A bat navigating a pitch-black cave is not feeling its way through the dark; it is listening to a picture built from echoes. The bat emits a burst of sound far above human hearing and times the return of each echo, using the delay to judge distance and the pattern of returning frequencies to judge shape and texture. Some species even adjust the pitch of their calls as they close in on prey, sending faster, higher bursts as the target nears, the way a driver might glance more frequently at a mirror when traffic tightens. Researchers now borrow the underlying principle for engineered sonar, though no artificial system yet matches a bat's precision in a cluttered space.