NewsOpener (EUA)

Shocking discovery: Electric eels hunt in packs in Amazon rivers

Publicado em 14 janeiro 2021

When darkness comes, electric eels emerge from South American river bottoms to attack their prey with up to 860 volts of electricity—enough to kill a person. Now, scientists have revealed the snakelike fish don’t always go it alone: They hunt in packs, similar to wolves, orcas, and some species of tuna. The finding, a first among electric fishes, may open the way for new studies to investigate when social predation evolved among fishes.

“I was shocked,” says Douglas Bastos, a biologist at the National Institute of Amazonian Research who first saw a group attack in 2012. Usually the eels, which can grow as long as a broomstick and weigh up to 20 kilograms, prey alone at night, targeting single resting fishes, he notes. “This behavior is unprecedented for electrical eels and also rare among freshwater fishes.”

Bastos witnessed the attack on an expedition looking for endangered fish in northern Brazil. Two years later, he went back for a closer look. Camping alone in the middle of the Amazon—a 5-day journey by boat from the nearest city of Altamira—he filmed hundreds of electric eels in groups of 10 repeatedly attacking small tetra fishes on the Iriri River, a tributary of the Xingu River (which is a tributary of the Amazon River) in northern Brazil. The eels were Electrophorus voltai, which deliver the strongest shock ever measured in a living animal.

Most of the time, the eels rested at the bottom of the river. But at dawn and dusk, they moved to a shallow pool at the riverbank of the Iriri where they herded shoals of fish and launched joint shock attacks, immobilizing and devouring their prey (see video, above). Each hunt usually took 2 hours and involved up to seven attacks the researchers report today in Ecology and Evolution.

So far, the group attacks have only been recorded in the low-water season, which runs from June to November. During those months, which see a significant reduction in rainfall, fishes in the region’s rivers are squeezed into far less water than normal, making them easy pickings for the eel packs. The eels simply have to find a pool full of fish and ambush them. In the high-water season, prey would likely have a much better chance of keeping a safe distance—and getting away, says co-author Carlos David de Santana, a co-author and biologist at the Smithsonian Institution’s National Museum of Natural History.

The researchers don’t know how this behavior evolved, how widespread it is, and whether it happens only during the low-water season. But Santana has some thoughts on how the eels might pick out their groups. “This social predation could have emerged based on a simple individual-level rule: Keep foraging with the same individuals when successful, and then a stable group forms.”

The study is “a fascinating example of careful natural history detective work,” says William Crampton, a biologist at the University of Central Florida who was not part of the work. He has been studying electric fishes for 25 years and says the findings could spur further research into how the eels use electric discharges to navigate and communicate.

Bastos and his colleagues next plan to sequence the genomes of the eels, in hopes of identifying genes linked to social predation shared by other animals that display this behavior, including mammals like whales. This could give them clues to better understand the history of this trait’s evolution among a wide variety of animals.

Crampton suspects other species of electric eels may utilize the same hunting strategy. On a recent trip to Guyana, he says he heard reports from Indigenous peoples about shoals of fish jumping up out of the water near large groups of electric eels of another species (E. electricus). “I’ve never witnessed this behavior myself, but if these stories are true, it suggests that the behavior might not be restricted to E. voltai.”

In any event, the researchers will have to act fast, because human destruction of the Amazon is wiping out these habitats, Santana says. “It is possible that in 5 or 10 years, these locations will not be preserved anymore.” 

Essa notícia também repercutiu nos veículos:
Galileu online 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) 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 (CE) 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 online 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) ScienceAlert (Austrália) 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) 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 104.9 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