Study Says Mice Join Cast of Singing Mammals

Nov. 1 2005 Canada

Far above the range of human hearing, male mice are warbling what may be love songs that are remarkably birdlike, according to a study in the Nov. 1 Public Library of Science Biology journal.

Excited by the scent of a female, each of the laboratory-bred minstrels has a signature ultrasonic song, said lead author Timothy Holy in an interview yesterday. The black mice join humans, whales and bats in the small group of mammals that sing, researchers said. The scientists said they found unexpected richness, including several syllable types organized into phrases and motifs.

He confirmed his hunch about the tunes by listening to the recordings at a pitch four octaves lower, at the original speed. Mice have been recorded at 20 hertz to 100 kilohertz. Humans hear sounds up to about 23 kHz, while a traditional mouse predator, the cat, can hear noise as high as 64 kHz.

The scientists had started out only to record the amount of vocalizations by male mice exposed to scents from females, males or a mix of the two. We actually kind of stumbled into this by accident, Holy said. We went into this not expecting their vocalizations to be very interesting. The main characteristic that we focused on was whether there was a pattern or a sequence of syllables, Holy said. My speculation is that courtship is the function.

Bird song is defined by function, such as courtship or territory defense, said Miyoko Chu, science editor for the Cornell Laboratory of Ornithology in Ithaca, New York, in an interview last week. Some of the songs have syllables and syntax, she said. They actually have a very specific audience, Chu said. They're actually singing to a male or female.

The mouse research was financed by the National Institutes of Health and the Pew Charitable Trusts' Pew Scholars Program in the Biomedical Program. The mice, each of which weighed about 1.2 ounce, produced songs that in their altered state sounded most like juvenile swamp sparrows or winter wrens, Holy said. The analogy in humans is a matter of debate, he said. It's not clear whether the best analogy is human song or human speech, Holy said.