More than 50 pilot whales have died and authorities are racing to save dozens more after a mass stranding on a beach in Western Australia.

The pod was first spotted about 100 metres off the coast at Cheynes Beach on Tuesday, local time, tightly clustered in what witnesses say was an unusual sight.

Once the whales began beaching themselves on the shore, wildlife authorities launched an emergency response effort in a bid to save them.

Some 51 whales died overnight on Tuesday, with authorities trying to return the surviving 46 to sea on Wednesday.

Dr. Andrew Brownlow, director of the Scottish Marine Animal Stranding Scheme who recently responded to a similar incident on a Scottish beach, explains why an incident like this may have happened, and why rescuers are now fighting the clock.

Some of Australia's worst mass stranding’s have involved pilot whales - 230 beached themselves on Tasmania's coast in 2022, and 150 were stranded in Western Australia in 2018. (BBC)