Animal echolocation in the external ear. There are two hypotheses about the evolution of echolocation in bats. The first suggests that laryngeal echolocation evolved twice in Chiroptera, once in the Yangochiroptera and once in the horseshoe bats (Rhinolophidae). The second proposes that laryngeal echolocation had a single origin in Chiroptera, was subsequently lost in the family Pteropodidae (all megabats), and later evolved as a system of tongue-clicking in the genus "Rousettus". Individual bat species echolocate within specific frequency ranges that suit their environment and prey types. This has sometimes been used by researchers to identify bats flying in an area simply by
Bat species identification (or "Pips") give good examples of what can be discovered with a bat detector and make a good start to learning how to identify bats. Bat detectors pick up various signals in the ultrasound range, not all of which are made by bats. To distinguish bat and bat species it is important to recognise non-bat species. Captured bats can be exactly identified in the hand but in many countries a licence is required before bats can be captured. There are four basic types of bat echolocation call. The term "frequency modulation" (FM) refer to the "chirp" type of bat call.