Mice are prolific breeders: Indoors, mice breed year round. A female mouse can be sexually mature 1 1/2 months after birth, can produce 6 babies in each litter, and can have as many as 10 litters in a year. That’s 60 new mice just from one pregnant female. If you assume that half of her offspring are also females that will each be producing 10 litters, you can see what you’re up against.
Mice have extraordinary physical abilities: They can jump to the floor from a height of 8 feet. They can run up almost any vertical surface if it is rough. They have excellent balance. If they do fall, they land on their feet. They can climb and run along pipes, cables, and electrical lines. They can even travel for a considerable distance upside down. They can swim. They can adapt to almost any kind of environmental conditions, even surviving for generations in a frozen meat locker. Their small body size allows them to easily stow away and be transported to new sites. They can squeeze through a slot-like opening that is little more than 1/4 inch high. These capabilities allow mice to easily move into a building and then move from floor to floor. You can see why it’s hard to completely mouse-proof a building.
Mice are rarely restricted by food or water. Mice will feed on a wide variety of food, so they’re not limited by a particular food source. They don’t need very much food to survive.
A mouse eats an average of 1/10 ounce of dry food a day. Mice are nibblers, feeding 20 or more times a night at multiple sites. This feeding habit makes it difficult to kill them. When a water supply is not readily available, mice can survive from the moisture in their food.