Australia: Country's largest mass whale stranding from above

More pilot whales were found stranded on an Australian coast Wednesday, raising the estimated total to almost 500 in the largest mass stranding ever recorded in the country.

Authorities had already been working to rescue survivors among an estimated 270 whales found Monday on a beach and two sand bars near the remote west coast town of Strahan on the island state of Tasmania.

Another 200 stranded whales were spotted from the air on Wednesday less than 10 kilometers (6 miles) to the south, Tasmania Parks and Wildlife Service Manager Nic Deka said.

About a third of the first group had died by Monday evening, and an update on the death toll and condition of survivors was expected later Wednesday.

Tasmania is the only part of Australia prone to mass strandings, although they occasionally occur on the Australian mainland.

Australia's largest mass stranding had been 320 pilot whales near the town of Dunsborough in the state of Western Australia in 1996.

The latest stranding is the first involving more than 50 whales in Tasmania since 2009.

Rescue crews remained optimistic about freeing more whales, officials said

Why the whales ran aground is a mystery.

The pod may have been drawn into the coast to feed or by the misadventure of one  or two whales, which had led to the rest of the pod following, officials said.

Marine scientist Vanessa Pirotta said there were a number of potential reasons that whales might become beached, including navigational errors.

"They do have a very strong social system, these animals are closely bonded and that's why we have seen so many in this case unfortunately in this situation," Pirotta told Australian Broadcasting Corporation.

And rescuing them doesn't always work "because they are wanting to return back to the pod, they might hear the acoustics for the vocalisations of the sounds that the others are making, or they're just disoriented and in this case extremely stressed, and just probably so fatigued that they in some cases don't know where they are, " she added.

In neighbouring New Zealand, more than 600 pilot whales washed up on the South Island at Farewell Spit in 2017.