Mice court one another using ultrasonic love songs that the human ear cannot perceive, according to new research. It seems that the unique high frequency sounds are sung using a type of mechanism that has only been scientifically recorded in supersonic jet engines.
It's not only mice, but most rodents sing as part of their mating rituals. Mice, however, are used in studying communication disorders in humans, but the process through which they make the sound was unknown until recently. The discovery may help in developing more effective animal models in the study of speech disorders.
The study, co-authored at the University of Cambridge and recently published in the journal Current Biology, found that mice do sing. It was previously believed that the sound was produced by a mechanism similar to the tea kettle, or the resonance caused by the vibrations in the vocal cords.
The research invalidates both previous hypotheses, because mice sounds come from a small air jet from the windpipe against the inner wall of the larynx, which causes a resonance and produces an ultrasonic whistle.
An ultra-high-speed video of 100,000 frames per second helped the scientists show that the vocal folds don't experience any motion as the ultrasound comes from the mice's larynx.
"Mice make ultrasound in a way never found before in any animal," said the study's lead author Elena Mahrt, from Washington State University. The mechanism produces sound in supersonic flow applications, similar to jet engine vertical takeoffs and landings.
"Mice seem to be doing something very complicated and clever to make ultrasound," according to Anurag Agarwal, study co-author and head of the Aero-acoustics laboratories at Cambridge's Department of Engineering.
At the same time, it is likely that many rodents use ultrasound to communicate, according to Coen Elemans from the University of Southern Denmark and the study's senior author. However, not much is known about this entire process, and it's possible for other animal species use it, such as bats.
"The more we understand how mice make their social sounds, the easier it will be to understand what happens in a mouse brain that has the same genetic mutation as a human with a speech or social disorder," Mahrt added.
Ultrasonic vocalizations are crucial when it comes to linking gene mutations to mice behavior disorders, such as autism. The evidence disproves the two leading hypotheses that were followed until now. It does not, however, imply that the understanding of psychological and physical mechanisms in combining and generating acoustic features of the vocalization is possible for now, or that the underlying mechanics are accessible.
This study comes after another breakthrough involving mice. In July, another study was published about mice's reactions to film noir. Although the neural impulses were active during the first few minutes of the movie Touch of Evil, their brain activity changed in response to images.
