Scientists from Florida Atlantic University conducted a study examining how far blacktip sharks can detect underwater sounds and whether they can determine the direction of those sounds. The research, published in Integrative Organismal Biology, utilized an underwater speaker, a drone, and wild sharks in their natural coastal habitat to gather data on shark hearing capabilities.
The study took place in shallow coastal waters near Palm Beach County, where blacktip sharks congregate predictably throughout the year. Researchers positioned an underwater speaker at varying distances from free-swimming sharks and played three groups of low-frequency sounds ranging from 100 to 800 Hertz, along with a 10 kiloHertz control sound outside the known shark hearing range. A drone positioned 40 to 50 meters above the water recorded the sharks’ movements and behavioral responses as the sounds were played.
The findings revealed that sharks detected low-frequency sounds from distances up to 74 meters, or approximately 243 feet. Most significantly, the sharks did not merely detect the presence of sound; they demonstrated the ability to determine its direction by making rapid turns away from the speaker. Over 70 percent of recorded responses occurred in the acoustic far field, indicating that sharks can sense and respond to distant sounds even when they rely on detecting particle motion rather than sound pressure.
The research is particularly notable because sharks lack the gas-filled swim bladder present in many bony fish, which helps those species detect sound pressure. Instead, sharks depend largely on their inner ear structures, including a specialized sensory organ called the macula neglecta, to detect vibrations and motion generated by sound traveling through water. The study demonstrates why conducting hearing experiments in open ocean environments proves more effective than laboratory tank settings, where sound reflections off walls create complex and confusing acoustic patterns that obscure natural responses.
Researchers indicated that these findings suggest sound provides sharks with valuable information about distant events and potential prey or threats located hundreds of feet away, long before they become visible. The team plans to continue investigating how shark sensory systems specifically detect and process these distant acoustic signals.
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