WELLINGTON: More than 50 beached pilot whales perished in New Zealand on Friday, the latest in a spate of mass strandings this week that experts have linked to rising ocean temperatures.

The dead whales were part of a pod of 80-90 whales spotted late on Thursday on the shore of remote Chatham Island, about 800 kilometres east of the South Island, the Department of Conservation said.

It is the fifth stranding in New Zealand in less than a week, including 145 pilot whales which all died after they beached last weekend at Stewart Island, off the southern coast of the South Island.

By the time rangers reached the latest group of animals early on Friday 50 had died, one remained stranded but alive and the rest had refloated themselves and returned to sea.

Department of Conservation manager Dave Carlton said the surviving whale was in poor condition and was euthanised.

“It was the most humane thing to do. This is always an awful decision to have to make,” he said.

Chatham Island was the scene of New Zealand’s largest recorded stranding in 1918, involving 1,000 whales.

In addition to the strandings at Chatham and Stewart Islands this week, a group of 12 pygmy killer whales also beached in New Zealand’s far north and a sperm whale and a pygmy sperm whale grounded themselves in separate incidents on the North Island.

The reason whales and dolphins strand is not fully understood but theories include sickness, navigational error, geographical features, the presence of predators, and extreme weather.

Karen Stockin, a marine mammal scientist at Massey University, said while whale strandings were relatively common in New Zealand, the cluster of incidents in such a short timeframe was unusual.

Published in Dawn, December 1st, 2018