3 days Ago
Researchers document a rig shark's vocal capabilities in a University of Auckland experiment ...
More conducted between May 2021 and April 2022. Click. Click.
Click. Marine biologist Dr. Carolin Nieder, working on her Ph.
D. at the University of Auckland in New Zealand, was stumped. "When I first heard the sound, I thought [.
..] they sound like electric sparks," Nieder, who is now at the Woods Hole Oceanographic Institution, said.
Her project was focused the hearing abilities of several shark species that called New Zealand home, and this sound shouldn’t be there. “I kind of knew that sharks are silent, that they don’t make any active sounds. So I kind of it didn’t register [the click] at first, but then it kept happening.
” Click. Click. Click.
“I remember coming home and just thinking more and more about how weird those sounds were," she continued. For decades, sharks have been seen as silent hunters, slipping through the water undetected. That is, until now.
Nieder and a team of researchers have recorded a small shark species producing clicking sounds, marking the first known instance of a shark actively making noise. The findings challenge long-standing assumptions about these fish and raise new questions about their behavior and communication. Rig sharks ( Mustelus lenticulatus ) are found in coastal waters around New Zealand and weren’t supposed to make sounds.
Yet, when Nieder handled them between experiments, they began to...
well, sort of crackle. At first, she dismissed the noise. Sharks, unlike many fish that use their swim bladders to produce sound, lack this organ.
So where was the noise coming from? Unlike the pointed teeth of many sharks, rigs have flattened, overlapping teeth adapted for crushing ...
More crabs and shellfish. The team suspects that the clicks are produced when the sharks snap their jaws together, similar to how some terrestrial animals, like snapping shrimp, make noise. To confirm the source, Nieder and her colleagues placed ten juvenile rig sharks in tanks equipped with underwater microphones.
Each shark was held for 20 seconds while researchers recorded the sounds they made. Every single one produced short, high-frequency clicks, primarily in the first ten seconds of handling. This suggests the sounds were a reaction to being startled rather than an attempt at communication.
The clicks were also beyond the sharks’ own hearing range but within the range of some of their predators, like toothed whales. Some fish, like cod , are known to make similar sounds to startle predators; could the rig sharks be using the clicks as a defensive mechanism? Possibly. The clicks primarily fall within the 2,400 to 18,500 Hz range, which is far above the shark’s hearing range of 150 to 800 Hz, but the initial pulse occurs at a lower frequency, suggesting the sharks might be able to detect the sounds they produce.
But that didn’t answer another big question: without a swim bladder, how were these sharks producing sound? To investigate, the researchers created 3D reconstructions of the rigs’ jaws and teeth. Unlike the pointed teeth of many sharks, this species has flattened, overlapping teeth adapted for crushing crabs and shellfish. The team suspects that the clicks are produced when the sharks snap their jaws together, similar to how some other animals (like snapping shrimp) make noise.
This study isn’t the first to suggest that cartilaginous fish can produce noise. Recent research has documented stingrays and skates making clicking sounds when approached by divers in the Mediterranean , Indonesia, and Australia . Given that sharks and rays diverged over 200 million years ago, sound production may be an ancient ability shared by many species.
But while these findings present strong evidence that some sharks can make sounds, the question remains whether rig sharks do this in natural settings or only when disturbed. And if they did click in the wild, why? Nieder hopes to conduct future studies on rigs and other shark species in the wild to better understand what triggers the sounds..
