Blacktip Sharks Hear Sound From More Than 200 Feet Away, Study Finds

Every winter, hundreds of blacktip sharks gather just off the Florida coast, close enough to shore that beachgoers rarely notice them. Researchers recently found these sharks can hear a sound from roughly two-thirds the length of a football field away, then whip around instantly and swim off in the opposite direction. That single observation is now forcing a rethink of how well sharks can actually hear.

For years, scientists believed sharks could only pick up sound at close range, a zone called the “near field” where water particles physically bounce around. Farther out, in the “far field,” pressure waves take over, and picking up that pressure is generally thought to require a gas-filled swim bladder. Sharks don’t have one, so researchers assumed their hearing simply couldn’t reach that far. A new study of wild blacktip sharks off Southeast Florida, published in the journal Integrative Organismal Biology, suggests that assumption was wrong.

Researchers used an underwater speaker and a flying drone to test how blacktip sharks responded to different pulsing sounds. Sharks reacted to sounds from at least 62 meters away, or roughly 203 feet, and 71.5 percent of their 165 recorded responses happened in the acoustic far field. In plain terms, these sharks were hearing and reacting to sound far outside the range scientists thought possible.

How Researchers Tested Blacktip Shark Hearing in the Wild

Blacktip sharks gather in large numbers off Palm Beach, Florida, every winter, making them an easy and predictable subject to study in shallow, clear water. Researchers anchored a boat near known shark gathering spots near the Jupiter, Palm Beach, and Pompano Beach inlets, then lowered an underwater speaker about three feet below the surface and let it trail roughly 40 to 60 feet behind the boat.

Four sounds played through the speaker: three pulsing tones at different pitches (roughly 100 to 200 hertz, 200 to 400 hertz, and 400 to 800 hertz) and a high-pitched control sound at 10,000 hertz that sharks are known not to hear. Underwater microphones placed at various distances measured exactly how loud each sound was as it traveled through the water, letting the team calculate how the sound faded the farther it went.

Instead of watching from the boat, which could scare off the sharks or block a clear view, the team flew a drone overhead at about 130 to 165 feet, high enough that the sharks couldn’t detect it. The drone camera looked straight down, capturing both the sharks and the speaker in the same shot. A floating light box above the speaker flashed whenever a sound played, giving the drone operator a visual cue to match footage to each test sound. Researchers later measured each shark’s exact distance from the speaker using the boat’s known length as a ruler, then tracked the angle of the shark’s swimming path before and after the sound played.

What the Footage Showed

A reaction was unmistakable on video: a shark swimming calmly would suddenly whip around, turning anywhere from 20 to 160 degrees away from the speaker, then swim off fast. That reaction showed up again and again. Sharks responded to the lowest pitch band about 82 percent of the time, to the middle pitch band about 87 percent of the time, and to the highest pitch band about 71 percent of the time. Not a single shark reacted to the high-pitched control sound in any of those control tests, suggesting the sharks responded to the specific test sounds rather than to any noise or simply the speaker’s presence.

Average reaction distances ranged from about 98 feet to 134 feet, depending on pitch, with some individual sharks reacting from as far as 243 feet. When researchers compared those distances to where the near field supposedly ends for each sound’s pitch, they found that most reactions happened well past that line, out in the far field.

Loudness mattered too, and it mattered differently depending on pitch. The lowest pitch sound only needed to be about 16 decibels louder than background ocean noise to trigger a reaction. The highest pitch sound needed to be roughly 45 decibels louder. That pattern matches earlier research showing sharks are most sensitive to low, deep sounds, similar to the rumble a struggling fish might make.

Why This Changes the Conversation Around Shark Hearing

This finding matters beyond simple curiosity about how sharks sense the world. Sound travels fast and far underwater, much farther than smell or sight in murky water, so an animal that can detect and react to sound at a distance has a real edge in the ocean, whether it’s avoiding danger or homing in on a meal. Knowing that blacktip sharks can pick up specific pulsing sounds from well over 100 feet away, and reliably swim away from them, gives anyone designing sound-based tools meant to keep sharks away from swimmers, divers, or fishing gear something concrete to work with.

Researchers still aren’t sure exactly how sharks manage to sense sound that far away without a swim bladder to help. One idea is that sharks may pick up on subtle water movement, called particle motion, that lingers even in the far field, though the exact biology behind it remains an open question.

What’s no longer in question is the behavior itself. Blacktip sharks in this study consistently and dramatically reacted to underwater sound from distances that should have been beyond a shark’s hearing range. That alone is reason to rethink how attuned these animals really are to the sounds moving through the water around them.