An echo from the bat's first broadcast could masquerade as the echo from a subsequent broadcast. The bat overcomes this potentially confusing cascade of signals by making a template, or mental fingerprint, of each broadcast and corresponding echo, the team learned. That way, the bat needs only to slightly alter the frequency of its broadcast to create a broadcast/echo template that doesn't match the original. The team found that bats change the frequency of their broadcasts by no more than 6 kilohertz. That's a good thing, as bats' frequency range covers only roughly 20 to 100 kilohertz.
"They've evolved this, so they can fly in clutter," said Simmons, professor of neuroscience. "Otherwise, they'd bump into trees and branches."
Echolocating bats use rapid-fire broadcast-echo pairs to navigate through forests of obstacles. They make subtle changes in each broadcast to keep the pairs from blurring. These bats were flying at night through a forest in Belize.
(Photo Credit: James Simmons, Brown University)
A Brown University-led team strapped microphones onto heads of big brown bats and recorded the sounds they emitted and the echoes that returned to learn how bats detect objects in space and successfully maneuver around them.
(Photo Credit: James Simmons Lab, Brown University)
Source: Brown University