Bats could inspire new radar systems

A similar problem arises when a bat chases a moth through thick foliage. Signals bouncing off the leaves can overlap and set up interference.

In both cases, the result should be confusion and the creation of ''phantom'' objects which are not there, but bats avoid the problem by tweaking the frequencies of the sounds they emit, researchers found.

The study could help scientists learn new ways of developing radar and sonar equipment to avoid potential interference from electronic machinery.

The creatures also take a mental snapshot of each broadcast and the echo it produces to differentiate one signal from another.

To investigate how they cope with crowded environments, scientists mounted tiny microphones on the heads of big brown bats (Eptesicus fuscus).

They recorded sounds the bats emitted while navigating through an obstacle course of plastic ceiling-to-floor chains.

Other microphones placed in the room recorded the echoes produced from the bats' broadcasts. At the same time, the bats were filmed with high-resolution video cameras.

The recordings showed the bats were faced with a potentially confusing cascade of overlapping echoes.

They appeared to get around the problem by logging a ''mental fingerprint'' of each broadcast and corresponding echo in their memories. That allowed them to separate signals by very slightly altering their frequencies so one did not match the other.

The bats were found to change the frequency of their broadcasts by no more than six kilohertz.

Professor James Simmons, from Brown University in Rhode Island, America, who led the study, said: ''They've evolved this so they can fly in clutter. Otherwise, they'd bump into trees and branches.''

The research appears today in the journal Proceedings of the National Academy of Sciences.


/Telegraph.co.uk/