Rodent Serenade

Mice sing to potential mates

02-01-2006 // Hannah Schardt

IF MICE could sing, how would they sound? Researchers at the Washington University of Medicine in St. Louis have come up with an answer, and it's not hypothetical. It turns out that male mice do sing--it's just that their serenades are pitched too high for humans to hear.

Neurobiologist Tim Holy studies how mice respond to pheromones. He knew that male mice make ultrasonic vocalizations when they smell female mouse scents. But it was purely by accident that he discovered those sounds are not mere squeaks--they're songs. Holy and his colleague, programmer Zhongsheng Guo, exposed male mice to female pheromones--in this case, the urine of female mice--and recorded their responses. They then lowered the recordings to a level audible to the human ear and used computer software to chart the sounds. Holy was shocked to discover that the vocalizations had a variety of syllable types and were organized into discernible patterns--the two requirements for the definition of "song." The mice would sing several notes of varying pitches, pause, then repeat the same pattern.

Holy says he doesn't know exactly why the mice sing, though he assumes that it has something to do with wooing a mate. "It does seem that female mice like to hang around singing males," he says, "though we don't know whether that translates into reproductive success."

Until Holy and Guo's study, the roster of singing mammals was thought to be limited to bats, whales, dolphins and, of course, humans. So might there be other animal songs being sung all around us? "I wouldn't be entirely surprised by that," says Holy. "Now, whether that extends outside the rodent family, I'm not sure. I'd be surprised if cats or dogs were singing. But then, I didn't expect to find mouse songs, either."

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