Like us, they cultivate different relationships and avoid certain individuals
Por seis anos, pesquisadores em Fiji observaram tubarões-touro escolherem companheiros, evitarem certos indivíduos e manterem laços duradouros — comportamentos que a biologia marinha raramente ousou atribuir a essas criaturas. O estudo, conduzido com 184 animais no Shark Reef Marine Reserve, revela que a vida social dos tubarões é mais rica e estruturada do que um século de ciência supôs. No momento em que a humanidade aprende a conviver com o oceano, descobrir que seus habitantes mais temidos também cultivam relações é um convite à revisão profunda de nossos preconceitos.
- Durante seis anos, os mesmos pares de tubarões-touro reapareceram juntos repetidamente, sugerindo preferências individuais genuínas — não coincidências aleatórias do mar.
- A descoberta tensiona décadas de literatura científica que tratou o tubarão como predador solitário e indiferente, obrigando pesquisadores a rever premissas fundamentais.
- Redes sociais internas revelam estratégia: machos menores cultivam mais conexões para navegar hierarquias sem confronto direto com animais maiores.
- Especialistas alertam que protocolos de conservação e segurança baseados na imagem do predador sem vida interior podem estar respondendo a um problema que não existe.
- O campo começa a se reorganizar: se tubarões têm opiniões sobre com quem conviver, a ciência precisa aprender a fazer as perguntas certas antes de concluir que não há nada a ver.
Por seis anos, pesquisadores do Fiji Shark Lab acompanharam 184 tubarões-touro no Shark Reef Marine Reserve e documentaram algo que os livros de biologia marinha não previam: esses animais escolhem seus companheiros. Os mesmos pares reapareciam juntos ao longo dos anos, mantendo proximidade física e movimentos coordenados — um liderando, o outro seguindo. Não era acaso. Era preferência.
Natasha Marosi, fundadora do laboratório e líder da pesquisa, descreveu o comportamento em termos que soam familiares a qualquer observador de grupos humanos. Os tubarões, segundo ela, cultivam diferentes tipos de relações e desviam de certos indivíduos — exatamente como fazemos. Os dados confirmavam uma seletividade real, o tipo de comportamento que só aparece quando uma criatura tem opiniões sobre quem quer por perto.
As redes sociais formadas não eram uniformes. Adultos em fase reprodutiva ocupavam posições centrais e mantinham laços estáveis. Machos menores, em desvantagem de tamanho frente às fêmeas, compensavam cultivando mais conexões — uma forma de seguro social para navegar hierarquias sem conflito direto.
Darren Croft, pesquisador de comportamento animal na Universidade de Exeter, situou os achados num contexto mais amplo: décadas de pesquisa haviam perdido algo fundamental porque a premissa inicial estava errada. Tubarões não deveriam ser sociais — então ninguém olhou com atenção suficiente para perceber que eram.
O que emerge de Fiji é mais do que uma correção científica. Se tubarões-touro — animais de até 3,5 metros, presentes entre as espécies mais associadas a ataques humanos — possuem laços reais e navegam hierarquias sociais, então as estratégias de conservação e convivência precisam ser repensadas. A imagem do predador imprevisível e sem vida interior começa a ceder lugar a algo mais complexo, e mais verdadeiro.
For six years, researchers stationed themselves at Shark Reef Marine Reserve in Fiji to watch 184 bull sharks move through the water. What they found upended a century of marine biology textbooks: these animals were not drifting through the ocean as solitary hunters, indifferent to one another. They were choosing their companions.
The study documented two distinct patterns of interaction. Bull sharks maintained physical proximity—staying within roughly one body length of each other—and they engaged in coordinated movement, with one animal leading while another followed. But the crucial finding was this: these pairings were not random. The same sharks appeared together repeatedly, across years. They seemed to prefer certain individuals and actively avoid others. It was, in essence, friendship.
Natasha Marosi, who founded the Fiji Shark Lab and led the research, described the behavior in terms that would sound familiar to anyone who has watched human social groups form. "Like us, they appear to cultivate different kinds of relationships and steer clear of certain individuals," she told the Times. The comparison was not metaphorical flourish. The data showed genuine selectivity—the kind of thing you see when a creature has opinions about who it wants to spend time with.
Bull sharks are formidable animals. They reach lengths of up to 3.5 meters and can weigh as much as 230 kilograms. They are found in warm waters worldwide and possess an unusual tolerance for freshwater, turning up in rivers and estuaries where most sharks cannot survive. They occupy a particular place in human consciousness: they are among the three shark species most frequently implicated in attacks on people, alongside the great white and the tiger shark. Yet such incidents remain statistically rare. The stereotype of the bull shark—aggressive, unpredictable, a mindless eating machine—has persisted despite the rarity of actual harm.
The social networks these sharks formed were not uniform. Age and size mattered. Adult sharks in their reproductive years occupied central positions in the network, maintaining stable bonds. Smaller males, generally outweighed by females, formed more connections than their larger counterparts. This pattern suggested a strategy: by cultivating more relationships, younger or smaller males could navigate a hierarchy without constant conflict. It was a form of social insurance.
Darren Croft, an animal behavior researcher at the University of Exeter, placed the findings in broader context. "Contrary to common perception, sharks have relatively rich and complex social lives," he said. "We are only beginning to understand how these interactions work." The implication was clear: decades of research had missed something fundamental about these animals because the starting assumption was wrong. Sharks were not supposed to be social. So researchers had not looked closely enough to see that they were.
The work matters beyond academic curiosity. If sharks possess genuine social bonds—if they have preferences, if they navigate hierarchies, if they form alliances—then our understanding of how to coexist with them shifts. Conservation strategies built on the assumption of solitary, territorial animals may miss the mark. Safety protocols designed around the image of a mindless predator may be addressing the wrong problem. What emerges from Fiji is an invitation to see the bull shark not as a caricature, but as a creature with an inner life as real and complex as any other.
Citações Notáveis
Like us, they appear to cultivate different kinds of relationships and steer clear of certain individuals— Natasha Marosi, Fiji Shark Lab founder
Contrary to common perception, sharks have relatively rich and complex social lives. We are only beginning to understand how these interactions work.— Darren Croft, University of Exeter animal behavior researcher
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter that sharks form friendships? Aren't they still dangerous?
Danger and sociality aren't opposites. A social animal has preferences, hierarchies, ways of resolving conflict. That's actually more predictable than a solitary one. If we understand how they relate to each other, we might understand how they relate to us.
The study tracked the same sharks for six years. How did they identify individual animals?
Tagging and observation. In a reserve, you can follow the same individuals over time. The researchers weren't guessing—they were documenting repeated encounters between the same pairs.
You mentioned smaller males form more connections. Is that because they're weaker?
Partly. But it's also strategy. If you're smaller, you can't dominate through size, so you build alliances instead. It's a form of social climbing.
Does this change how we should think about shark attacks?
It suggests attacks might be less random than we assume. If sharks have social structures, preferences, ways of reading situations, then maybe we've been misunderstanding the encounters all along.
What's the next question the researchers should ask?
How do these bonds form? What triggers preference? Do they communicate in ways we haven't detected? There's a whole world of shark behavior we're only now beginning to see.