A Study Debunks a Persistent Myth About Sharks

If in space no one can hear you scream, new research reveals a very different situation in the waters of the globe where the well-known predators—sharks—swim.

Sharks less tough on paper than expected

Led by researchers from Florida Atlantic University, these studies involved the controlled diffusion of sounds and drone monitoring to assess the auditory abilities of sandbar sharks (Carcharhinus limbatus), inhabiting the clear, shallow waters of the southeast coast of Florida.

Unlike humans, who possess large external ears, the ears of sharks are reduced to modest openings connected to their internal auditory structure. At first glance, they might seem of limited usefulness in an aquatic environment, but it turns out that sounds propagate through water faster and farther than through air.

Consequently, the sharks can construct a genuine acoustic landscape of their surroundings, which helps them identify prey or dangers (predators, boats…). However, until now, it remained unknown precisely how far they could perceive such waves.

The experiment involved broadcasting sounds of varying frequencies using an underwater speaker. From the air, drones filmed the responses of C. limbatus swimming in the surrounding waters. It turned out that they perceived the different sound frequencies broadcast, with the exception of the reference one, at distances of up to 74 meters, the length of the Bayeux Tapestry.

A Surprise

As explained by Stephen Kajiura, the lead author of the new study, published in the journal Integrative Organismal Biology, the real surprise was the sharks’ ability to perceive sounds located beyond the near acoustic field, with markedly different wave patterns.

The next step will notably be to determine the sensory mechanisms that underlie it. At a time when noise pollution affects many marine species, such findings could contribute to improving their conservation.

To reassure those who imagine themselves frolicking in the water and attracting the attention of a great white, when they perceived these unusual sounds, the sharks quickly moved away in the opposite direction, making a Jaws outcome unlikely.