Outsider (EUA)

Electric Eels Documented Hunting and Shocking Prey in Packs For the First Time

Publicado em 18 janeiro 2021

Long pegged as a species of illusive loners, electric eels have now been documented working in packs to forage and hunt their prey.

“This is an extraordinary discovery,” says ichthyologist Carlos David de Santana of the Smithsonian Institution’s National Museum of Natural History. “Nothing like this has ever been [seen] in electric eels.”

Nothing like it, indeed. Scientists have, for the first time, recorded proof of electric eels working in “packs” to hunt their prey. A days-old publishing in Ecology & Evolution details how a group of Volta’s electric eels (Electrophorus voltai) is not only living together but coordinating in numbers to forage. The behavior extends to active “pack” hunting, as well.

Their current population density seems to imply his previously unheard of strategy is working, too. Together, the eels are thriving in the small lake they call home at the Amazon River basin in Brazil.

it is worth noting, however, that these plentiful Volta’s electric eels are not true eels – but a type of knifefish, ScienceAlert clarifies. Regardless, scientists have long thought the electricity-wielding Volta’s to be similarly reclusive as are true eels. The species only recently became a distinct classification in 2020.

“Over 100 individual electric eels aggregated and started swimming in circles…”

As such, scientists are still learning of the Volta’s electric eel. First discovered in a still water lake along the Iriri River, the fish can grow to be a staggering 4 feet (1.2 meters) long. Their heft means they pack a harsh electrical discharge, too: one more powerful than any true eel on record. At 860+ volts, Volta’s can deliver a debilitating shock to creatures several times their size.

The Smithsonian’s de Santana and his team first observed the electric eels’ pack mentality nearly a decade ago in 2012. In the years since, the scientists have painstakingly documented the species in effort to prove the behavior wasn’t a fluke, but rather a true strategy.

Now, thanks to eight years of observation and examination, de Santana can scientifically declare that these electric eels are, in fact, hunting in packs. And they’re good at it, too.

“During the day and night, the electric eels mostly rested,” ScienceAlert details. “At dusk and dawn, the twilight hours, the electric eels stirred themselves to hunt. This, the team notes in their paper, is unusual: Typically, Volta’s electric eels are only foraging at night and solo.”

Then came the revelation. “On each [hunting] occasion, over 100 individual electric eels aggregated and started swimming in circles, effectively herding groups of smaller fish, mostly characins, into a “prey ball” that they gradually chivvied into shallower waters,” ScienceAlert continues.

“Then, once the prey ball was tightly corralled with nowhere to go, up to 10 of the electric eels moved forward and launched a powerful joint strike, stunning the prey… Which would jump out of the water before falling back down, senseless. Once the prey was stunned, the shoal could move in and feed at leisure,” they conclude. Unreal.

Powerful hunters, indeed.

“If you think about it, an individual of this species can produce a discharge of up to 860 volts. So in theory if 10 of them discharged at the same time, they could be producing up to 8,600 volts of electricity,” de Santana speculates of the species. While electric eels don’t function to the same measurements or precision of our true voltage system, de Santana’s speculation still illustrates the potential power of these pack hunters very clearly.

“Hunting in groups is pretty common among mammals, but it’s actually quite rare in fishes,” de Santana continues. “There are only nine other species of fishes [that hunt in packs], which makes this finding really special.”

Locals, however, have yet to mention any observations that match de Santana’s findings. As such, his team thinks this behavior could still be either rare, a product of isolation, or both. To solve this last piece of the puzzle, scientists have launched a citizen science project known as “Projecto Poraque.” With it, locals can log their own findings on the electric eels.

“In addition to trying to locate additional populations of eels involved on group foraging, our future field- and laboratory-based studies will investigate social predation in electric eels focusing on the link between population, social structures, genomics, and electrogenesis,” the team writes in their paper, which is published in Ecology & Evolution.

What a time to be alive.

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[Source: ScienceAlert]

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