- The radar system used by bats to navigate in the dark
is more sophisticated than previously known and can even help the flying
mammals to distinguish between different types of tree.
-
- Bats carry out a complicated statistical analysis of
the world around them using their echolocation system, according to a new
study. It means that they can paint a wide-angle picture of the night-time
landscape through which they fly, as well as being able to identify individual
objects such as insects and fruit.
-
- The creatures are known to navigate by emitting high-pitched
calls and listening to the echoes, much as a submarine sonar listens to
acoustic reflections. But a bat's sonar generates an immense amount of
background noise or "clutter" which until now was thought to
be extraneous information and was ignored.
-
- The latest study shows that this information is in fact
carefully assimilated into a sophisticated three-dimensional image of the
surrounding area, according to Lutz Wiegrebe and his colleagues from the
Ludwig-Maximilians University in Munich.
-
- "We've shown that bats use this information for
a purpose - to help them to navigate by contributing to a meaningful acoustic
image of the bat's surroundings," Dr Wiegrebe said.
-
- Bats do this by performing a kind of mental calculation
of the amount of surface "roughness" or "smoothness"
reflected from each object, which allows them to distinguish, for instance,
between a pine tree and an oak. Dr Wiegrebe, whose research was published
in the journal Proceedings of the National Academy of Sciences, said a
bat emits up to 100 calls or "clicks" per second and the echoes
coming back from nearby objects must be processed instantly for the mammal
to navigate at speed through complicated terrain.
-
- "They are able to analyse how the amplitude of an
echo changes over time. If this occurs quickly then the surface of the
object is rough; if it is slower then the surface is smooth," he said.
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- © 2004 Independent Digital (UK) Ltd http://news.independent.co.uk/world/science_medical/story.jsp?story=506493
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