What sounds do you imagine dinosaurs made? Do you believe that a Tyrannosaurus blared with a thunderous roar? Do you think a Velociraptor let out a piercing scream?
“In the movies, we always see dinosaurs making a lot of scary noises, like lions and tigers and bears,” says Julia Clarke. She studies ancient animals at the University of Texas at Austin. But those cries are the creation of Hollywood sound artists. Real dinosaurs probably communicated very differently.
To learn what they might have sounded like, Clarke is studying animals that are alive today: birds. Birds are dinosaurs’ closest living relatives. “They’re actually living dinosaurs,” says Clarke. Birds and dinosaurs have many features in common, such as feathers and the drive to care for their young. These features aren’t seen in all reptiles.
Scientists suspect that the voices of dinos and birds were also alike. To find out, Clarke and her colleagues observe all kinds of birds from ducks and robins to emus. If many different birds make the same noise, it could be a sign that their dinosaur ancestors did too.
In a recent study, Clarke’s team examined more than 200 bird species. The researchers found that one-fourth of them sing with their beaks closed. They make these closed-mouth calls by pushing air into a pouch in their throats. “It expands like a balloon,” says Clarke. In large birds like ostriches, this produces a deep boom, like a note from a tuba or the rumble of a race car.
“It’s not a roar, which is an open-mouth sound,” says Clarke. “But it can still be extremely frightening.” Take crocodiles, for example. These reptiles are another relative of dinosaurs. When they’re calling to a mate or defending their turf, they growl with their mouths closed. “It’s likely dinosaurs shared this closed-mouth vocal behavior,” says Clarke.
But scientists don’t know for sure. The organs dinosaurs used to make sounds were made of soft tissue. So unlike their bones, these body parts rarely became fossils. That makes it much harder to reconstruct what a dinosaur’s voice sounded like.
Still, Clarke is hopeful that science can solve the puzzle. “We’re just getting started,” she says. “There’s a lot more we can learn if we take the time to listen.”