Mice can sing.

Humans can’t hear it, but researchers say the ultrasonic songs of male mice trying to woo females are comparable to the musical trills produced by songbirds.

That mice make noise is nothing new to those who have had them in their houses, and scientists have known for decades that male mice will make sounds when they are near females, or exposed to female pheromones. Now they say that those utterances are love songs.

First, the researchers let male mice sniff cotton swabs dipped in female mouse urine, which contains chemical compounds known as pheromones that can signal sexual status. Then the researchers recorded the reactions of the mice.

As expected, the males produced noises that were beyond the upper limit of human hearing. But when the researchers slowed the recordings to one-16th the normal speed, they heard calls that sounded like low, intermittent whistles. They also dropped the pitch to an audible level, and heard shrill chirps that sounded remarkably like bird songs.

“It was very surprising. The real moment of discovery came when I first wrote the software to transpose the songs into our hearing waves. I said, ‘My gosh, these things sound like songs,’ ” Dr. Holy said.

A computer analysis showed the sounds meet key definitions of songs, he said. There are distinct categories of sound, instead of just one note repeated over and over again. There are also recurring themes, such as the melodic hook in a catchy tune, he said.

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