First shark sound recordings captured by researchers, study shows
The first-ever sounds of sharks have been captured by researchers, according to a new study published in the journal Royal Society Open Science.
The study, published Wednesday, found that the rig shark -- also known as the spotted estuary smoothhound -- produces clicking sounds when handled, according to the study.
"Sharks are maybe not as silent as we thought," Carolin Nieder, marine biologist at Woods Hole Oceanographic Institution and lead author of the study, told ABC News.
Nieder said the sounds were "discovered by accident" as she was conducting another study analyzing the hearing capabilities of sharks during her doctorate program at the University of Auckland in New Zealand.
"I had never considered that any of the sharks I was studying could make any sort of sound. I was under the assumption that sharks are silent fish, so they wouldn't make any active sounds," she said.
Nieder caught seven rig sharks in the Kaipara Harbour in New Zealand, obtained three more from a local commercial fisherman and housed them in a marine laboratory in "circular flow-through holding tanks," the study said.
After acclimating for at least a week, the sharks were transferred from their holding tank into an experimental tank, where the handling took place, the study said.
During the handling, the rigs were "opportunistically observed to produce clicking sounds underwater."
On average, the sharks produced "nine clicks during handling underwater" over the course of 20 seconds, with significantly more clicks during the preliminary 10 seconds, the study said.
The overall click duration was only 48 milliseconds, the study said.
Twenty-five percent of the clicks occurred when the sharks reacted with "vigorous bending of the head and body from side to side," about 70% occurred with "calm swaying," and 5% of clicks occurred in "the absence of any obvious body movements," the study said.
The initial handling "triggers a stress to startle response, resulting in increased click activity" and as the sharks become more accustomed to the handling, "the behavioral response likely diminishes, leading to fewer clicks over time," the study said.
"The rig is a smaller shark. It's vulnerable to predation," Nieder said. "Maybe if a small shark like this gets attacked, maybe these clicks can disorient the predator for just a split second to escape."
Nieder told ABC News the rig shark is able to produce this clicking sound due to its flat teeth, which differ from the teeth other sharks possess.
Neil Hammerschlag, president of Atlantic Shark Expeditions who was not part of this study, said he has "long thought they must have some way to communicate through sound."
"The idea that some sharks are making sounds is exciting because to me, that suggests they could use that as a form of communication. This opens up an avenue for future research," Hammerschlag told ABC News.
Nieder hopes this initial observation will inspire others to dive into research surrounding sharks and that more people will be "curious about current notions and to keep listening to other animals and species that are deemed silent."
