Tuesday, 15 December 2015

Cricket's chirp may have 'predatory roots'

By Victoria Gill
Science reporter, BBC News

10 December 2015 

The song of the male Angnotecous obscurus cricket is of such a high frequency that it is difficult to hear

Scientists have discovered that the chirps of some crickets could be a cunning way to "startle" potential mates into revealing their location.

The Dartmouth College team discovered the insects' communication system and studied females' reactions to the males' songs.

They say the call is likely to have evolved from males impersonating hunting bats and startling females.

Females' shuddering response appears to allow males to locate a mate.

Close examination of females' nervous systems suggested that this shudder evolved from a startle reflex, the researchers say.

Lead researcher Prof Hannah ter Hofstede investigated this unusual insect duet after a colleague presented some recordings of the insects' particularly high frequency chirps.

"It struck me as very strange that these crickets would use such high frequencies for mating purposes," the scientists said.

Other cricket species avoid sounds at these frequencies, which are similar to the sounds that bats make when navigating and hunting.
Escape behaviour

Prof ter Hofstede used playback experiments - playing males' songs through speakers - to test females' reaction to the high, bat-like chirps.

"I expected the females to walk to the speaker, because this is the usual behaviour for female crickets, but they did not do this - [they instead] made a small jerking motion after each male call," she explained.

"From many observations of males and females together, I noticed that it was always the male walking to the female when she produced these vibrational signals."

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