For centuries, sharks have been shrouded in mystery, with many believing they lived in a world of silence. However, a recent discovery has rewritten what we know about these ancient predators. Scientists have made the first known recordings of active sound production by sharks, revealing that some species may not be as silent as thought.
Researchers at the University of Auckland’s Leigh Marine Laboratory studied the rig shark, a small, bottom-dwelling shark native to New Zealand. During routine hearing experiments, ten juvenile rig sharks produced distinct clicking sounds when handled underwater. The clicks were consistent and audible, suggesting that sharks may not be voiceless after all.
The clicks only occurred when the sharks were briefly handled and didn’t happen during feeding or rest. Most clicks happened in the first ten seconds of handling and dropped off after that. This suggests that the sounds may be a reaction to stress, potentially used as a defense mechanism or to confuse potential predators.
To understand how sharks make these sounds without sound-producing organs, researchers examined the cranial structure of the rig shark using microCT scans and detailed dissections. The teeth emerged as the most likely mechanism, suggesting that the snapping action of the jaws creates the broadband clicks observed in the study.
The purpose of the clicks remains uncertain, but comparisons with other fish species reveal similarities with predator-related sounds. This discovery also echoes recent findings in rays, which produce sharp broadband clicks when divers approach.
While not all sharks show this behavior, some species may be more sensitive to human presence or have varying sensitivity to stress. Further research is needed to pinpoint exactly how the sound is made and what it might mean for shark communication. The study has shifted our narrative, revealing that even sharks may have something to say – albeit in a way we’re still trying to understand.
Source: https://www.earth.com/news/some-sharks-make-sounds-despite-not-having-vocal-cords