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6-Nov-2014

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Bats emit 'interference' that leaves competing bats hungry



Mexican free-tailed bats emit specialized signals that jam the echolocation of other bats competing for insect prey. The accompanying composite image depicts two bats competing for prey and a visual rendering of the jamming call.
[Credit: Nickolay Hristov]

Bats on the trail of a tasty insect miss capturing their prey when competing bats nearby make a special interfering call, a new study published in the 7 November issue of the journal Science shows.

To locate and identify food in the environment, bats make calls and listen to the echoes they return as these sounds bounce off objects, like bugs. This is called echolocation and it allows bats to be a leading predator after the sun sets.

But as this new study shows it also leaves bats vulnerable to something called "jamming."

Through a series of experiments, Wake Forest University's Aaron Corcoran and colleagues showed that Mexican free-tailed bats which make at least 15 different types of calls make a specialized sound that jams the echolocation process of other bats of their species, preventing them from gobbling up all the insect food.

The researchers took audio recordings of Mexican free-tailed bats as they competed for food at two outdoor sites in Arizona and New Mexico.

One sound the researchers captured a fast call that gets faster as the bats hone in on insect prey is called the "feeding buzz;" it allows a bat to get a better sense of an insect's position in the final moments of a chase.

The researchers captured other sounds, too, including a previously unstudied call that they observed a bat only made when another bat nearby was engaged in a feeding buzz.

Playbacks of the latter call to individual chasing moths made these bats 73.5% less successful at capturing their moth meal. This is because the jamming call disrupts the feeding buzz echolocation, the researchers say, interfering with the hunting bat's ability to determine prey position.

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