Marine experts and volunteers camped overnight at Cheynes Beach, more than 450km southeast of Perth in Western Australia after the whales were found washed up near the beach.

“Sadly, 51 whales have died overnight after a mass stranding,” Western Australia Parks and Wildlife Service said in a statement.

“(We) are working in partnership with registered volunteers and other organisations to try to return the remaining 46 whales to deeper water during the course of the day.”

Pilot whales are notorious for their strong social bonds, so when one whale gets into difficulty and strands, the rest usually follow, according to marine experts.

Australia and neighbouring New Zealand are hot spots for mass whale strandings owing to large colonies of pilot whales living in the deep oceans surrounding both island nations, but the reason why they get trapped on beaches remains a mystery.