Bull Sharks Form Friendships and Choose Who They Swim With

Bull sharks form social bonds and choose their companions, challenging the idea that they are solitary predators. These connections may help them learn, find food, and avoid conflict.

New research shows that bull sharks develop social relationships with specific "friends." This goes against the common belief that these animals are mostly solitary.

The study took place at the Shark Reef Marine Reserve in Fiji. It found that bull sharks do not interact randomly. Instead, they show "active social preferences," choosing certain individuals to be with and avoiding others.

The research team included scientists from the University of Exeter, University of Lancaster, Fiji Shark Lab, and Beqa Adventure Divers.

"As humans, we have many social relationships, from casual friends to best friends. We also actively avoid certain people. These bull sharks do similar things," said Natasha D. Marosi. She is the lead author, an Exeter researcher, and founder of Fiji Shark Lab.

Bull Shark Social Behavior

These findings come from six years of observations. Researchers studied 184 bull sharks across three life stages: sub-adult, adult, and advanced-adult.

They looked at broad patterns of sharks staying close to each other. They also observed detailed behaviors like "lead-follow" movements and parallel swimming.

Adult sharks were the most social. Individuals tended to interact with others of similar size.

"Many people think sharks are solitary. But our study shows they have rich and complex social lives," said Professor Darren Croft. He is from Exeter’s Centre for Research in Animal Behaviour.

"We are just starting to understand the social lives of many shark species. Like other animals, they likely benefit from being social. This might include learning new skills, finding food and mates, and avoiding fights."

Social Advantages and Age

The study found that both male and female bull sharks often associate with females. However, males generally had more social connections overall.

"Male bull sharks are smaller than females. So, one benefit they might get from being more social is protection from aggressive fights with larger sharks," Marosi said.

Adult sharks formed the main "core" of the social network. Advanced adult and sub-adult sharks were generally less connected.

"This study used data from one of the longest-running shark ecotourism dive sites in the world," said Dr. David Jacoby from Lancaster University. "This gave us a unique chance to watch the detailed behavior of these sharks over many years as they grew and managed their social relationships."

Marosi added that the Shark Reef Marine Reserve is a protected area. Many sharks gather there year-round. This allowed researchers to study individual sharks repeatedly over time.

"Our results show that older sharks tend to be less social," Marosi noted. "These older sharks have many years of experience hunting and mating. Sociality may not be as important for their survival as it is for younger sharks."

Sub-adult bull sharks rarely visit the Reserve. They usually live in near-shore habitats. Juvenile bull sharks are found in Fiji’s rivers and estuaries.

"During these early life stages, they need to avoid predators, including adult bull sharks," Marosi explained. "We do have some bolder sub-adults at the Reserve. They have formed social ties with some adult sharks. These older sharks may help them join the social network and learn new things."

Why Shark Social Behavior Matters

Marosi stressed that understanding shark social behavior better could help create conservation policies. It could also improve management strategies. Fiji Shark Lab is already working with Fiji’s Ministry of Fisheries to use these findings in ongoing protection efforts.

Deep Dive & References

Rolling in the deep: drivers of social preferences and social interactions within a bull shark aggregation in Fiji - Animal Behaviour, 2026

The research was funded by the Fiji Shark Lab, Hai Stiftung Shark Foundation, and the Waitt Foundation.