A single bat in the house does not always imply anything. However, multiple bats in your home are a sure sign of an infestation. The majority of bat colonies observed in homes are mother colonies. Each year, each mother bat gives birth to one youngster, while twins are occasionally born, and some few species give birth to more than once a year. So, by the time you see one, you could be living with them for years without knowing. Bats come to your house to escape from the rain.