Now what was that roar again about dinosaurian noises? New research shows that they certainly did not roar, but cooed and mumbled!
Amazingly, scientists liken the cooing of dinosaurs to those of doves, which emit sounds through the skin and neck area even though their beaks are shut in "closed-mouth vocalization". This conclusion has been arrived at according to a review of the vocal data from bird and crocodile species by scientists from universities in Arizona, Texas, Utah and Canada.
"Looking at the distribution of closed-mouth vocalization in birds that are alive today could tell us how dinosaurs vocalized," Chad Eliason from The University of Texas Jackson School of Geosciences and the study's co-author said. "Our results show that closed-mouth vocalization has evolved at least 16 times in archosaurs, a group that includes birds, dinosaurs and crocodiles. Interestingly, only animals with a relatively large body size (about the size of a dove or larger) use closed-mouth vocalization behavior."
The research, published in Evolution, explained: "Closed-mouth vocalizations are rare in the small-bodied passerines. In light of these results and body size trends in nonavian dinosaurs, we suggest that the capacity for closed-mouth vocalization was present in at least some extinct nonavian dinosaurs. As in birds, this behavior may have been limited to sexually selected vocal displays, and hence would have co-occurred with open-mouthed vocalizations."
Further study is expected to integrate data gathered from fossils, experimental physiology, gene expression and sound modeling, so that sounds produced by extinct early avian species, as well as by those of their dinosaur ancestors can be understood.