Mice sing singularly

Rodents make their ultrasound sounds more like a jet engine

Cousin sing complex ultrasound serenades - and they create these sounds in a unique way. © David de Lossy / thinkstock
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Unusual Singing: Mice generate their ultrasound chants in a unique way, as researchers have discovered. Because they do not use their vocal cords, but a focused air jet similar to a nozzle. Their technique is more akin to the whistling of a jet engine or a turbine than to normal sound production in the animal kingdom, as the scientists in the journal "Current Biology" report.

Male mice are real singers: they beguile their female partners with complex serenades, which are very similar to those of songbirds. These ultrasonic chants, which are not audible to us, are as individual as an acoustic fingerprint - they reveal affinities, fitness and even local dialects and there are "languages".

Surprising high-speed recordings

However, how the mice produce these ultrasound melodies was previously unknown. To find out, now Elena Mahrt of Washington State University and her colleagues have the processes in the throat of the rodents first observed using high-speed cameras. They filmed the larynx and vocal cords of mice at 100, 000 frames per second.

It was surprising that "we found that the mice produce the ultrasound in a way that has never before been seen in an animal, " says Mahrt. Contrary to expectations, the vocal cords of the mice remained completely motionless and quiet while they gave their ultrasound vocals. Therefore they could not be responsible for the sounds.

Nozzle-like airflow

"Instead, the mice direct a small stream of air from their trachea to the inner wall of their larynx, " Elemans says. "This creates the ultrasonic whistling." The unusual thing about it: "So far, this mechanism was only known from the noise generation in supersonic flows, such as vertical starting and landing with jet engines, " explains co-author Anurag Agarwal of the University of Cambridge. display

Even with turbines or fans for rapid cooling of electrical components, a whistling can occur, which is generated by a similar air flow. The sound is produced by interactions of the air flow with the environment. "The mice therefore use a very complicated and sophisticated technique to produce their ultrasound vocals, " says Agarwal. "Although mice have been studied so frequently and intensively, they still seem to have some cool tricks up their sleeve." (Current Biology, 2016; doi: 10.1016 / j.cub.2016.08.032)

(University of Southern Denmark, 11.10.2016 - NPO)