The classic image of a dinosaur shows it with its head tilted back, bellowing a ferocious roar. Yet in reality, we don’t really know what noises the beasts actually made. Now a new study looking into dinosaur vocalizations has revealed that some dinosaurs might have been mumblers, and cooed with their mouth shut rather than bellowed. Think giant dove, only with gnashing teeth.
To investigate whether or not dinosaurs may have cooed or rumbled, the researchers turned to their living decedents still flocking around us. They looked at more than 200 different species of bird and assessed which ones were able to perform “close-mouth vocalizations”. Out of these, they identified 52 species that made noises without opening their beaks, and then plotted where on the evolutionary tree they sat.
What they found was that the ability to make squeaks and squawks without opening the bill has actually evolved separately more than 16 times in the group that contains birds and crocodiles known as Archosaurs. Crucially, this group also contains their larger, more ferocious relatives, the dinosaurs. This means that it is quite likely that at least some of the creatures that are often depicted as roaring and shouting were really making far more understated coos and chirrups.
What this latest piece of research has also found is that close-mouth vocalizations are more common in the relatively larger species of birds, from about the size of a dove and above. This is due to the physiology and physics of how the sounds are made. “The inflation of an elastic cavity could present a size-dependent challenge,” explains Tobias Riede, first author of the study published in Evolution. “The lung pressure required to inflate a cavity depends on the tension in the wall of the cavity, and this tension increases for smaller body sizes.”
As dinosaurs tended to be much larger than modern birds and crocodiles, this means that it was even more likely that dinosaurs were muttering to each other with their mouths shut. Looking at the situations in which modern birds tend to coo and rumble, the researchers noticed that they tended to be in situations to do with finding love and territory defense, while at all other times they then would usually switch to more conventional noises. So perhaps dinosaur sweet talk was more of a sweet mumble.
But if you’re concerned that this new theory may have diminished slightly from the terrifying reputation of the dinosaurs, then you may not have heard the unsettling and fairly creepy notes that can be heard echoing off the forested hills of New Zealand as male Kakapos call for mates, or the unnerving guttural roars of the cassowary ringing through the Australian rainforest.
