Like Us, Sharks Pick Who They Hang Around With

Long thought to be solitary creatures, sharks continue to surprise us, demonstrating complex social relationships much like humans. A new study in Animal Behaviour tracked 184 bull sharks over six years at Fiji's Shark Reef Marine Reserve and found the predators form lasting social bonds, with patterns that go beyond simply gathering where the food is. Using photo IDs and close-range observations, researchers recorded when sharks swam within a body length of each other and noted behaviors like parallel swimming and following to distinguish true interaction from coincidental proximity, per Nautilus. The data suggest sharks are choosing their company.

Adults mostly associated with other adults, and younger sharks kept closer to grownup mentors than to peers. Both males and females tended to spend more time with females, but males had more social connections, likely because they're smaller than females and can avoid aggressive interactions, lead author Natasha Marosi of the University of Exeter says in a release. Sharks mostly hung around others of a similar size. These patterns, the authors say, show "active social preferences," just like humans demonstrate through our best friends and the people we avoid. "These bull sharks are doing similar things," Marosi tells Nautilus. Scientists suspect the ties may help with sharing information, avoiding larger threats, or sizing up potential mates—adding another layer to what we know about shark behavior.