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Fruit bat's echolocation may work like sophisticated surveillance sonar

New research suggests that the Egyptian fruit bat is using similar techniques to those preferred by modern-day military and civil surveillance. The results could inspire new directions for driverless cars and drones. While most other bats emit high-pitched squeals, the fruit bat simply clicks its tongue and produces signals that are more like dolphin clicks than other bats' calls. Fruit bats can also see quite well, and the animals switch and combine sensory modes between bright and dark environments. An earlier study showed that Egyptian fruit bats send clicks in different directions without moving their head or mouth, and suggested that the animals can perform echolocation, the form of navigation that uses sound, better than previously suspected. In measuring echolocation signals from fruit bats with a 3-D array of microphones, the researchers did not solve the mystery of the seemingly motionless tongue clicks, but they did notice something strange. The beam of different frequencies of sound waves emitted by the bats do not align at the center and form a bullseye, as one would expect from a simple sound source, but instead the beam of sound is off-center at higher frequencies. The researchers recognized the pattern as a common one in radar and sonar surveillance systems. Invented in the early 20th century and now used throughout civil and military applications, airplanes, ships and submarines emit pulses of radio waves in the air or sound underwater, and then analyze the returning waves to detect objects or hazards.

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