The Navy Drafts Bats

Bats share a remarkable ability with dolphins: Both groups of mammals use a biological sonar system that enables them to navigate confidently in total darkness - the bats at night and the dolphins in the murky depths of the sea. The U.S. Navy, meanwhile, has a problem with explosive mines - cheap and readily available weapons that can damage or sink a ship.

To avoid mines (and many other undersea hazards), the Navy mimics the echolocation system of bats and dolphins. But, reports National Geographic News, “conventional sonar systems designed by humans … are not nearly as sophisticated as the ones that have evolved in bats and dolphins.”

“We would like to emulate this capability for the quick, accurate detection and classification of buried mines,” Harold Hawkins, a program manager with the biosonar program at the Office of Naval Research in Arlington, Virginia, told National Geographic. The goal is to better understand how the two mammals emit sounds and process the echoes to create a three-dimensional reconstruction of the objects in their environment.

That's where James Simmons comes in. A neuroscientist at Brown University in Providence, Rhode Island, Simmons studies the echolocation system of bats. And he collaborates with dolphin researchers at the Navy Marine Mammal Program in San Diego, California.

The Navy is already using trained dolphins, which are carried in holding tanks on warships, to help detect mines. The Navy hopes Simmons' work with bats might help them build a sonar system that's good enough to let the dolphins retire.

Portrait of a big brown bat (Eptesicus fuscus)

Simmons works with big brown bats (Eptesicus fuscus), which are found throughout much of North America. “We do experiments that measure how accurately [the bats] determine the timing of echoes and how they form images of scenes,” he said.

And his team is finding that bat echolocation is so precise that bats can differentiate between sounds that are just two- to three-millionths of a second apart. That, National Geographic says, lets bats tell the difference between objects separated by the width of a human hair.

That's more precision than most bats would need to chase down flying insects at night, so Simmons set out to determine what else bats might do with their sonar.

Filming bats with an infrared camera that records body heat, the researchers watched bats zipping across the sky like comets. “We see them doing things never imagined,” Simmons said.

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