Nov. 3, 2005 — Their voices may be squeaky, but mice sing, according to a new study.

Several years ago, scientists discovered that male mice emitted ultrasonic vocalizations when the mice were trying to woo females. But the latest study, published in the current journal Public Library of Science Biology, is the first to classify the sounds as songs and to make them audible to human ears by lowering their ultrahigh pitch and slowing them down.

Timothy Holy, who co-authored the study with Zhongsheng Guo, told Animal Planet News that there is no universally agreed upon definition for "song" among scientists, but he believes, "Songs are long sequences of vocalizations, preferably containing more than one type of sound, with some kind of regular sequence to the syllable types."

Holy, an assistant professor of neurobiology and anatomy at the Washington University School of Medicine, added, "By that definition, mouse vocalizations are clearly songs, because they easily satisfy all (of) the criteria."

Some people may sing for their supper, but the researchers determined that male mice sing for sex since singing seems to facilitate courtship.

The scientists induced the male vocalizations by wafting cotton swabs soaked with the urine of female mice in front of male mouse noses. The urine contained sex pheromones, which are chemicals that can signal to the male that a female is ready for mating.

The scientists then used specially designed computer software to analyze and chart the components of lab-raised male mouse sounds.

Holy admits that mice are not the best singers on Earth. Humans, humpback whales and many birds croon more complex melodies, but mice are not the simplest singers either, he believes.

For example, "singing" insects and certain amphibians only repeat certain syllables in their sound creations, he explained.

Holy has not ruled out that female mice can sing, and he also hopes to study the vocalizations of wild male mice, which may produce more complex sounds than that of their laboratory mice counterparts.

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