It’s not just the Avengers who work best as a team: turns out electric eels also assemble to defeat their foes. Or at least catch their next meal.

Although previously thought to be solitary predators, new research reveals the slippery freshwater fish can co-ordinate to zap their prey.

While monitoring wildlife in the Amazon river, scientists from Smithsonian's National Museum of Natural History discovered groups of up to 10 eels may form a pack to attack small fish known as tetras. After herding them into a tightly-packed ball in shallow waters, the eels then deliver a synchronised high-voltage strike.

"This is an extraordinary discovery," Dr David de Santana, lead author of the new study, said.

"Nothing like this has ever been documented in electric eels. Hunting in groups is pretty common among mammals, but it's actually quite rare in fishes.

“There are only nine other species of fish known to do this, which makes this finding really special.”

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Electric eels – which are actually a type of knifefish, not actual eels – are capable of discharging up to 860 volts of electric. They produce this charge through a specialised organ made up from cells known as electrolytes, which take up around 80 per cent of their metre-long bodies. These cells (each carrying less than 100 millivolts), link together to form a biological battery.

"In theory, if 10 eels discharged at the same time, they could be producing up to 8,600 volts of electricity," said de Santana. "That's around the same voltage needed to power 100 light bulbs."

But what would happen if an eel shocked a human? As de Santana knows first-hand, although the initial shock lasts for a mere two-thousandths of a second, it can still prompt a muscle spasm capable of knocking you off your feet.

Although it was believed that there was only one species of electric eel for 250 years, Dr de Santana and his colleagues have also unearthed an extra two varieties – alongside 85 new species of other electrical fish.

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But while only recently discovered, de Santana fears these eels may soon come under threat due to deforestation and climate change.

"Electric eels aren't in immediate danger, but their habitats and ecosystems are under immense pressure,” he explained.

"This paper is an example of how much we still don't know, how many organisms whose life histories we don't yet understand."

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Thomas Ling
Thomas LingDigital editor, BBC Science Focus

Thomas is Digital editor at BBC Science Focus. Writing about everything from cosmology to anthropology, he specialises in the latest psychology, health and neuroscience discoveries. Thomas has a Masters degree (distinction) in Magazine Journalism from the University of Sheffield and has written for Men’s Health, Vice and Radio Times. He has been shortlisted as the New Digital Talent of the Year at the national magazine Professional Publishers Association (PPA) awards. Also working in academia, Thomas has lectured on the topic of journalism to undergraduate and postgraduate students at The University of Sheffield.