Uninvited guests. Using sheer numbers to claim a territory, some animal groups are considered "pests." But their very survival may depend on finding a home where they're not welcome. In this episode, we examine ants, rats, and bats.

pt. 1. Infestation: Rats -- pt. 2. Infestation: Sea Lions, Rats, Bats (Animal Empires Series) -- pt. 3. Infestation: Bats.