Stingrays have been documented making strange clicking sounds in the wild by scientists.

at the Swedish University of Agricultural Sciences and his colleagues have recorded individuals of two stingray species, the mangrove whipray (Urogymnus granulatus) and the cowtail stingray (Pastinachus ater), making the noises.

Stingrays, which are cartilaginous fish like sharks, are generally considered to be silent, but there have been a few anecdotal reports of them making noises under or .

So Fetterplace and his colleagues set out to investigate the phenomenon in oceans off the coast of Indonesia and Australia. The team managed to record mangrove whipray and cowtail stingray individuals making clicking sounds for a minute or two as a diver swam in towards them.

“We didn’t think that stingrays had the anatomy to make sounds,” says Fetterplace. “It’s kind of amazing because it shows that there are so many things in the ocean we don’t actually know.”

Stingrays have recently been shown to make but Fetterplace says the noises that his team have recorded are unlikely to be related to eating. “We didn’t see any evidence that they were chewing food,” he says. “Also, there’s a pattern in the sound with a constant beat going through it – which you don’t really expect in chewing sounds.”

It is unclear why the stingrays make the sounds. “My educated guess would be that they’re doing it as a warning,” says Fetterplace. “It could be used to physically startle something like a shark.”

“They might also be communicating to other rays that there’s danger,” he says.

“Although there has been some anecdotal evidence before this paper, it is the first one to actually present a recorded sound and some acoustic information,” says at the University of Exeter, UK. “I hope it will encourage researchers to focus on the acoustic ecology of these animals.”

The phenomenon may not have been more widely observed because stingrays only make the clicking sound rarely or maybe only certain species of stingray can make them, says Fetterplace.

He says people have already reached out to him to say they have heard stingrays make similar sounds and some have video footage. He plans to collate and analyse these reports. “If you have an example of stingrays making sounds – please send it to us,” he says.

But divers shouldn’t seek out stingrays to hear these noises, he says. “Stingrays are not aggressive unless they’re threatened. But if they are threatened, they have the potential to hurt you.”

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FIFTY years ago, people started dreaming of mining the deep seabed. Since then, those dreams have turned into a dystopian nightmare as scientists have found diverse, interconnected ecosystems at the bottom of the ocean and realised that mining them risks upsetting the health and functioning of our planet.

We have yet to start deep-sea mining, so this dystopia is just one version of the future, but it is one that may soon get the green light. Countries such as all have their sights set on the metals inside coal-sized nodules scattered across a vast abyssal plain, called the Clarion Clipperton Zone, 5000 metres underwater in the Pacific Ocean.

But turbocharging things is the Pacific island state of Nauru, which has used a controversial provision in international law to declare that its seabed-mining contractor, a subsidiary of Canadian-owned The Metals Company, intends to apply for a mining permit. The vague provision means that in two years’ time the International Seabed Authority shall “provisionally approve” Nauru’s nodule mine, which would operate according to the environmental regulations in place by then – which could be none. These are currently being discussed and are nowhere near ready.

If seabed mining were to go ahead, it could unleash an environmental disaster. Nodule mines could wipe out unique species and populations. Sediment plumes could choke animals, including those living far from the mines. Mining wastewater could pollute deep open waters. From tardigrades to tuna, octopuses, corals and whale sharks, nodule mining could harm a huge array of ocean life.

Nauru’s mine could be quickly followed by dozens more run by other countries and corporations, impacting thousands of square kilometres of seabed every year for decades. What’s more, it could pave the way for mining giant underwater mountains and hydrothermal vents, which are home to their own astonishing and little-known ecosystems.

Besides the immediate destruction, deep-sea mining could have far wider impacts, disrupting climate regulation, nutrient cycling and long-term storage of carbon in the ocean. And if pending environmental catastrophe isn’t alarming enough, mining could damage ecosystems that contain understudied chemicals with huge potential for new medicines.

However, deep-sea mining isn’t inevitable. That is why I have joined hundreds of other scientists and policy experts in calling for a global moratorium. Our outlines a case for a pause on mining until we understand what the full impacts would be, and is open for additional signatures from anyone who wishes to show their support.

Achieving such a move before the two-year period is up will be challenging, but we are optimistic it can happen. A promising avenue looks to be through the UN General Assembly, which has precedent. Its non-binding resolution on high seas drift netting led to a moratorium on this fishing technique, which kills huge numbers of dolphins, whales, sea turtles and seabirds. An equivalent UN resolution for a seabed-mining moratorium could also encompass a wider mining strategy to responsibly meet the demand for minerals needed by the rise in green technologies.

Momentum for a moratorium is growing, with support from civil society, corporations, the fishing sector and financial institutions. In June, the European Parliament strengthened its backing for a moratorium and called on the European Commission and EU member states to join it. Numerous bilateral conversations are already happening.

We must take this step to add the deep seabed to the short list of relatively untouched regions on Earth, alongside Antarctica, that are too important and too fragile to open up and exploit. And we must do so soon.

Helen Scales is a marine biologist and author of

The extremely rare bigfin squid, a deep-sea creature found more than 2 kilometres underwater, has been spotted in Australian waters for the first time.

Deborah Osterhage at CSIRO in Hobart, Australia,��and her colleagues came across the squid during underwater surveys in the Great Australian Bight, an open bay off Australia’s southern coast.

“I knew exactly what it was when I saw it, probably because I’m a bit of a deep sea geek,” says Osterhage. “They’re very rarely seen around the world.” Only three sightings had previously been recorded in the southern hemisphere.

Bigfin squid (Magnapinna) have a distinctive appearance: they have large fins that make their main bodies nearly as wide as they are long, and also have extremely long, filament-like tentacles, which they can bend into an elbow-like appearance. These tentacle filaments are retractable and have tiny suckers on them, which might be used for feeding.

The researchers first spotted the squid at a depth of more than 2100 metres, during a survey in which a camera��was towed underwater beneath a ship.

The squid were spotted multiple times during subsequent surveys. “We were able to see differences in their body ratios and their body lengths to confirm that they were actually five different individuals,” says Osterhage.

The researchers measured one of the squid using a pair of lasers, finding it was 1.8 metres long, with its tentacles accounting for 1.68 metres of that length.

The closest distance between two of the five sightings was 300 metres apart.��It was unusual to find multiple bigfin squid in such close proximity, says Osterhage. “Normally, you only get reports of one, maybe two.”

Because so little is known about the squid, more sightings would shed light on their distribution, says Osterhage.

The researchers noticed that some of the squid had coiling in their tentacle filaments, and also observed the creatures very close to the sea floor. One was in a horizontal position with its tentacles trailing behind it, which has never been seen before.