Forget everything you thought you knew about sharks being cold-blooded loners. It turns out bull sharks have best friends, casual acquaintances, and individuals they'd rather avoid — a social setup that sounds remarkably like a school playground. Or, for that matter, an office.
A new study published in the journal Animal Behaviour has found that bull sharks actively choose who they spend time with, forming stable social bonds with preferred companions while steering clear of others. The research, based on six years of observations at the Shark Reef Marine Reserve in Fiji, tracked 184 individual bull sharks — some of whom even have names.
Meet Chunky, an adult bull shark, who was photographed swimming in parallel with Lady Lazarus, a younger sub-adult female. It's exactly the kind of companionship the researchers documented again and again.
"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," said lead author Natasha D. Marosi, a University of Exeter researcher and founder of the Fiji Shark Lab.
A Social Network Under the Waves
The research team — from the University of Exeter, Lancaster University, Fiji Shark Lab, and Beqa Adventure Divers — examined both broad patterns of association and fine-scale behaviours such as "lead-follow" movements and parallel swimming. Two sharks were considered associates if they stayed within one body length of each other.
Adult sharks turned out to be the social butterflies of the group, forming the central core of the network. They tended to gravitate toward partners of a similar size, and both sexes showed a preference for hanging out with females.
Males, despite being physically smaller than females, had more social connections overall — perhaps because being well-connected helps them avoid aggressive run-ins with larger sharks.
Growing Old and Grumpy
In a finding that will resonate with anyone who's become more selective about their social calendar with age, older bull sharks were notably less social.
"These older individuals have many years of experience honing their skill sets, hunting and mating, and sociality may not be as integral to their survival as it is for an individual in their prime," Marosi explained.
Meanwhile, younger sub-adults rarely visited the Reserve at all, sticking to near-shore habitats and river systems where they're safer from predation — including from adult bull sharks. The bolder youngsters who did show up had formed social ties with older sharks, who may act as mentors of sorts.
Why It Matters
"Contrary to commonly held perceptions of sharks, our study shows they have relatively rich and complex social lives," said Professor Darren Croft, from Exeter's Centre for Research in Animal Behaviour. "They likely gain benefits from being social — this may include learning new skills, finding food and potential mates while avoiding confrontations."
Understanding these social networks isn't just fascinating — it could help protect sharks. Marosi stressed that knowing how sharks relate to one another can inform conservation policy, and the Fiji Shark Lab is already working with Fiji's Ministry of Fisheries to apply the findings.
So next time someone calls a shark a mindless predator, you can tell them: actually, they've got a social life that would put most of us to shame. They've got friends. They've got frenemies. And apparently, they get a bit antisocial in their old age. Sound familiar?
