[ad_1]
In August 2012, Douglas Bastos, then a graduate student of the Instituto Nacional de Pesquisas da Amazônia in Brazil, was exploring an isolated waterway in the Amazon rainforest when he came across a small lake teeming with electric eels.
Electric eels, which despite their name are actually a type of knife, were considered solitary creatures. And yet, in front of Dr. Bastos’ eyes, there were more than 100. Then things got even more bumpy.
Dr Bastos watched in astonishment as the mass of writhing eels begin to gather groups of tetras into tight balls and bombard them with synchronized electric attacks that made them fly.
“When I saw the grouse jump after the attacks, I was in shock,” said Dr Bastos. “Group hunting is a rare occurrence among freshwater fish. My first reaction was to run over to the boat and grab a camera.
Two years later, Dr Bastos and researchers from the Smithsonian National Museum of Natural History returned to the area to study this unusual phenomenon. The results of their study, published Thursday in the journal Ecology and Evolution, overturn the idea that electric eels are exclusively solitary predators and raise new questions about the lives of these little-known fish.
When the researchers returned to the site, along the banks of the Iriri River in Brazil, they confirmed that the electric eels Dr Bastos observed in 2012 were Volta electric eels, a recently discovered species that can reach 8 feet. long and capable of producing electric shocks of 860 volts – the strongest electric shock of all animals.
For the past 250 years, scientists thought that all electric eels were of the same species, but in 2019, research by C. David de Santana, a Smithsonian researcher, proved that there are at least three species, the largest and most electrified being the Volta Electric Eel.
According to Dr. de Santana, co-author of the new study, no such behavior has ever been documented in electric eels. “It was quite unexpected,” he says.
Typically, electric eels hunt on their own, sneaking up on sleeping fish and shocking them to subdue them. But group hunting can allow predators to hunt prey that would otherwise be too fast, such as tiny tetras. Although many mammals, including wolves and orcas, are known to hunt in groups, the strategy is rarely used by fish. Only nine species of fish, including the golden saddle goatfish, are known to hunt this way.
Dr Bastos and Dr de Santana analyzed more than 70 hours of footage of electric Volta eels leading highly coordinated group hunts. At dawn and dusk, the slimy snake-like creatures would congregate in shallow water and begin swimming together in large circles. After collecting thousands of small fish into dense balls, the eels split into cooperative hunting groups of two to 10 members.
These groups would then surround the terrified tetra schools and launch joint electric attacks, causing the tetra to leap out of the water. When the electrocuted fish splashed, the eels quickly devoured them.
Although the researchers were unable to measure the voltage of the coordinated electric attacks, they estimate that 10 Volta electric eels working together could create an electric current strong enough to power 100 light bulbs.
Researchers suspect these electric eels of orchestrating their attacks by communicating through low-voltage electric shocks.
While it’s not clear whether other species of electric eels hunt in groups, experts say it’s not unlikely. “It’s possible that all species of electric eels hunt cooperatively,” said Kory Evans, fish ecologist at Rice University.
Dr de Santana and his colleagues plan to return to the Iriri River to collect tissue samples from the electric eels and equip them with radio tags so they can determine if the family relationship plays a role in the fish’s cooperation, as it does this with other packages. hunters. He also plans to collect certain eels from the wild so that he and his collaborators can learn more about how these animals communicate.
“There is so much to learn,” he says.
[ad_2]
Source link