Sharks are the first fish known to have networks of friends, just like mammals.

Contrary to the common belief that sharks are solitary animals, researchers at the University of Delaware found that sharks actually have thriving social networks.

Using acoustic tracking devices, the oceanographers followed over 300 Sand Tiger sharks and recorded their interactions over the course of a year.

They discovered that the sharks have complex social structures, akin to those of smart mammals such as dolphins, elephants and chimpanzees.

"Higher-order decision-making processes are often associated with mammals," said Danielle Haulsee, a PhD candidate at the University of Delaware. "Our research shows that it is important for the scientific community to not rule out these types of behaviours in non-mammalian species."