Study reveals that high-pitched ‘singing’ varies according to to social context, placing mice in an elite group of animal vocalisers





They may stop short of singing The Bells of Saint Mary’s, as demonstrated by the mouse organ in Monty Python, but scientists have discovered that male mice woo females with ultrasonic songs.

The study shows for the first time that mouse song varies depending on the context and that male mice have a specific style of vocalisation reserved for when they smell a female in the vicinity.

In turn, females appear to be more interested in this specific style of serenade than other types of squeak that male mice produce.

“It was surprising to me how much change occurs to these songs in different social contexts, when the songs are thought to be innate,” said Erich Jarvis, who led the work at Duke University in North Carolina. “It is clear that the mouse’s ability to vocalise is a lot more limited than a songbird’s or human’s, and yet it’s remarkable that we can find these differences in song complexity.”

The findings place mice in an elite group of animal vocalisers, that was once thought to be limited to birds, whales, and some primates. Mouse song is too high-pitched for the human ear to detect, but when listened to at a lower frequency, it sounds somewhere between birdsong and the noise of clean glass being scrubbed.

The Duke University team recorded the male mice when they were roaming around their cages, when they were exposed to the smell of female urine and when they were placed in the presence of a female mouse.

They found that males sing louder and more complex songs when they smell a female but don’t see her. By comparison, the songs were longer and simpler when they were directly addressing their potential mate, according to the findings published in Frontiers of Behavioural Neuroscience.

“It’s like they make more effort to bring the female nearby. Once she’s within reach, the game is already won and they focus more on mating behaviours,” said Jonathan Chabout, a neuroscientist at Duke University, and co-author.

Appearing to confirm this interpretation, the scientists found that female mice showed more interest in the “calling” serenade, when they were placed in a tunnel with the two types of song playing through speakers at opposite ends.

The scientists said that female mice may use the quality of a male’s singing as an indicator of whether they are of good genetic stock. More complex sequences of sounds might indicate that the male has other desirable qualities, such as better than average memory, for instance. Mice may also use vocal signatures to recognise each other, the authors speculated.

Some of these questions may be resolved thanks to a global database, Mousetube, that researchers have set up to upload mouse sounds for others to use in their own experiments.

The discovery that mice are capable of complex vocalisations could make them a more helpful model for studying conditions involving language problems.

Last month, a separate team found that mice with a genetic variant sometimes seen in autism have “stunted squeaks”, for instance.

Mu Yang, who led this work at University of California, Davis, said that she would classify mouse song as social signals, rather than intentional communication.

“If someone hit you, you might yelp “Ouch!” then ask “Why did you hit me?!” The “Ouch” part is emitting a signal, a almost physical response. The “why did you hit me?” part is communication - a signal that means to elicit a meaningful reply,” she said. “In my opinion, mouse vocalizations are more likely to be signal emitting than to communication. There are autistic individuals who are non-verbal or problems with uttering words, and mouse vocalization may be suitable for modelling these deficits.”