Final answer:
Bats are considered mammals because they possess hair and mammary glands, which are characteristic features of mammals. The hair of bats provides insulation and sensory functions, while their mammary glands allow them to nurse their young with milk.
Step-by-step explanation:
Mammals are vertebrates that possess hair and mammary glands. They also have certain unique features of the jaw, skeleton, skin, and internal anatomy.
For a bat to be considered a mammal, it needs to have these characteristic features. Bats have hair, which can provide insulation, sensory information, protection, and coloration. Bats also have mammary glands that allow them to nurse their young with milk.
Learn more about Characteristics of Mammals