fridge insides and other food sources. They spread diseases and contamination to everything they get in contact with even if it looks untouched.
• Bringing in more pest species with them – Mice often travel with a company from house to house. They bring fleas, ticks, lice and other mites to your property and all the diseases that come with them.
• Diseases – Mice are frequent hosts of various parasites and can even induce asthma and allergic reactions in people.

What attracts mice to your home

It’s important to know everything that could attract mice to your property, so you can prevent an infestation in time.

• Food and shelter – Mice are understandably attracted to the warmth and security our human houses provide. They also very much enjoy all the food that we leave out during the night. Very often it’s not even our food that they go after but our pet’s food, which is almost always left out in the open. They will take every small food particle that is left outside as they don’t really need much to get fed.
• Overgrown lawns and unkept vegetable gardens – The perfect conditions for a mouse to have a nest will be under the comfort of the leaves in your garden, between the compost and the unmowed grass. They are hidden, secure places, which are also only metres away from any food sources. And the food is almost anything – from fruits and vegetables, too young to be harvested, to rotting pieces, full of worms.

Read more: How to keep field mice away from your garden.

How long does a mouse infestation last?

An infestation of mice can last for quite some time, depending on the severity, the availability of food and shelter, and the speed at which control measures are implemented.

Mice breed rapidly, with a single female producing up to 10 litters per year, each containing 3–14 pups. Without intervention, an infestation can persist indefinitely and grow exponentially. If a house provides abundant food sources and nesting areas, mice will continue to thrive. A lack of food or shelter can naturally limit the infestation, but complete eradication requires proactive action.

A mouse infestation can last for months or even years, as mice continuously reproduce and spread. Using mouse traps, poison, and sealing entry points can reduce the rodent population, but it may take several weeks to months to fully eliminate an infestation. A severe mice infestation can often be brought under control within a few weeks, but complete extermination and prevention may take longer.

Final thoughts

Recognising the signs of a mouse infestation early can save you a lot of time, effort, and money. From droppings and gnaw marks to scratching sounds and nests, being vigilant about the presence of mice in your home is crucial. If you notice any of these signs, take immediate action to address the issue before it escalates.

By ensuring your home is properly sealed, eliminating food sources, and using effective control methods, you can successfully prevent a mouse infestation and protect your property from damage.