Unless you have a pet mouse or rat in a cage, any wild rodent in your home is cause for concern. In addition to startling you with unexpected sightings, rodents such as mice and rats can contaminate food, chew up important papers, damage electrical wiring, and spread disease.
It can be quite difficult to completely eradicate rats or mice that have infiltrated your home and established hidden nesting areas, so it's best to prevent infestations before they can happen. When you do find your home playing host to mice, rats, or other unwanted rodents, take whatever measures necessary to remove those pests and block their entry points into your home.
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Signs of Rodent Presence
When a mouse or rat decides to visit, it often goes unseen—at least at the start. Usually, signs that rats or mice are present include small dark droppings of feces that look like tiny grains of rice and are found along walls or in places where food materials are present. You may also notice other destruction, such as chewed holes in boxes and bags of dry goods in a pantry, in pet food bags, or in bags of grass seed in the garage.
Close inspection along baseboards or near any holes in the floors, such as where radiator pipes come through, may show rub marks or gnawed areas where the rodents have chewed to gain access. In hidden areas beneath cabinets, you may find small nest areas filled with shredded paper or wood shavings.
If you have pets, your dog or cat may exhibit alert behavior, sensing the presence of a rodent. And you may even hear sounds of scurrying or scratching in the walls or floors, especially at night when the house is silent and dark.
Learn how to keep mice out of the house with these mostly poison-free practices.
11 Ways to Keep Mice Out of the House
Block All Entry Points
The single most important preventive measure you can take to keep mice and rats away is to inspect the foundation and walls of your house to make sure any potential entry points are blocked. The fall season, when rodents seek to get in from the cold, is an especially good time to run your inspection tour. Mice can enter by squeezing their way through cracks as small as 1/4-inch in diameter, so block foundation cracks with a masonry repair material, and inspect joints around windows and door sills for cracks that might allow rodents to enter.
Make sure weather seals along the bottom edges of garage doors are in good shape. If your garage is insulated, it may become a cozy home for a rodent. Check your attic, as well, since rodents love the warmth of insulation. However, there's no completely effective rodent-proof insulation on the market as of yet, although spray foam insulation may help keep rodents at bay.
Move Bird Feeders Far From the House
The seeds and ground grains that go into most bird-food mixtures are a delightful treat for rodents, as evidenced by the presence of squirrels (larger cousins to rats) that frolic around any bird feeder. Feeding birds is an admirable hobby, but you shouldn't be surprised when mice and rats are drawn to the ground around your feeders. If you must feed birds, keep your feeders as far from the house as possible.
Seal Pet Food
Transfer dog and cat foods to sealed, airtight storage containers immediately after buying them. More than one homeowner pouring a bowl of dog food has dumped out a squeaking mouse at the same time. Dry pet foods are mana from heaven for rodents, so store them in tightly sealed containers well above the floor.
Seal Garbage Bins
Garbage cans and bins kept alongside the house or garage will be a siren call to rats and mice (and maybe bigger pests, such as raccoons or stray dogs and cats) unless they are kept tightly sealed with airproof lids. If possible, keep these utility containers as far from your house as you can, put them on platforms above the ground, and as an added prevention, secure lids with bungee cords or heavy rocks.
Control Foundation Plantings
Dense shrubs and garden planting that butt up close to the house provide hiding spots for mice and rats (and termites) as they seek entry holes through foundations or walls. Shrubs along the house should be planted a few feet away from the foundation, and make sure to keep the soil level low enough that mice cannot squeeze their way up behind the siding.
Seal Dry Foods
Flour, sugar, and other food kept in bags or paper cartons are easily broached by rodents and bugs, such as weevils. Instead, keep these foods in tightly sealed plastic or metal containers on high shelves or in the refrigerator. Rodents will have no incentive to take up residence in your house if they don't smell any source of food.
Clean Floors and Countertops
Casual, messy housekeeping that leaves spilled crumbs or food scraps on floors or countertops is an invitation for mice and rats. Always have a handy sweeper to capture crumbs and never leave uneaten bowls of pet food in dishes on the floor. If you have a pet bird, sweep up scattered seeds that have fallen on the floor under the cage.
Keep Outside Doors Closed
Garage doors left wide open can be an invitation to rats and mice, especially in the fall when these rodents are seeking a warm place for winter. Get into the habit of closing your garage door immediately after entering or exiting with your car, and also keep side entry doors to the garage closed. Keep sliding patio doors and basement windows closed, or at least protected with screens, to prevent rodents from entering. Never leave a garage door, or other entries open overnight, as the dark hours are when rodents are especially active.
Set Traps and Bait
Mostly as a diagnostic measure throughout the year, set a few traps and bait stations indoors. A live trap is a humane and poison-free way to trap and release rodents while alerting you when they are finding entry into your home. The best live traps are chamber-type devices with a spring-loaded door that snaps shut when the mice enter in search of food. Avoid sticky trap designs, since mice have been known to chew their own feet in an effort to free themselves from the adhesive—these traps are by no means humane.
If you have no qualms about killing mice, then traditional spring traps are a good choice; they usually kill mice very quickly and without much pain to the creature.
A bait station contains poison. It is much easier to catch one or two mice or rats at the start of an infestation than to deal with it after a whole colony has set up a home in your walls. Put any type of trap or rodent poison baits completely out of reach of children and pets.
If you must use poison baits, never set them outdoors, since squirrels and pets can find and eat them. Rodent poisons are a major cause of pet poisoning in the U.S. Plus, indoor mice that are killed by poisons may die in the walls, leaving you with the issue of their decaying remains.
Use Holistic Repellants
In one study, eucalyptus oil showed some success in repelling rats. But percent repellency was more when the oil was applied daily and alternatively as compared to when applied once a week indicating low persistence of the repellent effect due to volatile nature of the oil.
Adopt an Animal Predator
A pet that loves to hunt prey, or even an owl nesting outdoors in your garden, can be excellent rodent control. But because pet food is always present in a house with pets, rodents may find your home to be a good source of food.
However, a young, aggressive cat, or a dog species such as a terrier with a reputation for hunting small animals, can often catch rodents before they can take up housekeeping and form nests to reproduce.
What Causes Mice in the House?
Mice are drawn into residential homes because these good locations for plenty of food and dark sheltered areas to nest and reproduce. Your home is also a source of warmth during colder times of the year. The typical home is an ideal environment for the common house mouse.
How to Prevent Mice in the House
As outlined above, preventing mice from entering your home is largely a matter of denying them entry points and eliminating the sources of food they depend on.
Mice vs. Rats
Although these rodents are similar in appearance, rats (Rattus spp.) are considerably larger than mice (Mus musculus and other species). Mice can grow to about 8 inches long, including the tail, while rats can grow to as much as 19 inches, including the tail. Mice have sparse hair on the ears, a pointed snout, and are typically light gray-brown or black in color with white or buff underneath. Rats have hairless ears, blunter snouts, and are typically a darker gray in color. Rats are a more secretive creature, likely to hide in walls, while it's common to see mice curiously exploring.
Both rats and mice can start fires by gnawing on electric cables.
Do mice carry diseases?
The CDC reports an impressive number of diseases that can be carried or spread by rodents, including mice: hantavirus pulmonary syndrome, hemorrhagic fever, lassa fever, leptospirosis, lymphocytic chorio-meningitis (LCM), Omsk hemorrhagic fever, plague, rat-bite fever, salmonellosis, and hantavirus.
How long do mice live?
On average, house mice live 9 to 18 months. But mice mature and reproduce so fast that a single breeding pair may create a perpetuating colony that will remain until you trap or otherwise eliminate all of them.
What should I do with live trapped mice?
Homeowners who prefer live traps are left with figuring out what to do with the live mice.
The best method is to put the live trap into a heavy plastic bag and take it to a park or field at least 2 miles from your home before releasing the mouse. But be aware that house mice (Mus musculus) released outdoors will quickly seek indoor shelter again—if they are not snatched up quickly by owls, hawks, foxes, prowling house cats, or other predators. Thus, it is debatable if live-trapping is indeed more humane than kill traps. And your neighbors may have something to say about your practice of releasing live mice into the neighborhood.
What should I do with dead mice?
Mice killed in traps or with poison bait should be placed in a sealed plastic bag and disposed of in household trash. Wear disposable gloves to handle them. Don't flush them down the toilet, add them to a compost heap, or allow cats or other pets to eat them. Avoid touching dead mice if you can; wash your hands thoroughly if handling is unavoidable.
Morand, S., et al. Rodents as Hosts of Infectious Diseases: Biological and Ecological Characteristics. Vector-Borne and Zoonotic Diseases, vol. 15, no. 1, Jan. 2015, pp. 1–2. liebertpub.com (Atypon), doi:10.1089/vbz.2015.15.1.intro
Is There A Mouse In The House? Eliminate Mice With IPM. Penn State Extension,
Singla, Neena, et al. Potential of Eucalyptus Oil as Repellent against House Rat, Rattus Rattus. The Scientific World Journal, vol. 2014, 2014, pp. 1–7. doi:10.1155/2014/249284
Centers for Disease Control and Prevention. Diseases directly transmitted by rodents. Updated July 5, 2017