Around 100 out of the 200 pilot whales that stranded themselves on New Zealand's beach have died while conservation officials are racing against time to rescue the survivors.
Time is running out for the whales at Farewell Spit beach where dry and sunny conditions prevail, aggravating the dehydration and sunburn for the whales.
A last chance to refloat the whales will be with high tide, failing which the mammals may have to be put down. Even then, there is a chance they would be back.
This is the biggest beaching incident in 10-15 years. The region has seen eight such incidents in the past decade, including two within the space of a week in January last year.
The number of whales in a small area makes it dangerous for conservationists to get in and help.
Pilot whales can grow to about 20ft (6 metres) and are the most common species of whale in New Zealand's waters.
"Re-floating stranded whales is a difficult and potentially dangerous job ... community group Project Jonah has 140 volunteers in the Golden Bay area who are trained to do this and we're working alongside them," Department of Conservation spokesman Andrew Lamason said.
Lamason said it could take days to refloat the whales and even then there would be no guarantee they would survive.
"We've had plenty times in the past where the pods have gone out to sea and turned around and come back again," Lamason said. "We're preparing for a big few days."
Scientists are not sure about the reason for such beaching incidents, reports AFP.
It is suspected to be some aspect of the whales' compromised ability to use echo-location in shallow, gently sloping waters.
Pilot whales, which are among the largest of the oceanic dolphins, could have got stuck on the beach due to their highly sociable behaviour where pod mates swim to help a whale that gets stranded.
Farewell Spit, which is located in Golden Bay near Nelson, is notorious for whales who get hopelessly stuck in its extensive shallow waters. The region has seen many incidents of stranding over the years.