ScienceAlert (Austrália)

For The First Time, Electric Eels Have Been Seen Hunting And Zapping Prey as a Group

Publicado em 15 janeiro 2021

Electric eels appear to not be the loners we thought they were.

In a small lake deep in the Amazon River basin in Brazil, scientists have for the first time recorded the fish not just living together, but actively working together to forage, and to bring down their prey.

There's even evidence that the strategy is working. Of the plentiful Volta's electric eels (Electrophorus voltai, not a true eel but a type of knifefish) found living in the lake, many were over 1.2 metres (4 feet) in length and thriving.

"This is an extraordinary discovery," 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 Volta's electric eel. The fish was only recently discovered in a lake along the Iriri river, and officially described and recognised as a distinct species last year. But it packs a punch, able to discharge a single shock in excess of 860 volts – more powerful than any other electric eel on record.

De Santana and his team first observed the electric eels hunting in a group in 2012. Over 100 individuals seemed to work together to herd and kill prey so that the entire shoal could feed. But one observation wasn't enough to classify the hunt as normal behaviour.

In 2014, the team returned and found even more Volta's electric eels, so they got to work observing and recording the animals. Over 72 hours of continuous observation, they saw the electric eels engage in five more hunts. Not only was this enough to classify the behaviour as normal, it allowed the researchers to observe and record exactly how these "social predation events" occur.

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

The difference here is striking. On each 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.

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.

"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 speculated. Of course, electric eels don't function as precisely as electrical wiring in our homes.

Once the prey was stunned, the shoal could move in and feed at leisure.

Each hunt, the team found, took around an hour and involved five to seven electrical strikes.

"Hunting in groups is pretty common among mammals, but it's actually quite rare in fishes," de Santana said. "There are only nine other species of fishes known to do this, which makes this finding really special."

Nevertheless, while the hunts may be normal, the team still believes they could be pretty rare. In their interviews with locals, the electric eels' congregation and hunting behaviour wasn't mentioned. So, whether the electric eels gather to hunt or go solo could be dependent on the right conditions, such as high prey abundance, and specific locations with lots of shelter for large numbers of these fish.

While a lot is still unknown, the team believes the electric eels likely return to the lake on an annual basis. They have launched a citizen science project called Projeto Poraquê, where locals can log observations; those data could prove invaluable. And the team is planning to return to the location in the hope of observing the animals again.

"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," they wrote in their paper.

"In short, this case offers a unique perspective for future studies on the evolutionary interplay between predatory and escape tactics among vertebrates."

The research has been published in Ecology & Evolution.

Essa notícia também repercutiu nos veículos:
Yahoo! BOL Agência Brasil IstoÉ online IstoÉ Dinheiro online Yahoo! Yahoo! G1 O Povo Nature (Reino Unido) online INPA Scienmag Science Magazine (Reino Unido) Phys.Org (Reino Unido) Smithsonian Insider (EUA) Galileu online Cultura Amazônica Amazônia Sem Fronteira Rádio Web Coopnews The New York Times (EUA) online Brasil Amazônia Agora ScienceDaily (EUA) News Break (EUA) Flipboard (EUA) CRWeWorld Brazil (EUA) Fresh Hourly - the latest news The Daily Ripple (EUA) TechCodex (Índia) Climatechange (Irlanda) i-NEWS - India Right Now Group Amazônia Sem Fronteira Online Multimidia Saense Planeta online BBC Mundo (Reino Unido) AlcidesFaria Portal Debate Carajás Saber Atualizado Em Tempo (Manaus, AM) online Ecoamazônia Plantão News (MT) Plurale online Mundo e Meio Portal do Holanda Polit (Rússia) Ars Technica (EUA) Replicário Diário do Amazonas Mato Grosso Digital Revista Amazônia Blog Jornal da Mulher Correio Paraense Revista Ecológico online Sou Ecológico Dom Total Jornal do Vale (Ceres, GO) online Mato Grosso Mais Notícias Primeira Edição Estação da Notícia Gazeta Minas a informação direta Informe Baiano D24AM DF Manchetes Dia a Dia On-line Bocaina Informa Diário MS News Atual MT Cenário MT CGN Amazônia Sem Fronteira O Bom da Notícia Midia News Campo Grande O Povo online O Rolo Notícias Jornal Fogo Cruzado DF JorNews Jornal Dia Dia Enfoque MS Jornal de Jundiaí online Portal R3 Portal Ribeirão Preto Portal Roma News Portal Mariliense Nosso Goiás Portal Notícias Bahia Tangará em Foco Sistema Costa Norte de Comunicação Sou de Sergipe Dinheiro Rural online TNH1 Tudo em Dia Portal Uno Midias Xeretando Portal Flagrante Portal Mato Grosso Jornal O Diário (MT) online - Clique F5 Portal Brasil Empresarial Portal Paraná Empresarial Portal Norte de Notícias Portal Marcela Rosa Blog da Amazônia Amazônia Revista Ecológico online Jornal Noroeste News Sou Ecológico Rádio Cultura FM 101,7 Rádio Nova Aliança FM 105,9 Rádio Cidade Nova FM 104,9 Rádio Liberdade FM 87,9 Rádio SAT Peruíbe SP Diário da Amazônia online Empresas S/A Falando de Gestão FarolCom Jornalismo 24 Horas Amazônia Brasil Rádio Web Brasil Amazônia Agora Coisas da Vida Diário do Amapá Revista Construtores Portal de Finanças Portal Fator Brasil Portal Paraná Empresarial Marcas e Mercados Radar Amazônico 3 Poderes MT Sociedade Científica eCycle Portal Amazônia ContilNet Notícias O Povo Amazonense Portal AM Revista Faces 18 Horas Piscishow e Avisuleite Portal Plural Pesca & Companhia online TN Online Portal Marcela Rosa Jornal de Piracicaba online ZAP Notícias - AEIOU (Portugal) Diário do Pará online Balanço Paraense Circuito D Seu Bairro Hoje Clube News Goiás Notícias Rômulo de Oliveira Martins: Advocacia e Assessoria Jurídica Primeira Edição online New Atlas (Austrália) Green Savers (Portugal) Kepusz (China) Parallaxi Magazine (Grécia) ScienceNet (China) BBC News Persian CAS - Chinese Academy of Sciences (China) SciToday (China) Ok diario (Espanha) Lega Nerd (Itália) Futuro360 (Chile) Everyeye Tech (Itália) Sciencepost (França) El Imparcial (México) Uncommon Descent Outsider (EUA) Gizmodo (EUA) Yahoo! (EUA) Guest Articles Sveriges Radio (Suécia) Tribuna Press Em Rondônia BBC News Indonesia (Indonésia) (Indonésia) detikNews (Indonésia) People News Chronicle Spektrum (Alemanha) online Greenreport (Itália) La Vanguardia (Espanha) online Kodami (Itália) Sciences et Avenir (França) online Telex (Hungria) GuruMeditation Universo Racionalista Head Topics (Indonésia) SINDOnews (Indonésia) Super Interessante online Notizie Scientifiche (Itália) Science (EUA) online In de Spiegel (Holanda) Animals Today (Holanda) X-MOL (China) This Week News (EUA) We Found This Science News Science News for Students (EUA) Geeky News (República Tcheca) (EUA) MLActu (França) N+1 - (Rússia) (China) BleNews (Espanha) Vikerraadio (Estônia) (China) NewsOpener (EUA) Portal 24h TechCodex (Índia) Jornal Agora Amazonas (Indonésia) ScienceNet (China) Perfil (Brasil) Portal o Vento Gizmodo en Español (EUA) Caderno Político Prime Times (Índia) MimicNews Modais em Foco Portal GRNews Focado News Inforbrnet Giro de Notícia Rádio Guaribas FM Portal Alta Notícias SouSorocaba Notícias Indaiatuba Expressão Mearim OffNews Portal Plural Corban Aquarismo Paulista Brasil em Folhas online Clazoom Folha de Aparecida Jornal Rede 1 - JR1 Portal Notícia e Pesquisa Dia a Dia Notícia Portal Edilene Mafra