Scientists at Florida Atlantic University conducted a study examining the hearing capabilities of blacktip sharks in their natural coastal habitat. The research, published in Integrative Organismal Biology, used underwater speakers, drones, and wild sharks to investigate how far these animals could detect sounds and whether they could determine the direction of acoustic sources.
The experiment took place in shallow coastal waters off Palm Beach County, where blacktip sharks gather in predictable numbers. Researchers positioned an underwater speaker up to 19 meters from an anchored boat and played low-frequency sounds across three ranges: 100 to 200 Hertz, 200 to 400 Hertz, and 400 to 800 Hertz. A control sound at 10 kiloHertz, which falls outside the known hearing range of sharks, was also used. Rather than attempting to attract the sharks, the team played sounds at volumes designed to trigger a startle response. A drone positioned 40 to 50 meters above the water recorded the sharks’ movements and reactions to the acoustic stimuli.
The results demonstrated that blacktip sharks detected low-frequency sounds from distances up to 74 meters, equivalent to 243 feet. Beyond simply detecting these sounds, the sharks frequently made rapid directional turns away from the speaker, indicating they could determine where the sound originated. More than 70 percent of recorded responses occurred in the acoustic far field, where sound behaves distinctly from its behavior closer to the source. The sharks proved most sensitive to lower frequencies, detecting these sounds from greater distances and at lower volume levels.
This finding is particularly significant because sharks lack the gas-filled swim bladder present in many bony fish, which assists those species in detecting sound pressure. Instead, sharks rely primarily on their inner ears, including a specialized sensory structure called the macula neglecta that may help them detect motion and vibrations. The ocean environment allowed researchers to observe natural shark responses in ways that laboratory settings cannot replicate, as sound reflects off tank walls and creates complex acoustic patterns that obscure interpretation.
The research suggests that sound provides sharks with valuable information about distant events and potential prey or threats hundreds of feet away, well before visual detection becomes possible. Scientists indicated they plan to conduct further investigation into how shark sensory systems detect and process acoustic signals at such considerable distances.
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