[ad_1]
Electric eels don’t seem to be the loners we thought they were.
In a small lake at the bottom of the Amazon River basin in Brazil, scientists for the first time recorded the fish not only living together, but actively working together to feed and slaughter their prey.
There is even evidence that the strategy works. Abundant electric eels from the Volta (Electrophorus voltai, not a real eel but a type of knife) found alive in the lake, many were over 1.2 meters (4 feet) long and thriving.
“This is an extraordinary find,” said ichthyologist Carlos David de Santana of the Smithsonian Institution’s National Museum of Natural History. “Nothing like this has ever been documented in electric eels.”
Not much is known about the Volta Electric Eel. The fish was only recently discovered in a lake along the Iriri River, and officially described and recognized as a separate species last year. But it’s powerful, capable of discharging a single shock of over 860 volts – more powerful than any other registered electric eel.
De Santana and his team first observed electric eels hunting in groups in 2012. More than 100 individuals appeared to work together to round up and kill their prey so the whole school could feed. But one observation was not enough to classify hunting as normal behavior.
In 2014, the team returned and found even more Volta Electric Eels, so they got to work observing and recording the animals. In 72 hours of continuous observation, they saw the electric eels engage in five more hunts. Not only was this enough to classify the behavior as normal, but it allowed researchers to observe and record exactly how these “social predatory events” occur.
Day and night, the electric eels were mostly resting. At dusk and dawn, at dusk, the electric eels stirred to hunt. This, the team noted in their article, is unusual: Typically, Volta’s electric eels are only seen feeding at night and solo.
The difference here is striking. On each occasion, over 100 individual electric eels gathered and began to swim in circles, effectively gathering groups of small fish, mostly characins, into a “ball of prey” which they gradually ejected into lesser waters. deep.
Then, once the prey ball was tightly contained with nowhere to go, up to 10 of the electric eels advanced and launched a powerful joint strike, stunning the prey – which leapt out of the water before falling back down. , foolish.
“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 were to discharge at the same time, they could produce up to 8,600 volts of electricity. “said de Santana. . “That’s about the same voltage needed to power 100 light bulbs.”
Once the prey was stunned, the school could enter and feed at leisure.
Each hunt, according to the team, lasted about an hour and involved five to seven electric hits.
“Group hunting is pretty common in mammals, but it’s actually quite rare in fish,” de Santana said. “There are only nine other species of fish known to do this, which makes this find really special.”
Nonetheless, while the hunts might be normal, the team still thinks they might be quite rare. In their interviews with locals, the congregation of electric eels and hunting behavior were not mentioned. So whether electric eels congregate to hunt or go solo may depend on the right conditions, such as high prey abundance and specific locations with plenty of shelter for large numbers of these fish.
While much is still unknown, the team believe the electric eels will likely return to the lake every year. They launched a citizen science project called Projeto Poraquê, where residents can record their observations; this data could prove invaluable. And the team plans to return to the scene in hopes of seeing the animals again.
“In addition to trying to locate additional populations of eels involved in group foraging, our future field and laboratory studies will study social predation in electric eels with a focus on the link between the population, social structures, genomics and electrogenesis, ”they wrote. in their article.
“In short, this case offers a unique perspective for future studies on the evolutionary interaction between predation and escape tactics in vertebrates.”
The research was published in Ecology and evolution.
[ad_2]
Source link