The pod of whales – all of them females – beached on tidal flats near Ardrossan on Yorke Peninsula, West of Adelaide. An eighth whale was coaxed back out to sea by trained Environment Department staff.

Investigators are pursuing several theories as to why the giant mammals died, including the possibility that the whales were hunting salmon and became stranded when the tide went out. Some have blamed seismic blasting in the ocean, while another possibility is that one of the whales had become ill.

“They’re very sociable animals,” explained Aaron Machado, from the Marine Wildlife and Rescue Organisation, talking to 891 ABC Adelaide. “If one of them’s sick, alienates themselves – as social as they are – they’ll all follow unfortunately, so there could have been a number of different issues that caused this stranding.”

One of the dead animals was a lactating female – raising the sad possibility that the eighth whale helped back out to sea may have been her calf.

The beached carcasses have been targeted  by illegal souvenir hunters who have used hacksaws to cut out teeth from the giant jaws under cover of darkness.

A bigger headache for local officials is how to dispose of the huge carcasses, which can weigh up to 50 tonnes. The blubbery remains could potentially pose a health hazard once they start to rot, but the cost of removal would be prohibitive for the council.

Dr Deb Kelly, of the South Australian Environment Department, told ABC News: “If we take them out and just dump them in the ocean we create a maritime shipping hazard. The idea of blowing them up – that’s been fraught with danger on so many occasions. Even if we did that then maybe we’re just putting shark bait all the way along a long area of coastline and causing more harm than good.”

She added that the possibility of leaving most of the carcasses where they were had not been ruled out. “If it is a fairly unused crabbing beach in the mud flats then maybe that’s okay,” she said.

“This is rare,” stressed Dr Kelly, quoted in the Daily Mail. “Unfortunately things like this have been happening for thousands of years.”

Sperm whales can grow to 65ft in length and may live to be over 70 years old. Its numbers are unknown, but are estimated to run into the hundreds of thousands.