Mice may be able to learn to 'sing' in harmony like humans and some birds, according to US scientists.
Male mice sing complex songs to attract females, but it's long been thought they couldn't control their pitch (how high or low it sounds).
Duke University researchers have now found that when male mice were housed together, they changed the pitch of their songs to match each other.
But some scientists aren't so sure the evidence supports the new finding.
The melodies that mice make are ultrasonic, so they're too high-pitched for human ears.
Only a few animals are able to adapt the pitch of their sounds - something known as "vocal learning".
Creatures with this talent include parrots, whales, dolphins, bats and elephants.