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Under infrared light, a large, winged object locks onto and overtakes a small blip while a radarlike display tracks the entire proceeding. This isn't a military exercise; it's an experiment designed to understand how bats use sonar to capture their prey.
Bats emit high-frequency sounds when hunting and navigating, but no one knew how they aimed these sonar beams until neuroethologist Cynthia Moss and graduate student Kaushik Ghose created a bat cave in their laboratory at the University of Maryland, College Park. The researchers padded a large room with acoustic foam and set up two high-speed infrared cameras and 16 strategically placed microphones. Then they introduced a large brown bat and a praying mantis.
The drama unfolds in a two-frame multimedia presentation. In the left frame, a slowed-down movie captures the visual action, complete with bat chirps and a crunch when the mantis meets its fate. On the right, an animated diagram traces the hunt from above and incorporates the microphone data to pinpoint the direction of the bat's sonar (represented by the darker bars on the gray-scale cone). The presentation reveals that a bat "locks its beam on a target" when hunting, says Ghose, who notes that the behavior is akin to baseball players keeping their eye on the ball.
"This is a unique visualization of an amazing event," says panel of judges member Thomas Lucas. He says the judges were impressed with the combination of video, sound, and sonar that puts the viewer in the bat's world. "This is something we never get to see," says Lucas. "It always happens in the dark."
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