Shark species recorded making sounds underwater for the first time
By environment reporter Peter de Kruijff
ABC Science
Topic:Marine Biology
16m ago16 minutes agoWed 26 Mar 2025 at 12:05am
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In short:
A common species of shark in New Zealand has been recorded making clicking sounds underwater.
Researchers hypothesise that the noise comes from the spotted estuary smooth-hound forcefully snapping its teeth.
What's next?
Further studies are required to understand why the shark makes the sound. Scientists are also keen to investigate if there could be more shark species making underwater noises.
The sea is a symphony of sounds from whale song to the guttural thumps and groans of a fish "drumming" an internal organ.
But marine scientists have long thought that sharks, a group containing more than 500 species, did not intentionally make noise underwater.
Some fish contract muscles to vibrate their swim bladder, a gas-filled body part that regulates buoyancy, to communicate but sharks do not possess the same organ.
Generally sharks, as predators, are built for silence with their skin textured in a way that reduces sound created by their movements.
But a new study in the Royal Society Open Science suggests a common New Zealand species could be making sounds on purpose, with its teeth.
A small grey shark with lightly-coloured beige spots on its body curled up in a large upturned human hand.
Spotted estuary smooth-hounds grow 70 to 150 centimetres in size and are predated on by larger species. (iNaturalist: Peter Langlands, spotted estuary smooth-hound, CC BY-NC 4.0)
Lead author and bioacoustician Carolin Nieder, from the Woods Hole Oceanographic Institution, didn't initially recognise what she was hearing when a shark started to "click".
"When I first heard the sound, I thought ... they sound like electric sparks," Dr Nieder said.
"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."
The clicking was coming from a spotted estuary smooth-hound (Mustelus lenticulatus) that Dr Nieder was testing for its hearing ability.
The species, which grows 70 to 150 centimetres in size, is found throughout New Zealand waters and is a common sight on fish and chip shop menus as a "lemon shark".
Other names for the shark in NZ include rig, spotted dogfish, gummy shark or the Māori words kapetā, mangō and pioke.
The clicking behaviour has been described in the new study as the first documented case of a shark deliberately making sound underwater.
Australian swell sharks and draughtboard sharks have been heard barking like a dog when taken out of the water.
A mottled army camouflaged-looking flat shark swims over a weedy seabed.
Draughtboard shark (Cephaloscyllium laticeps) inflate their stomach to look bigger, but when this is done out of the ocean they can sound like a barking dog. (iNaturalist: Brayden Thrower, draughtboard shark, CC BY-NC 4.0)
This is thought to be from a release of air because of a defence mechanism, where they puff up in size when threatened. But when the draughtboard shark does the same action while submerged in natural settings, no sound is produced.
Dr Nieder said the clicking started as the smooth-hounds were handled and seemed to be louder underwater than when taken out.
She said it was possible the sound was a weird evolutionary artefact that only occurred in captivity.
"Maybe it just makes clicks every once and a while, that's a really fair argument," she said.
"I think from my observation I can probably 99 per cent say I don't think so.
"The hypothesis that I had was that clicks are kind of a way to startle predator attacks."
A woman in a red dress with white flowers sitting in front of a beige wall with a wooden blue eagle ray silhoutte image behind.
Woods Hole Oceanographic Institution bioacoustician Carolin Nieder. (Supplied: Carolin Nieder)
Dr Nieder said NZ fisher and researcher Scott Tinsdale had also heard the smooth-hound clicking in the wild, but he thought it might be trying to imitate prey like shrimp.
As to whether the shark can hear it's own clicks, Dr Neider is not sure. The main frequency of the clicks is in the 2,400 to 18,500 Hz range, well above the shark's hearing range of 150 to 800 hertz. However, the initial pulse is in a lower range making it possible the species can detect the sound it makes.
How does a shark click?
Since Dr Nieder's research had focused on shark hearing, she did not have the funds to delve far into the mechanisms behind the clicking.
But study co-author, Eric Parmentier from the University of Liège, thinks the sound could come from the forceful snapping together of the small shark's flat plate-like teeth.
A zoomed in diagonal upper jaw with five rows of overlapping clam-shaped teeth visible.
The forceful snapping of the spotted estuary smooth-hound's plated teeth has been suggested as the source of an underwater clicking sound. (Supplied: Royal Society Open Science)
Curtin University bioacoustician Robert McCauley, who was not involved in the study, said a similar mechanism was common in other fish.
"Trevally, are well known to commonly make this type of sound where they gnash their pharyngeal plates — plates they grind up hard prey with — together to make rasping noises," he said.
Professor McCauley also noted that fish acoustics is an emerging area of knowledge.
"Our understanding of fish sound has changed as it's now becoming clearer that fish generate a host of complex sounds," he said.
"[They] can be very vocal at times, dominating sea noise in some places for many hours at a time, and they do so for a range of complex behavioural reasons."
Lachlan Fetterplace, a Swedish University of Agricultural Sciences marine ecologist who was not involved in the study, said the research was interesting but thought a more focused investigation was needed to determine the sound source in the shark.
The big question, he said, was whether sharks clicked in the wild, and if they did, why?
Other recent research into rays suggests a similar clicking behaviour could be a threat response.
Dr Fetterplace lead a study that observed wild clicking by the mangrove whipray (Urogymnus granulatus) and the broad cowtail stingray (Pastinachus ater) when approached by divers.
A brown stingray with a whip-like thin tail in brown water an a sandy stingray with a cow-like tail in beach shallows.
The mangrove whipray (Urogymnus granulatus) and the broad cowtail stingray (Pastinachus ater) have been observed making clicking noises. (iNaturalist: Asaph Whelan, Mangrove whipray, CC BY-NC 4.0; Searobson, Broad cowtail stingray, CC BY-NC 4.0)
He said the idea that elasmobranchs — sharks and rays — make sounds has been getting more attention in recent years.
"It just goes to show, once again, how much we still don't know about the marine world," Dr Fetterplace said.
"I wouldn't be surprised if more examples of elasmobranchs actively producing sound emerge over the next few years."
Dr Neider also thinks there may be more types of sharks making sounds, but encourages people who encounter them to keep a respectful distance and not aggravate them for a response.
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Posted16m ago16 minutes agoWed 26 Mar 2025 at 12:05am, updated14m ago14 minutes agoWed 26 Mar 2025 at 12:06am
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