Can sharks make sounds? Scientists uncover the first evidence of it
Sharks-the underwater rulers are one of the most enigmatic yet deadly creatures that terrify not only the general public but also oceanographers. With their intelligent skills and dominating size, sharks glide through the waves with utmost confidence and an aura of terror.
These deep-water hunters have always been considered silent and sharp, as they lack swim bladders, the organs that help fishes make sound. However, a new study made at the University of Auckland’s Leigh Marine Laboratory has completely altered these beliefs by revealing that these aquatic creatures make very distinct sounds.
In the study published in the Royal Society Open Science, scientists shared the first-ever known recordings of sharks producing active sounds while moving underwater.
Ten rig sharks (Mustelus lenticulatus), a small bottom-dwelling shark native to New Zealand were studied during routine hearing experiments and it was seen that they made clicking sounds when underwater. The sounds were not random splashes or incidental noises, they were consistent, sharp click sounds.
Do the sharks produce clicking sounds?
These clicking sounds were produced when the sharks were briefly handled, with most clicks appearing in the first ten seconds and stopping after that. This suggested that the sounds were potentially a reaction to stress when they were either trying to defend themselves or confuse the potential predators.
The researchers counted an average of nine clicks per shark in a 20-second window. About three-quarters of those clicks were short and single-pulse bursts, whereas the rest were double-pulse clicks made in rapid succession. While some clicks coincided with physical movements such as swaying or bending, others came with no visible movement.
How do sharks produce sounds?
Image credits: Canva
With no organs to help them make sounds and a lack of vocal cords, how do sharks produce the clicking sounds? Researchers used micro CT scans and detailed dissections to study the cranial structure of these sharks and found that teeth are their sound-producing mechanisms for them.
Rig sharks have blunt, interlocking teeth arranged like flat plates which snap together during rapid jaw movements that last for an average of 48 milliseconds with frequencies between 2.4 and 18.5 kHz.
Do other species make similar sounds?
As per the study, the rig sharks made these sounds only when in an uncomfortable territory and not when they were freely swimming. Such is also the case with teleost fishes, like cod and piranhas, that emit clicks when approached by predators. Since 2022, several studies have also reported click sounds in stingrays, skates, mangrove whip rays and blonde rays.
However, it should be noted that not all sharks make these sounds. Researchers also tested the theory on three dusky smoothhounds, which are close relatives of the rig sharks, only to see that they produce no sounds under stressful situations.
