Male Crickets Imitate Predator Chirps To Startle Potential Mates Into Revealing Location

A group of Lebinthine crickets perform an odd kind of duet to communicate, which researchers from Dartmouth College say likely evolved from males startling females into revealing their location. To test this theory, they studied female reactions to male songs and found that females actually shudder in response. 

"The origins of communication signals have long fascinated evolutionary biologists, and multiple potential mechanisms for these origins have been proposed," Hannah ter Hofstede, one of the study leaders and an assistant professor at Dartmouth, explained in a news release. "Our results demonstrate how sensory exploitation of anti-predator behavior can also evolve into a classic communication system that benefits both senders and receivers, and that this unexpected origin might be more common than previously appreciated."

Hofstede's field of research primarily focuses on how sensory systems evolve to encode the environmental cues that are crucial for an animal's survival and reproduction. For the recent study she was joined by co-authors from the University of Cambridge.

Crickets distinguish between mates and predators based on the frequency of sound: male crickets produce low-frequency chirps to attract females, while bats – a primary predator – emit high-frequency, or ultrasonic sounds for echolocation. Males have learned to emit high-frequency sounds, similar to those of predators, to startle potential mates. In females that manifest as a shaking of their whole bodies that produces a vibrational signal. 

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

Furthermore, neurophysiological recordings revealed that crickets in this high-frequency group no longer have the auditory neuron for coding low-frequency sounds responsible for phonotaxis – or moving in response to sound – in other crickets, researchers added. The crickets may have lost these neurons as a result of changing male calls, which sheds light on how communication systems can evolve over time.  

Their findings were recently published in the journal Current Biology. 

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