Some 380 pilot whales have died after becoming stranded off Australia's southeastern island of Tasmania, up from 90 the previous day and setting a new record for the country, local media reported Wednesday.
"I can confirm that 380 whales are dead," rescue coordinator Nic Deka of Tasmania's Parks and Wildlife Service told ABC News.
Deka said rescuers have managed to save 50 whales from a sandbar on the island's west coast, at several locations near Macquarie Harbor, but some 30 others were still stranded and clinging to life while waiting to be pushed out to sea.
"This is definitely the biggest (pilot whale stranding) in Tasmania and we believe it's the biggest recorded in terms of numbers in Australia," Kris Carlyon, a wildlife biologist of the Tasmanian government's Marine Conservation Program, told ABC.
However, larger numbers have been recorded in neighboring New Zealand, with the biggest recorded stranding there being an estimated 1,000 pilot whales at the Chatham Islands in 1918.
Wednesday's grim discovery of 200 dead whales in shallow waters just off the coast brought the total number of whales involved in the mass stranding to more than 450.
Before their detection by aerial surveying, rescue crews were already racing to save as many as possible of 270 distressed whales discovered Monday just a few kilometers away.
In a Tasmanian government press release, Deka said local authorities are still considering how best to dispose of the hundreds of whales carcasses, each of which weighs approximately 3 tons.
"We can't leave the whales in the harbor as they will present a range of issues. We are committed to retrieving and disposing but our key priority is to remain focused on the rescue effort," he said.
Rescue efforts are being concentrated on whales assessed as having the best chance to survive, which are being towed into deeper water.
Carlyon told ABC that euthanasia was an option as more time passes.
Researchers are still trying to fully understand the behavior of pilot whales, including what causes them to get stranded in shallow water.
However, some scientists believe that as they are very social animals, when one pilot whale loses its way and becomes stranded, other members of the pod swim to its aid and become trapped themselves.
Another hypothesis is that pilot whales' echolocation is not well-suited to shallow, gently sloping waters, because they generally prefer steep areas such as the edge of the continental shelf. This would also explain why most mass strandings happen in summer, when the whales follow popular food sources inshore.