In small numbers, bats aren't much of a problem. It's when the colony grows in size that real problems start to occur, and they mostly have to do with guano buildup. However, even if you only have a small colony, it's best to deal with it as soon as possible. Bats live a very long time, and they stay in the same place basically forever (thousands of years, conditions permitting). The colony grows larger every year, as the female bats have babies each summer, and those babies join the colony. After a period of years, you can have thousands of bats, and that's where the problems start. Problems caused by bats in houses range from minor to life threatening. Hearing occasional squeaking or the rustling of bat wings in your attic, chimney, or walls can be a nuisance, and even a bit unsettling. It is also disturbing to find a baby or adult bat in the living areas of your home. If a bat is stuck and dies somewhere in your walls or elsewhere in your home, you may smell the unpleasant stench of the decaying bat. These problems are minor, but should not be ignored because eventually larger problems will develop.