Mouse song recorded with ultrasonic microphones

Mice are natural born singers. But, unlike birdsong, it's inaudible to human ears. This mouse song was recorded by scientists in Vienna using ultrasonic microphones.

Dr. Sarah Zala, Konrad Lorenz Institute of Ethology, University of Veterinary Medicine, said: "We are recording mice singing.... we're using special microphones because we cannot hear the mice when they're singing because they sing in ultrasonic vocalisations. And we're interested in knowing how they sing and why they do it; the function of singing."

Humans can't hear above a range of about 20 kHz, but wild mice can sing up to about 120 kHz.

"In order to hear them, you have to bring the frequency down. And then when you hear them then it sounds like a song, like a bird," Dr. Sarah said.

Working with specialists from the Acoustic Research Institute they've built the Automatic Mouse Ultrasound Detector, or A-MUD. It's helping them pinpoint and isolate mice vocalisations far more precisely than previous methods. Research published recently in PLoS ONE says it's revealing clues about their social behaviour. And presenting some confusing results, such as why some wild mice are reluctant to sing under lab conditions.

Dr. Sarah said: "Why do the wild mice males not sing? I want to know this. I really want to know this because it doesn't make any sense. If they attract mates, so you would expect them to sing to attract mates so it must have costs in the wild probably - we don't know."

They're now eavesdropping on mice in more natural conditions in a bid to understand. It's research, they say, that could shed light on the evolution of vocal learning, and help neuroscientists better understand human speech disorders.