Sharks May Not Be Silent After All!
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Sharks have always been considered silent swimmers. Unlike most fish, these top ocean predators lack sound-producing organs. But recent research suggests this might not be true for all sharks. At least one species produces noise, challenging our understanding of these stealthy hunters.
Carolin Nieder stumbled upon this discovery accidentally while studying rig sharks at the University of Auckland in New Zealand. The marine biologist noticed the sharks would make clicking noises when she handled the animals between lab tests.
"When I first heard the sound, I thought they sounded like electric sparks," Nieder said.
Curious to know more, Nieder and her team conducted an extensive study of ten juvenile rig sharks in a lab from May 2021 to April 2022. Each day, the researchers moved the shark individually between tanks fitted with recording devices. Each shark was held for 20 seconds. As the animals were being moved, they made short clicking sounds.
Each click lasted just 48 milliseconds. But it was loud, reaching over 152 decibels. This is louder than a balloon popping near your ear! The sounds also spanned a wide range of frequencies, from 2.4 to 18.5 Kilohertz. Most clicks occurred during the first ten seconds of handling. Over time, the sharks stopped making noise entirely.
"As the animals got used to the daily experimental protocol, they then stopped making the clicks altogether, as if they got used to being in captivity and the experimental routine,” Nieder told CNN. “This led us to consider that maybe we are observing a sound-making behavior rather than a strange artifact."
Since the sharks have no sound-producing organs, the researchers believe the clicks come from their strong, interlocking teeth snapping together.
Interestingly, the sounds occur at frequencies far above the rig shark's typical hearing range, which tops out around 800 Hertz. That suggests the clicks are not meant for communication. Instead, they might serve as a distress signal – a reaction to being handled during the experiment. The clicks could also be a defense mechanism. Several predators of rig sharks — like toothed whales — can hear these higher frequencies.
Nieder and her team published their findings in the journal Royal Society Open Science on March 26, 2025. They plan to continue their research to better understand why rig sharks make clicking sounds. They also want to investigate whether other shark species make similar noises.
Rig sharks, also known as spotted smooth-hounds, are small, slender sharks found around New Zealand and southern Australia. They get their name from the faint white spots along their gray bodies. Unlike many sharks, rigs have flat teeth for crushing crabs, shellfish, and other bottom-dwelling prey. They often swim in shallow waters and are harmless to humans.
Resources: Smithsonianmag.com, CNN.com, NPR.com
