Volunteers in New Zealand are racing to rescue survivors after more than 400 pilot whales beached themselves.
About 300 have already died at Farewell Spit, on the South Island, in one of the worst such cases in the country.
Hundreds of locals and conservation department staff have been trying to save the survivors since early Friday morning, and have formed a human chain to refloat the whales.
Scientists do not know what exactly causes whales to beach themselves.
But it sometimes happens because the whales are old and sick, injured, or make navigational errors particularly along gentle sloping beaches.
Sometimes when one whale is beached, it will send out a distress signal attracting other members of its pod, who then also get stranded by a receding tide.
The conservation department said it had received a report about a possible stranding on Thursday night, but did not launch the rescue operation until Friday morning as it was too dangerous to attempt a rescue in the dark, reported the New Zealand Herald.