(CNN)Electric eels have been found to hunt in packs in the first documented case of its kind, which researchers have called an "extraordinary discovery."
Scientists working in the Brazilian Amazon River basin were surprised to find a small lake containing more than 100 adult electric eels, which are usually found to be solitary animals, and stunned to see them cooperating to hunt fish, according to a press release from the Smithsonian Natural History Museum on Thursday.
"This is an extraordinary discovery," said the museum's fish research associate David de Santana, who led the research team, in the press release. "Nothing like this has ever been documented in electric eels."
The electric eels -- a type of knifefish -- were living in a lake on the Iriri river in Pará state, northern Brazil.
They would work together to push small tetra fish into tight shoals, before hunting parties of up to 10 eels would split from the main group and attack the fish, stunning them.
This behavior is reminiscent of packs of wolves and pods of killer whales, according to the press release, and is novel in electric eels.