Theories About Target Ranging in Bat Sonar The frequency-modulated biosonar sounds transmitted by bats are well-suited to the accurate determination of target range and target

Introduction Echolocating animals achieve high levels of performance for guidance, orientation, and target finding in surroundings that go from simple, open spaces to densely cluttered scenes. Developing man-made radar and sonar systems that can perform at comparable levels has been an important motivation for studying echolocation from the time of its discovery (Griffin, 1958) to the present (Au and Simmons, 2007; Simmons et al., 2017). The most obvious comparison with man-made systems is with target ranging, determining the distance to an object from the outward and returning travel time of echoes. Figure 1 illustrates the problem of determining target range from echo delay. The earliest theories of echolocation recognized the distinction between a pulse and a chirp to explain target ranging. Inspired by these theories, behavioral studies established that bats do indeed perceive target range from echo delay (Simmons et al., 1995). Furthermore, they exploit the properties of their frequency-modulated (FM) signals to work back from long chirps to brief pulses (Simmons et al., 1996).