We believe that all dinosaurs roared ferociously like what we see in movies but a new study claims that this is, in fact, inaccurate. A new study published online in the journal Evolution says that some dinosaurs simply mumbled or cooed with closed mouths like some birds today.

The findings are from a study about the evolution of how birds, also known as the dinosaurs’ descendants, emit sound with closed-mouth vocalization, which they use to attract potential mates and defend their territory.  The researchers say this closed-mouth vocalization demonstrate how dinosaurs made sounds.

Like the birds, dinosaurs could have also pushed air toward their esophageal pouch to produce booming sounds from their skin in the neck area while their mouths were closed. Unlike the sounds produced when the mouths are open, these closed-mouth sounds are quieter and lower in pitch.

dinosaurs

Some dinosaurs cooed like what doves do. Credit: Tobias Riede

The researchers from the US studied how common this skill is to birds and some reptiles. They  determined that out of 208 birds they studied,  52 bird species emit sound through closed-mouth vocalization.

“Looking at the distribution of closed-mouth vocalization in birds that are alive today could tell us how dinosaurs vocalized,” adds the study’s co-author Chad Eliason, a postdoctoral researcher at The University of Texas Jackson School of Geosciences. “Our results show that closed-mouth vocalization has evolved at least 16 times in archosaurs, a group that includes birds, dinosaurs and crocodiles.

Only birds the same size as a dove or bigger are capable of doing this behavior. According to the study’s first author Tobias Riede, a physiology professor at Midwestern University, closed-mouth vocalizations need a larger body size because a smaller body size is incapable of handling the tension of producing such sounds.

The research team admits that further investigations are still needed but they believe that some dinosaur s produced closed-mouth vocalizations depending on several factors, including behavioral or environmental reasons. Moreover, we still need to find a direct fossil evidence that can show us how dinosaurs sounded like.