What Did Dinosaurs Sound Like?

A Brief Foray into Paleoacoustics in Science and Film

by Niko Borish and Caroline Lee

Did Dinosaurs Roar?

When you think about dinosaurs as living animals, what do you think of? Many people imagine them as they are depicted in the Jurassic Park films – giant reptiles, clad in scales, generating reverberating roars that shake the screen. Although this image is certainly entertaining, research in recent years points to unexpected findings that are no less interesting. Evidence suggests that dinosaur vocalizations were not likely to have sounded like roars at all! We’ll explore what’s known about the real voices of dinosaurs with a paleontological source and an interview with an expert who has made relevant discoveries. We’ll also discuss how the sounds you hear in the Jurassic Park films were created!

Paleoacoustics and Dinosaur Vocalizations

We had a chance to interview Dr. Julia Clarke, a paleontologist at the University of Texas, to learn more about paleoacoustics (the study of sound associated with fossils) in non-avian dinosaurs and their evolutionary descendants, birds. In Antarctica in the mid-1990s, Vegavis iaai, an ancient bird dating to around 66 to 68 million years ago, was excavated. Dr. Clarke analyzed the fossil, and in 2013 found evidence that Vegavis had a vocal organ specific to birds, known as a syrinx. In extant (meaning alive today) bird species, the syrinx is responsible for all the vocalizations we identify as bird songs or calls. This means that Vegavis most likely honked (not unlike a goose), owing to an asymmetrical third segment in the syrinx. When we asked why it took about two decades to find the syrinx after the fossil’s original discovery, Dr. Clarke answered that “discovery is not just one moment.” She received the fossil for study in 2008. When she was about to return it in 2012, she went over its computed tomographic (CT) scan images again and noticed something new – a tiny structure that looked like a simple bone fragment or toe bone on the surface of the rock. It turned out to be the syrinx! Clarke and her coauthors noted that we still don’t know when the syrinx evolved because non-avian dinosaur fossils lack this structure. Vegavis is related to extant bird species, and despite searching, no earlier dinosaur syrinxes have so far been found.

Carnivorous dinosaurs are often pictured as chasing prey while letting out intimidating roars. Other new discoveries made from studies of extant birds indicate that this image is a misconception. Dr. Clarke explained that instead of open-mouthed roars, scientists theorize that many dinosaurs may have produced closed-mouth vocalizations. Animals produce closed-mouth vocalizations by inflating their esophagus (the tube that connects the throat and stomach) or tracheal pouches (pouches on their windpipe) while keeping their mouth closed, producing something comparable to a low-pitched swooshing, growling, or cooing sound. These closed-mouth vocalizations differ substantially from open-mouth vocalizations like bird calls. Think of closed-mouth vocalizations as being lower and more percussive, as opposed to bird calls, which are more varied in pitch and almost melodic. Modern examples of closed-mouth vocalizations include crocodilian growls and ostrich booms. As a result, scientists reasoned that many dinosaurs did not perform open-mouth vocalizations, but could have generated closed-mouth vocalizations instead. Although birds evolved from theropods (a group of dinosaurs characterized by, among other attributes, hollow bones and a bipedal stance), theropods likely did not have the ability to make complex sounds similar to those of extant songbirds.

Perhaps sadly, the exciting, blood-curdling roars in the Jurassic Park franchise are not scientifically accurate. Current evidence supports that Tyrannosaurus rex made closed-mouth vocalizations, but in the films, the Tyrannosaurus opens its mouth every time it roars. That begs the question: who or what voiced the Tyrannosaurus and other Jurassic Park dinosaurs? The majority of the sounds used to create the Tyrannosaurus sonic palette came from recordings of elephant bellows. Also used were crocodilian growls, roars from lions and tigers (but not bears), the sound of water coming up from a whale’s blowhole, and even growls from the sound producer’s dog. Some other animals’ sounds that were used to make different dinosaurs’ vocalizations include: hawing donkeys, neighing horses, growling tortoises, whistling dolphins, howling howler monkeys, oinking pigs, barking fennec foxes, and chirping birds! Most of these sounds were edited and pitched up or down to fit their roles.

Another popular misconception initiated by the Jurassic Park franchise was the concept of the “Velociraptor resonating chamber.” In Jurassic Park III, the protagonists search for a “Velociraptor resonating chamber” that allows them to communicate with the Velociraptor pack. However, the possibility of this structure was debunked by Dr. Clarke and Dr. Matt Lamanna, a paleontologist at Carnegie Museum of Natural History. The resonating chamber does not actually exist. If such a chamber existed, it would only amplify the sound (auditory vibrations that travel through the air) made by dinosaurs, not modify its timbre (the tone quality of a sound) or pitch (a measure of how high or low a sound is), which would not allow humans to imitate Velociraptor sounds as shown in the movie. In other words, it would not work like a giant duck call. Additionally, the way that scientists perceive closed-mouth vocalizations to function disproves the whole idea of a resonating chamber to begin with. This is because the organs involved in vocalization include either esophageal or tracheal pouches but no dedicated “resonating chamber.”

What non-avian dinosaurs really sounded like is an enigma currently being uncovered by teams of researchers like that led by Dr. Clarke. All in all, while the movies are certainly helpful for getting people interested in dinosaurs and paleontology, a logical next step is to schedule a visit to Carnegie Museum of Natural History to get the real facts!

We would like to extend a gargantuan thank-you to Dr. Julia Clarke and Dr. Matt Lamanna for generously offering expertise for our blog! Their help evolved our blog to the next level, and for that we are extremely grateful.

Niko Borish and Caroline Lee are Teen Volunteers in the Education Department. Museum employees, volunteers, and interns are encouraged to blog about their unique experiences and knowledge gained from working at the museum.

References

Analysis of fossilized Antarctic bird’s ‘voice box’ suggests dinosaurs couldn’t sing. (2016, October 12). National Science Foundation. Retrieved March 7, 2021, from https://www.nsf.gov/news/news_summ.jsp?cntn_id=189996

Clarke, J. (2016, July 16). New Research Debunks The Dinosaur’s Roar (Interview by L. Wertheimer) [Radio broadcast]. In Weekend Edition Saturday. National Public Radio. https://www.npr.org/2016/07/16/486279631/new-research-debunks-the-dinosaurs-roar

Riede, T., Eliason, C. M., Miller, E. H., Goller, F., & Clarke, J. A. (2016). Coos, booms, and hoots: The evolution of closed-mouth vocal behavior in birds. Evolution, 1734-1746. https://doi.org/10.1111/evo.12988

Taylor, D. (Host), & Nelson, A., & Clarke, J. (n.d.). Tyrannosaurus FX (No. 105) [Audio podcast episode]. In L. Battison (Producer), Twenty Thousand Hertz. Twenty Thousand Hertz. https://www.20k.org/episodes/tyrannosaurusfx

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