'Silent Killers' Sharks Break Their Silence Underwater, Caught Making Sounds for the First Time Ever

In the deep, dark abyss of the ocean, where lights barely reach and silence reigns, sharks have long been considered the ultimate stealth predators. Their quiet, swift moments and lack of vocalization have cemented their reputation as silent killers. Unlike whales or dolphins, which communicate through an array of clicks and whistles, sharks have been thought to rely completely on their sharp senses, from detecting electric fields to sensing the faintest vibrations in the water, stated Science Alert. However, an important point to note is that what if this assumption was wrong? What if sharks have been making sounds all along, and surprisingly, we just never noticed?

In a stunning discovery, scientists have, for the first time, recorded sharks consistently making noise. The unexpected finding has stunned marine biologists challenging everything we thought we knew about these ancient creatures. Researchers from the Woods Hole Oceanographic Institution and the University of Auckland recorded the sounds made by the rig shark (Mustelus lenticulatus) in controlled lab conditions. These sharks emitted quick clicking noises when handled, a phenomenon never recorded before in any shark species. Carolin Nieder shared, "I was very surprised…I was under the assumption that sharks don't make sounds," stated Science Alert.

Intriguingly, the discovery opens up a new field of research into how sharks might communicate, defend themselves, or interact with their surroundings. The clicks recorded were short, lasting around 48 milliseconds each, and ranged from 2.4 to 18.5 kilohertz. Nieder noted, "Back in 2021, I used behavioral training experiments combining food and sound, which also included some handling. During these experiments, I happened to notice that one of the shark species made a clicking noise when being handled underwater…At first, we thought it might be a strange artifact. However, with time, as the animals got used to the daily experimental protocol, they then stopped making the clicks all together, as if they got used to being in captivity and the experimental routine. This led us to consider that maybe we are observing a sound-making behavior rather than a strange artifact," stated Smithsonian Magazine.

When the researchers handled the sharks for short periods, the animals produced the clicking sounds, but intriguingly, they remained silent when swimming freely or feeding. However, the frequency of the clicks decreased as the sharks became versed in the handlers, indicating that the sounds could be a distress signal. Researchers noted, "Within the limits of the available data, the broadband frequency range and short duration of the rig clicks suggest the involvement of teeth snapped during rapid mouth closure for sound production…However, additional investigations will be necessary to test this hypothesis," stated Science Alert.

However, more research is needed to confirm this theory. Even more interesting is whether these sharks can hear the sounds they produce. Neider exclaimed, "One possibility could be that the sounds are a form of a startle response (in the wild perhaps in response to an attack by a larger shark or marine mammal)...Scott Tindale (Tindale Marine Charitable Trust), who dedicates his life to tagging sharks and other fish all around New Zealand and Australia and who happened to hear similar clicks rigs in the wild, even before I noticed them, thought that perhaps the rigs try to imitate snapping shrimps (part of their diet) to lure them out of their burrows in the sediment to then attack them. I think that is a very interesting theory as well," stated Science Alert.