"We started recording the vocalizations to assess the factors that lead to recognition of female pheromones but the vocalizations turned out to be much more complicated and interesting than we expected," says Timothy E. Holy, lead author of the report detailing the findings, published online today by the Public Library of Science Biology. "It's not yet clear whether singing conveys an advantage to male mice during courtship, as it appears to do in birds."
Although humans have long been listening to the serenades of birds and whales, among other animals, mouse songs have fallen on deaf ears for the past several decades, because they are out of the range of human hearing. When Holy and co-author Zhongsheng Guo started taping the ultrasonic utterances of 45 male mice, they quickly found that the high-pitched sounds exhibited repetitive phrases, or motifs, that varied over time but that were repeated with some regularity. In short, they qualified as songs.
The mouse songs, when dropped several octaves and put through an algorithm for easy human listening, sound not unlike the whistling of birds, though Holy points out that mouse songs lack some of the sophistication of their avian counterparts. "Perhaps the best analogy for mouse song would be the song of juvenile birds, who put forth what you might call proto-motifs and themes," he observes.
Although the lovestruck mouse's repertoire cannot compete with that of an adult canary, the singing of mice does offer an opportunity to potentially study the genetics of song learning, especially if mice learn from a "tutor" as many birds do. And the wild cousin of the lab mouse just may possess an even wider range. "Domestication has changed many aspects of mouse behavior," Holy remarks. "It would be intriguing to find out if [wild mouse] songs are more or less birdlike than the lab mouse songs."