In August 2012, Douglas Bastos, a graduate student in Brazil’s Instituto Naciel de Pesicvas da Amazonia, was exploring a remote waterway in the Amazon rainforest when he came across a small lake with electric gels.
Electric eels, despite their names, are actually a type of knife, believed to be solitary creatures. And yet Dr. Bastos had eyes over 100 of them. Then things got more heated.
Dr. Bastos watched, amazed, as the mass of eels began to tightly encircle the groups of tetra fish into pack balls and bombard them with synchronized lightning strikes that flew them.
“When I saw Tetras jumping after the attacks, I was in shock,” Dr. Bastos said. “Group hunting is a rare occurrence in freshwater fishes. My first reaction was to steer the boat and get the camera. “
Two years later, Drs. Researchers at Bastos and the Smithsonian National Museum of Natural History returned to the area to study this unusual phenomenon. The findings of their study, published Thursday in the journal Ecology and Evolution, overturned the idea that electric eels are particularly solitary predators and raise new questions about the lives of these small-minded fish.
When the researchers returned to the site, along the Brazilian River Iiri, they confirmed that in 2012, Drs. The electric eels that Bastos inspected were Volta’s electric eels, a recently discovered species that can reach up to 8 feet in length and are capable of being produced. 860-volt electric shock – the strongest electric discharge of any animal.
For the last 250 years, scientists believed that all electric eels belong to the same species, but in 2019, Smithsonian researcher C.W. Research by David de Santana proved that there are at least three species, the largest and most electric electric eel of Volta.
The new study co-authored Drs. According to de Santana, such behavior was never documented in electric eels. “It was quite unexpected,” he said.
Typically, electric eels hunt alone, splatter on sleeping fish and collect them. But hunting in groups may enable predators to hunt prey that would otherwise be too fast, such as small tetras. Although many mammals, including wolves and orcas, are known to hunt in groups, the strategy is rarely employed by fish. Only nine species of fish, including goldsmith goats, are known to hunt in this way.
Dr. Bastos and Drs. De Santana analyzed more than 70 hours of footage of Volta’s electric eels, which the highly coordinated group hunts. At dawn and dusk, the disgusting, snakelike creature gathers in shallow water and starts swimming together in large circles. After swallowing thousands of small fish in dense balls, the eels split into cooperative hunting parties with two to 10 members.
After this, these teams will surround the schools of the terrified Tetra and send it to Tetra by leaping from the water. When the electrified fish came down, the eel quickly devoured them.
Although researchers were not able to measure the voltage of coordinated electrical strikes, they estimate that 10 volts of electric eels working together could create enough electric current for 100 light bulbs of electricity.
Researchers suspect these electric eels prevented their attacks by communicating via a low-voltage electric discharge.
Although it is unclear whether other species of lightning hunt in groups, experts say that is unlikely. “It is possible that all electric eel species hunt cooperatively,” said Cory Evans, a fish ecologist at Rice University.
Dr. De Santana and his colleagues plan to collect tissue samples from electric eels to return to the Iril River and equip them with radio tags to determine if family relationships play a role in cooperation with another fish, As it does with other packs. Hunter. He also has plans to collect some bricks from the wild, so that he and his colleagues learn more about how these animals communicate.
“There’s a lot to learn,” he said.