Female Mice Seduce Through Song

When male mice go cruising for chicks, they croon at ultrasonic frequencies — and it turns out that females accept their offers by joining in a duet.

If you stumble upon a pair of mice in your home, instead of freaking out, you might want to perk your ears and try to catch a tiny tune. Research from the University of Delaware indicates that when mice are feeling frisky, they can’t help but belt our their longings in song.

Scientists discovered that male mice serenade females a few years ago. Each male’s song is unique, and females make their choice based on complexity and endurance. The mating songs even help mice avoid inbreeding — daughters remember how their fathers sound, and make sure to avoid potential mates who remind them of their dads. These initial studies stated that females respond to the males they like by preening a bit more than normal and making sure they look their best.But the new study proves that mating songs aren’t a one-sided affair.

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Since mice sing at frequencies too high for humans to hear, the researchers set up an acoustic chamber with highly precise microphones and sound analysis instruments. The walls of the chamber were designed to reduce sound reflections that would interfere with data collection. Then, they let two pairs of male and female mice scurry around in the chamber to get to know each other.

In order to pinpoint the source of each sound, the researchers programmed Mouse Ultrasonic Sound Estimation software. This software uses the delays caused by the speed of sound traveling through air to analyze the sounds picked up by each microphone, tracing them to the mice’s movements which were linked to a tracking system.

As expected, the males sang as they pursued the females. But the sound analysis found that the females responded with their own vocal medley if they returned their suitor’s interest. Those females who sang back would also slow down during the chase so the males could catch up with them, playing a coquettish game of hard-to-get. The advantage to keeping their amorous arias in the ultrasonic range is that predators can’t hear them, and their activities are less likely to be disturbed.

The researchers believe that there may be even more to the mice’s high-pitched harmonies — they could help the mice communicate complex ideas that simple squeaks can’t convey and establish social hierarchies among the mice. The new software can help future studies tease out the specifics of mice communication via singing.

In particular, comparing the differential singing abilities among individuals can assist the ongoing efforts to build mouse models of autism. A paper published by a different team in February revealed that mice with a genetic condition associated with autism in humans had trouble producing the same types of squeaks and songs as the normal mice. Learning more about the ins and outs of mice melodies and how they’re integrated into social behavior may improve our understanding of how autism affects social development and communication.