Songbirds may be the Sinatras of the animal world, but male mice can carry a tune too, say Washington University researchers who were surprised by what they heard.
Scientists have known for decades that male lab mice produce high-frequency sounds - undetectable by human ears - when they pick up the scent of a female mouse. This high-pitched babble is
presumably for courtship, although scientists are not certain.
But it turns out those sounds are more complex and interesting than previously thought.
"It soon became apparent that these vocalizations were not random twitterings but songs," said researcher Timothy Holy. "There was a pattern to them. They sounded a lot like bird songs."
To make their point, the researchers provided audio recordings of the sounds, which have been modified for human ears. The recordings do indeed sound birdlike.
The findings by the researchers at Washington University School of Medicine in St. Louis are published online Tuesday in the journal Public Library of Science Biology.
If the analysis by the researchers is confirmed, mice can be added to the short list of creatures that sing in the presence of the opposite sex, including songbirds, humpback whales, porpoises, insects and, possibly, bats.
"There was joy in this discovery," Holy said. "We didn't expect it."
The finding opens the possibility of using mice to study and develop treatments for
autism and other communication disorders, said Holy, the lead author and assistant professor of neurobiology and anatomy at the university's medical school.
Bird song is used to understand how the human brain works. But some questions might be posed better with mice, for experimental convenience, he said.
If it is true that the male mice are producing songs, it raises questions about how their sounds develop and whether mice - like birds - are able to learn new sounds, said animal communication expert Peter Marler, a behavioral neurobiologist at University of California, Davis.

(Agencies)鸣雀也许是动物世界中的法兰克·辛纳屈（能歌能演的全能艺人，曾演唱过多首经典歌曲），然而，雄性老鼠同样可以发出“曲调优美”的声音。华盛顿大学的研究者们在实验室中听到了雄性老鼠有规律的叫声，这着实让他们吃了一惊。
几十年前科学家们就知道，当实验室中的雄性老鼠闻到雌性老鼠的气味时，会发出高频率的声音，这种声音人耳通常是无法察觉的。据推测，雄性老鼠发出这种含糊不清的高频声音是在求爱，尽管科学家对这一点还不是很确定。
但这种声音要比以前认识的复杂得多，也有趣得多。
“很快，我们就知道这些发声法不是杂乱无章的喋喋不休，而是歌声。它们有固定的形式，听上去更像鸟儿的歌声，”研究者蒂莫西·霍利说。
为了证明他们的观点，研究者们提供了雄性老鼠发出声音的录音，经过处理后人耳可以听得到，这些录音听上去确实很像小鸟的声音。
华盛顿大学圣路易医学院的研究者们周二把研究结果发表在生物学公共图书馆的网站上。
如果研究者们的分析能够得到证实，老鼠可以加入会在异性面前“唱歌”的生物之列，这类动物包括鸣雀、座头鲸、昆虫，可能还有蝙蝠。
“这个发现很有趣，我们没有想到这样的结果。”他说。
这一发现使得用老鼠来做研究，开发治疗孤独症和其他沟通障碍成为可能，霍利说。他是这个研究报告的主要作者，也是华盛顿大学医学院神经生物学和解剖学的副教授。
小鸟的歌声通常被用来了解人脑的工作方式，如果这个发现被证实的话，可以用老鼠来做实验，这样会更方便，也会提出更多问题。
如果雄性老鼠真的会“唱歌”的话，那么问题就是它们的声音是怎么发出来的，还有老鼠是不是也像小鸟一样能够学一些新的声音，动物沟通专家彼得·马勒说，他是美国加州大学戴维斯分校行为神经生物学家。