image: The bat shown here is emitting sounds. It will use echoes created by these sounds to stay on target even in cluttered environments. view more
Credit: James Simmons, Brown University
In a paper published in the July 29 issue of Science, James Simmons and Mary Bates of Brown University, along with researchers from the Republic of Georgia, reveal how bats expertly use echolocation to hone in on specific targets, such as prey organisms, without being distracted or set off course by background objects in their environments.
It has long been known that bats emit high frequency sonar blasts, and then construct a three dimensional picture of their environment based on returning echoes. But the new research, which was partially funded by the National Science Foundation, shows how bats interpret the cacophony of returning echoes to distinguish their priority target from background clutter.
Simmons explains that when a bat chirps, it waits for the corresponding echo; it makes a mental fingerprint of the emitted sound and its echo. If the broadcast/echo fingerprints match up precisely, then the bat "will process it and produce an image," Simmons said. In many cases, that image would be the bat's target object. But when the second harmonic is weaker in the echo fingerprint, the response from the bat's neurons' is delayed by as few as 3 microseconds. That momentary delay, while undetectable to humans, is enough to tell the bat that the object is present, but it is not its primary interest.
"The bat takes clutter and defocuses it, like a camera would, so the target remains highly defined and in focus," Simmons said.
For more information about this research, see the accompanying video and Brown University's press release.
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Science