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According to research by scientists, large dinosaurs could only hear low-frequency sounds. Their hearing was better suited to loud noises like the crash of a heavy object than to sharp sounds such as a bird’s screech or a whistle. As a result, dinosaurs like Brachiosaurus and Allosaurus could hear the footsteps of other dinosaurs from a distance, but could hardly hear the cries of prey caught in their grasp—if they heard them at all, it was very faint.
The idea about the limits of dinosaur hearing has originated from studies on the hearing ability of birds. After all, due to evolution, birds are the closest living relatives of dinosaurs. According to Robert Dooling, a hearing specialist at the University of Maryland, we now know quite a bit about how birds hear. He says, “Large birds hear low-frequency sounds better, while small birds hear high-frequency sounds better.”
In his latest joint study with two German scientists, Dooling claims that this pattern of hearing holds true from tiny songbirds to the massive, 68-metric-ton dinosaurs like Brachiosaurus. The reason is that the internal ear structure of birds, dinosaurs, crocodiles, and almost all archosaur animals is very similar. Dooling explains, “This is possible because the auditory organs of birds and dinosaurs are essentially different-sized versions of the same model.” He also says, “The inner part of a bird’s ear, mainly known as the basilar papilla, is closely related to the bird’s overall body size.”
Robert Dooling and his two German colleagues conducted long-term research on more than thirty bird species, establishing a relationship among their body mass, the length of the basilar papilla, and their hearing range. Dooling claims that with this relationship, one can almost perfectly determine the hearing limits of most bird species based solely on body size.
Using this same method, the hearing limits of dinosaurs can also be determined, if their physical structure—specifically the length of their basilar papilla—is known. Dooling’s team used fossils of Brachiosaurus, Allosaurus, and Archaeopteryx to estimate the length of their basilar papilla. They found that the ratio between body size and basilar papilla length in these dinosaurs and in any modern bird species is basically the same. Therefore, Dooling’s research suggests that their hearing range should also be proportionally similar.
This research essentially means that while humans and most animals today can hear a certain frequency range, prehistoric dinosaurs could not hear those same frequencies. In Dooling’s words, “You shouldn’t expect a dinosaur from yesterday to hear the call of a bird from today.” This raises the question: how did dinosaurs communicate with each other? Scientists believe their vocal cords were likely adapted to their hearing abilities, meaning that they probably produced low-frequency sounds.
Robert Dooling and his fellow researchers presented these findings last week at the annual conference of the Acoustical Society of America, held in Salt Lake City, Utah, USA.
With this discovery, perhaps more new information will emerge in the future about extinct dinosaurs and their ancient environments.
Adapted from Scott Norris’s “Big Dinosaurs Heard Only Low Pitch Sounds, Experts Suggest” at National Geographic News (http://news.nationalgeographic.com/).
Mozammel Hosain Toha
+218 92 7058964
Sirte – Libya
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