Mice Speak a Surprisingly Sophisticated Language of Love

​When it comes to romance, nothing tops a good old-fashioned love song. Making one's amorous intentions known through music is a very successful seduction technique spanning many species, from humans to birds to whales.

In fact, even mice wax romantic through song. These ultrasonic vocalizations (USVs) are too high-pitched to be detected by the human ear, but scientists can capture them on ultrasonic recording devices.

That's exactly what a team of neuroscientists based out of Duke University endeavored to do, and the results indicate that mice speak a surprisingly sophisticated language of love. Not only does this advance our understanding of non-human linguistics, it also has the potential to shed light on many neurological disorders in humans—autism, for example. The team's findings were pu​blished today in The Frontiers of Behavioral Neuroscience.

"Our lab is now focusing on the mechanisms involved in USV production and development of vocal brain pathways," lead author Jonathan Chabout, who is based at Duke's Erich Jarvis Labo​ratory, told me. "We aim to study the role at different pathways, genes, and brain areas that control this behavior, including where in the brain is the decision to sing a more complex versus simple song."

Male mice sing different songs depending on where females are. Credit: Jon​athan Chabout, Duke University.

Along those lines, Chabout and his colleagues found that male mice will alter the complexity of their serenades depending on whether or not females are in their direct line of sight. Males that could see females sang straightforward love ballads, while males that were exposed to female urine—suggesting the presence of the opposite sex, if not a direct visual—emitted much more complicated vocalizations.

"Although many species use vocalizations to attract mates, it is not common that animals will produce more complicated vocalizations when the opposite sex in not around in sight," Chabout said. "Male zebra finches will produce more varied, undirected songs in the absence of a female, but some people believe [it] is used for practice as opposed to courtship."

This isn't the only communication quirk the mice exhibited. Another interesting detail is that the overwhelming majority of mouse singers are male, with females rarely emitting any sounds at all. In fact, Chabout said that devocalized females will make about the same amount of noise in the presence of males as a group of normal females. Muting the voice of the males, however, results in protracted silence.

"So far our evidence indicates that the female mice are not singing back," he said. "The females do make some isolated vocalizations, but this is not song—just a long series of continuously produced syllables."

"That is, females have the ability to do it," Chabout added. "They just don't do it, or do it less when paired with a male."

Ever since scientists first discovered that mice had their own language some 50 years ago, there has been an ongoing campaign to figure out mouse "syntax," as the study's authors call it. These efforts have culminated in a delightful online repository of U​SVs called MouseTube, which is run by the Institute Pasteur in Paris (and to which Chabout's team contributed their own recordings).

MouseTube promo. Credit: mouseTube/Yo​uTube.

Decoding the secret language of mice has all kinds of applications for applied research into neurological conditions, especially those that inhibit social interaction, communication, or speech.

"Multiple labs around the world study mouse vocalizations as a model for autism spectrum disorders," Chabout told me. "Deficits in social vocal communication is one of them. Autistic children (and adults) have communication impairments, and it has been shown that mice models with similar genetic changes show some impairments in the way they emit USVs."

"Having a better understanding of the mechanisms and different social contexts involved in USV emission," he added, "will definitely help this research."