It sounds like the most terrifying social event on the planet – lots of sharks coming together for a gathering.
According to a new study in the journal Behavioral Ecology and Sociobiology, sharks can have gregarious personalities which cause them to assemble no matter what environment they are in.
Some sharks, however, politely turn down invitations the join the party (as any sane one of us would), because it turns out that sharks can also be very shy.
Research led by the University of Exeter and the Marine Biological Association of the UK (MBA) has shown for the first time that individual sharks have social personalities, which determine how they interact with other sharks in the wild.
They did this by monitoring 10 groups of sharks in large tanks. The tanks contained three different habitat types, which the researchers considered likely to result in varying social behaviour.
All of the sharks belonged to the same species – the small-spotted catshark found throughout the northeast Atlantic and Mediterranean – so that comparisons would be fair.
By recording their social interactions, they found that no matter what the habitat they were put in, any one shark showed consistent behaviour by either forming groups with other sharks or finding camouflage on their own. This provides a strong indication of inherent personality traits.
"We define personality as a repeatable behaviour across time and contexts. What is interesting is that these behaviours differ consistently among individuals. This study shows, for the first time, that individual sharks possess social personalities,” said lead researcher Darren Croft.
Why might sharks have evolved different personalities? According to behavioural ecologist David Jacoby, it is because they evolved different methods of self-protection. "These results were driven by different social preferences (i.e social/antisocial individuals) that appeared to reflect different strategies for staying safe,” he said.
“Well-connected individuals formed conspicuous groups, while less social individuals tended to camouflage alone, matching their skin colour with the colour of the gravel substrate in the bottom of the tank."
Here's to hoping we come across a shy shark if ever stranded in the middle of an ocean.