Here's why:
* Placental mammals are characterized by giving birth to live young after a period of gestation where the developing offspring receives nourishment through a placenta.
* Bats, like humans and most other common mammals, fit this description.
* The other two main categories of mammals, monotremes (lay eggs) and marsupials (give birth to underdeveloped young that complete development in a pouch), do not include bats.