Which mammals really fly?

True flapping flight, almost as proficient as that of the birds, has been achieved by only one group of mammals, the bats. Bats probably evolved from a group of early insectivores that fed by leaping from the branches of trees to catch passing insects. It is interesting that bats fly by cupping their wings in front of the body and dragging this air behind them, rather than flapping their wings up and down.

Bats can be arranged into two large groups: fruit-eaters and insect-eaters. In general the fruit-eaters are large, can see well and fly in dim light. Insect eaters are usually smaller, have poor eyesight and have developed a good system of echo-location to enable them to fly in pitch blackness. By sending out series of ultrasonic squeaks and listening for the returning echoes with very efficient ears, the bats can navigate their way around obstacles and catch their insect prey in darkness.