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Hunting Adaptation: Bats Sneak Up on Moths

Sep 11, 2015 04:08 PM EDT
One of the many bats that live in locations worldwide, except in polar regions.
The barbastelle bat, a type that is somewhat rare but found throughout Europe, uses “stealth echolocation” to hunt eared moths.
(Photo : Flickr: Bernard Dupont)

Some animals use biological sonar to listen for the echoes of their calls, in order to navigate and hunt. Bats are one example of such animals. However, barbastelle bats may have a slightly sneakier approach, according to reserachers from the University of Tübingen, Germany.

The barbastelle bat sends two different types of weak echolocation signals that are much weaker in sound than those of other aerial bats, according to a news release. This technique, referred to as "stealth echolocation," is low intensity, which prevents moths from detecting the bats signals early on and allows the bat to snatch up its dinner more easily.

The researchers discovered that the barbastelle bat uses its two signals alternately while hunting. One signal is set upward through the nose so that they can sneakily find prey, while the other signal is downward through their mouth in order to keep track of their environment.  When observing the bats' signals, the researchers used microphones to determine source level and sonar beam direction. In total, the observed more than 300 wild bat calls in central France.

Nostril Alignment in Bats
(Photo : (A,B) Christian Dietz; (C) Johanna Hurst; (D) Anna-Maria Seibert; (E-H) Laurent Arthur. )
Differing nose alignment of four bat species. The upper row illustrates a top view and the bottom row shows a front view of barbastelle bat noses.

The researchers explain that this difference in the barbastelle bats may be a result of their adapting to their targeted prey: The eared moth. They further explained that these bats may have evolved the downward-directed signals to compensate for the disadvantage they face when using a weaker upward signal. When they use a "stealthier" upward signal to sneak up on the moths, they reduce their detection in the environment below.

Their findings were recently published in PLOS ONE

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