This order includes all mammals that engage in true flapping flight using their forelimbs, commonly known as bats. The toes of their forelimbs are very long at metacarpal level and support a wing membrane called the patagium. The thumb ends in a sharp claw, while all other fingers have no claw. Their ears are large and are related to the echolocation function. Echolocation involves navigating a three-dimensional environment by emitting ultrasound, which is echoed from obstacles and received by the ears. This method of movement is suitable in areas where there is little or no light, such as in caves and grottoes. Chiroptera are nocturnal animals that spend their day at rest, hanging upside down. Their diet is extremely varied, with frugivorous, insectivorous, carnivorous, piscivorous and even exclusively haematophagous species.