Like Humans, Bull Sharks Have Complex Social Circles That Include Forming Friendships and Avoiding Rivals

Popular culture portrays sharks as silent, solitary predators, but a new study suggests they have a much richer social life than previously thought. The research, published in the journal Animal Behavior, found that sharks can even form social bonds with specific “friends”.

The work focused on a population of bull sharks in Fiji’s Shark Reef Marine Reserve.

“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 Natasha D. Marosi, a shark conservationist at Fiji Shark Lab and study co-author, in a statement.

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Common Shark Social Behaviors

Marosi and her colleagues observed 184 bull sharks over six years. They divided the fish into three age categories: sub-adult (not yet sexually mature), adult, and advanced-adult (post-reproductive).

While the sharks didn’t shoot hoops or go for a coffee together, the team did record instances of shark sociality. They recorded when sharks “associated” by staying within one body length of each other, and when they showed more refined interactions, such as parallel swimming or following each other.

These social behaviors were common between adult sharks, while sub-adult and advanced-adult sharks were less social. While both sexes preferred to socialize with females, male sharks had, on average, more connections. This included the close shark “friendship” between the male sharks ‘Big Poppa’ and ‘Sharkbite’, who followed and swam beside each other across the reef.

“We are only just beginning to really understand the social lives of many shark species. Just like other animals, they likely gain benefits from being social — this may include learning new skills, finding food and potential mates while avoiding confrontations,” said Darren Croft, a behavioral ecologist at the University of Exeter, who co-authored the study, in a statement.

Hanging With Someone Their Own Size

Sharks were most likely to interact with sharks who were the same size as them.

“Male bull sharks are physically smaller than females; thus, one potential benefit they may gain is by being more socially integrated; they are buffered from aggressive confrontations with larger individuals,” said Marosi.

Marosi theorized that older and younger sharks have quite different reasons for avoiding social contact. Older sharks are experienced hunters and may rely less on socializing for survival. Younger sharks rarely visit the reserve, preferring to stay closer to shore. These younger sharks may socialize less to avoid the threat posed by bulky adult sharks.

“We do have some bolder sub-adults at the Reserve, and they have established social ties with some of the adult sharks. These older individuals may act as facilitators for inclusion within the social network, and also possibly provide pathways for social learning,” added Marosi.

A Better Understanding of Shark Socialization

The team hopes that a better understanding of how sharks socialize can improve efforts to manage and conserve their populations. Areas like the Shark Reef Marine Reserve are integral to these studies, as protected areas where researchers can study large numbers of animals year-round.

“This study capitalises on data and knowledge from one of the longest-running shark ecotourism dive sites in the world. This offered a unique opportunity to observe the detailed behaviour of these individuals over many years, as they grow, develop and manage their social relationships,” said David Jacoby, an ecologist at the University of Lancaster and study co-author, in a statement.

Read More: How Have Sharks Been Able to Remarkably Survive Natural Disasters?

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