Bats and Whales have several dissimilar characteristics. Bats are flying mammals with wings made of skin stretched over their bones, while whales are aquatic mammals that live in water and have streamlined bodies adapted for swimming. Bats primarily use echolocation for navigation and hunting in the air, whereas whales use sound for communication and navigation in the ocean. Despite these differences, their shared mammalian traits classify them together in the class Mammalia.

Bats and whales belong to the same class, Mammalia, because they share key characteristics typical of mammals, such as being warm-blooded, having fur or hair at some stage in their lives, and nursing their young with milk produced by mammary glands.