Bull Sharks Are Large, Aggressive Predators—but They Also Know How to Make ‘Friends,’ New Research Suggests

The animals probably socialize to learn new skills and to find food and mates

Sarah Kuta | Daily Correspondent

March 18, 2026

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With rows of razor-sharp teeth and powerful jaws, bull sharks are some of the most aggressive and dangerous sharks on the planet. Despite their fearsome reputation, these hulking creatures also seem to have a more sensitive side: Bull sharks form friendships of sorts with other members of their species, according to a study published March 17 in the journal Animal Behaviour.

“As humans, we cultivate a range of social relationships—from casual acquaintances to our best friends, but we also actively avoid certain people—and these bull sharks are doing similar things,” says lead author Natasha Marosi, a shark behavior researcher at the University of Exeter in England and the founder of the Fiji Shark Lab, in a statement.

Marosi and her colleagues spent six years observing 184 bull sharks—33 males and 151 females—at the Shark Reef Marine Reserve, a protected area off the southern coast of Viti Levu, an island of Fiji. Numerous shark species congregate at the reserve year-round because dive operators have been feeding them tuna for more than two decades. Feeding sharks, known as “provisioning,” is controversial. But, in this case, it gave scientists a rare opportunity to study the social lives of the enigmatic creatures.

The creatures in the study, which were either tagged or identified via unique features, like scars, were divided into three age categories: subadults that were not yet sexually mature, adults, and advanced adults past reproductive age. Researchers swam among the sharks five times a week between 2018 and 2023, making detailed notes about how the individuals interacted with one another and recording videos of the animals. Over the course of 473 dives totaling 8,192 minutes, they jotted down moments when sharks were within one body length of one another, as well as times when they swam alongside or behind each other.

The data revealed that sharks seemed to intentionally choose who they spent time with, preferring to associate closely with some individuals while actively avoiding others. The most common interactions were among sharks of a similar size.

Females were the most popular companions among both sexes, though males had more social connections, on average, the team found. Adults were the most social of all the age groups and seemed to form the core of the reserve’s bull shark social network.

The researchers think male sharks might have more to gain from being socially connected. Because males are physically smaller, hanging out with the larger, more dominant females “can ensure their place within the group and give them access to food resources at the site,” Marosi tells IFLScience’s Eleanor Higgs.

Younger sharks likely avoid socializing because they are vulnerable to attacks by adults, the researchers posit. The few bold individuals that did socialize with adults at the reserve might have been learning important life lessons from their more experienced peers.  

Older sharks, meanwhile, are probably less social because relationships are less crucial to their survival. They’re seasoned veterans that have “many years of experience hunting, navigating their environment, locating resources and choosing mates,” Marosi tells IFLScience.

Overall, sharks are often thought of as solitary creatures—sinister loners prowling around the world’s oceans in search of their next victims. But the findings add to the growing body of research that suggests these creatures deserve a more nuanced reputation.

They are “quite varied,” Marosi writes in an email to the Washington Post’s Brady Dennis. “We have highly social shark species on one end of the spectrum and solitary sharks on the other.”

In addition to bull sharks, past research has suggested that sand tiger sharks, reef sharks and lemon sharks may also have complex social lives. Understanding these social interactions could help conservationists better protect sharks, which are threatened by climate change, overfishing, bycatch, pollution and other challenges.

“Sharks are running the gauntlet,” Ryan Daly, an ecologist at the Oceanographic Research Institute based in South Africa, told National Geographic’s Brianna Randall last year. “In every country, they’re facing different types of threats on top of climate change.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.