Mice court one another with ultrasonic love songs that are inaudible to the human ear using a mechanism that has only previously been observed in supersonic jet engines, scientists including one of Indian origin have found.
Mice, rats and many other rodents produce ultrasonic songs that they use for attracting mates and territorial defence.
These 'singing' mice are often used to study communication disorders in humans, such as stuttering, said researchers, including those from University of Cambridge in the UK.
However, until now it was not understood how mice can make these ultrasonic sounds, which may aid in the development of more effective animal models for studying human speech disorders.
The new study has found that when mice 'sing', they use a mechanism similar to that seen in the engines of supersonic jets.
"Mice make ultrasound in a way never found before in any animal," said lead author Elena Mahrt, from Washington State University in the US.
Earlier, it had been thought that these 'Clangers'-style songs were either the result of a mechanism similar to that of a tea kettle, or of the resonance caused by the vibration of the vocal cords.
In fact, neither hypothesis turned out to be correct. Instead, mice point a small air jet coming from the windpipe against the inner wall of the larynx, causing a resonance and producing an ultrasonic whistle.
Using ultra-high-speed video of 100,000 frames per second the researchers showed that the vocal folds remain completely still while ultrasound was coming from the mouse's larynx.
"This mechanism is known only to produce sound in supersonic flow applications, such as vertical takeoff and landing with jet engines, or high-speed subsonic flows, such as jets for rapid cooling of electrical components and turbines," said Anurag Agarwal from Cambridge.
"Mice seem to be doing something very complicated and clever to make ultrasound," he added.
"It seems likely that many rodents use ultrasound to communicate, but very little is known about this - it is even possible that bats use this cool mechanism to echolocate," said Coen Elemans from the University of Southern Denmark, in Denmark.
"Even though mice have been studied so intensely, they still have some cool tricks up their sleeves," Elemans said.
The study was published in the journal Current Biology.
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