Mice are capable of getting in through almost any entranceway on your property from open wall vents to foundation gaps and weep vents to openings for cables or plumbing vents and they can make their openings by chewing through broken or damaged concrete foundations. Getting in through a window or an open back door is easier and getting in past a window-mounted air conditioner is just a matter of squeezing through a gap. For this reason, you must make sure the air conditioner is sealed on all sides. Using materials like cardboard or aluminum foil to seal it off is easy to chew through so make sure it’s sealed off with either the original plastic that it comes with or with plywood. Even then, they can still chew through it. The way mice enter homes is plentiful but if they want to make their hole they will need a place to hide. Tall grass, bushes and flowerbeds against the walls of the house are the best way for them to hide so make sure you don’t have any of those plants near the house. Mow your lawn nice and short so they have no way to hide while getting into the house. Keep doors closed and windows closed and if you want to keep them out get a professional to seal off anything they could enter. Including fixing any damaged foundation areas, sealing off weep vents with stainless steel vented inserts and seal of wall vents with fine mesh cages. This will dramatically reduce the chance of them getting inside the house.
Once a mouse gets in, and it is usually an already pregnant female they can breed and fill your home with mice incredibly fast. They can go from insemination to birth in just four weeks birthing a litter of up to fourteen babies at once. These babies then grow to adulthood in just two weeks and are ready to start mating themselves. Unlike humans, mice can breed with their siblings and produce few to none of the genetic issues humans have to deal with from inbreeding. The mice will grow from one to a hundred in a couple of months which is usually how long it takes to realize they are even there. This is why snap traps, capture traps and glue traps are all but useless in dealing with a mouse infestation. They have far too high a population and it keeps growing rapidly. Catching five mice a week is a waste of time as more and more will be born every day. They can repopulate their numbers so quickly that only a professional treatment using commercial-grade bait can get rid of them properly. This is because the bait can be fed on by all the mice in the house at the same time. It’s made to attract them by smell. They will ignore your food and feed on the bait which causes them to become dehydrated. This will result in them feeling sick. They will either leave the house to find water or die in their nest, desiccating entirely and losing all smell and moisture.
