Stranded whales: Kiwi volunteers gave their best to save dozens of animals | Photo: Reuters

More than 600 pilot whales have stranded at Farewell Spit, Golden Bay, on New Zealand's South Island.

It was one of the most deadly mass strandings in the history of the country. Two large pods washed ashore with a 48-hour gap between each event.

Marine scientists still don't know why the pilot whales came ashore, but they believe the cetaceans could have been swimming away from sharks, and pushed into shallow waters.

And because whales send distress signals when beached, the first pod might have called more to the muddy and low tide areas.

Around 400 animals perished. The good news is that Kiwi volunteers managed to save dozens of whales by keeping them wet; a small fraction was able to self-rescue.

"The animals can only be moved while floating, so work is dependent on tides. While the tide is out, the whales are kept cool and maintained as much as possible in an upright position," explained Herb Christophers from New Zealand's Department of Conservation.

"They have trouble bearing their own weight and sometimes suffocate because of the position they find themselves in when stranded."

Whale strandings are not uncommon in New Zealand. These cetaceans belong to the dolphin family and are not listed as endangered.

The local authorities will have to move and bury the carcasses in the nearby sand dunes.