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
Large slit-faced bat fly over long distances. Although smaller bats are consumed by "N. grandis", they are only eaten when they fly into the roosts of "N. grandis". "N. grandis" produces low-intensity echolocation calls at high frequencies, which makes them nearly inaudible except at close range. Instead of relying on echolocation to find their prey, these bats listen for wing fluttering of smaller bats and even insects. However, as "N. grandis" gets closer to its prey during a hunt, it exudes a louder echolocation call. At the beginning of the pursuit, the call ranges from 17-114 kHZ, and rises to a range of