Updated

A large shiver of hammerhead sharks was spotted on Monday carrying out a rarely seen mating ritual half a mile off Australia's northern beaches.

The 17 sharks, some up to 13 feet long, were filmed from an Australian news helicopter.

Shark expert Hugh Edwards said the ritual had only been filmed twice before, once off Mexico and once off the northwest coast of Australia.

"It's exciting, it's mind-blowing, this is some of the best shark vision I have seen. It is a very, very unusual spectacle," Edwards said.

Hammerhead sharks are usually solitary animals and not seen in big groups.

"They were swimming in circles which we assume is a mating ritual. They certainly weren't hunting anything," Edwards said. "It's very unusual to see hammerhead sharks in a group and when they are it is regarded as a world-wide phenomenon.

"There are very few places in the world where it happens and nobody has ever heard of it happening off Perth before."

The mating behavior of the hammerhead shark can be violent, and scientists recently discovered the sharks can reproduce asexually as well.

Hammerheads are mostly found in tropical waters, and there has never been a recorded attack on a human by this species of shark.

The news team was flying over the coast looking for a 4m shark. Cameraman Paul Brown also captured images of a dolphin frolicking just a few meters from the hammerheads.

To watch the video of the mating dance, visit PerthNow.com.au.