A PhD student researching shark hearing has discovered that rig sharks produce clicking sounds, marking the first documented case of a shark making noise.

Carolin Nieder was handling rig sharks during her study when she first heard the unexpected sounds. Nieder said she initially had no idea what they were.

“At first we had no idea what it was, because sharks were not supposed to make any sounds,” Nieder said. “I remember coming home and just thinking more and more about how weird those sounds were.”

The study, published in Royal Society Open Science, was led by Nieder under the supervision of Professor Craig Radford, an expert in marine bioacoustics.

The researchers suggested that the sounds may be produced by the forceful snapping of the shark’s flattened teeth. The rig shark, a small native species, inhabits shallow estuaries and coastal waters. It feeds on crabs and is preyed upon by larger sharks.

Radford said the discovery challenges the long-held assumption that sharks, rays, and skates do not make sounds.

“Reports of rays producing clicks in response to approaching divers had already cast doubt on this idea,” Radford said.

The scientists speculated that the rig’s clicks during handling might be a stress or startle response. Further research is needed to determine whether rig sharks produce clicks in natural conditions and whether the noises serve as an alarm or defence signal.

Fishes employ a variety of sound-producing mechanisms. Some species vibrate their swim bladder using drumming muscles, while others grind or snap hard structures like bones and teeth.

This discovery raises new questions about how sharks communicate and interact with their environment.