Scores of pilot whales dead in New Zealand stranding
Most of the marine mammals beached themselves over the weekend but rescue efforts were hampered by the area's isolated location, about 800 kilometres (500 miles) east of the South Island, the Department of Conservation (DOC) said.
Department biodiversity ranger Jemma Welch said 69 whales had already died by the time wildlife officers reached the beach.
Welch said the animals had to be put down "due to the rough sea conditions and almost certainty of there being great white sharks in the water which are brought in by a stranding like this".
She said members of the local Maori community had performed a ceremony to honour the spirits of the whales, which would be left to decompose naturally.
The causes of mass strandings remain unknown despite scientists studying the phenomenon for decades.
Theories include pod members following a sick leader ashore, shoreline geography that scrambles the animals' sonar, the presence of predators and extreme weather.