Mice learn songs based on the sounds they hear

Mice may have the ability to learn songs based on the sounds they hear, according to US researchers.

They found that when male mice were housed together they learned to match the pitch of their songs to each other.

Mice also share some behavioral and brain mechanisms involved in vocal learning with songbirds and humans, say the researchers.

But some scientists are skeptical, saying the evidence doesn’t support the claim.

Details of the study are published in the Journal Plos One.

Previous research in this field has shown that male mice can sing complex songs when exposed to females and these play an important part in courtship.

These murine serenades are ultrasonic. At between 50 and 100KHz, they are far above the hearing range of humans. When processed to make them audible to humans, they sound like a series of plaintive whistles.

It has long been assumed that mice were incapable of modifying the sequence or the pitch of these sounds. This ability, called vocal learning, is rare in the natural world. It is restricted to some birds such as parrots and song birds along with whales, dolphins, sea lions, bats and elephants.

But in these experiments, researchers from Duke University in North Carolina say they found that mice have both the brain circuits and the behavioral attributes consistent with vocal learning.

Dr. Erich Jarvis, who oversaw the study, said it had changed his understanding of the way mice make sound.

“In mice we find that the pathways that are at least modulating these vocalizations are in the forebrain, in places where you actually find them in humans,” he said.

He says the study does not have clear evidence that mice have the very same vocal abilities as birds and humans. He believes there is a spectrum where different species have vocal skills to different degrees.

“We think mice are intermediate in this ability between a chicken and a song bird or even a non human primate and a human,” Dr. Erich Jarvis said.

When male mice with different vocal pitches were housed together, the team found that the pitch of their songs gradually converged over a period of eight weeks.

Dr. Erich Jarvis argues that this is an important development: “When we put a female in the cage with two males, we then found that one male would change his pitch to match the other. It was usually the smaller animal changing the pitch to match the larger animal.”

But others are less certain. Dr. Kurt Hammerschmidt, an expert in vocal communication at the German Primate Centre in Goettingen, cast doubt on the study’s claim about the vocal behavior of male mice.

“The pitch convergence story is less convincing,” he says.

But Erich Jarvis refutes this, saying the skepticism is unfounded.

“His complaint was that we don’t have enough animals, but we found this in 12 mouse pairs and in every single pair… at least in our eyes it’s quite reliable and statistically significant,” he said.