Sat, Dec 01, 2018 - Page 6 News List

Experts tie whale strandings to ocean warming


More than 50 beached pilot whales yesterday perished in New Zealand, 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 to 90 whales that was spotted late on Thursday on the shore of remote Chatham Island, about 800km east of South Island, the New Zealand Department of Conservation said.

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

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

Department manager Dave Carlton said the surviving whale was in a poor condition and was euthanized.

“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 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.

While whale strandings are relatively common in New Zealand, the cluster of incidents in such a short time frame was unusual, Massey University marine mammal scientist Karen Stockin said.

Species such as pygmy killer whales and sperm whales did not normally beach, unlike pilot whales, which regularly wash up on New Zealand beaches in the summer months, she said.

Stockin, who is an expert consultant on strandings for the International Whaling Commission, said that it added to a string of strange whale behavior over the past year.

In addition to a rise in strandings, she said a number of species had appeared that were not normally seen in New Zealand waters, including gargantuan blue whales in the Hauraki Gulf near Auckland.

New Zealand is experiencing some of the warmest ocean temperatures on record, Stockin said, adding that she believed it was affecting whale behavior.

“We’ve had an unusual week, which we haven’t got to the bottom of, and it’s fair to say it’s been an entirely unusual year,” Stockin told reporters.

“I suspect a lot of that has been driven by the warmer sea surface temperatures that we’re seeing at the moment,” she said. “We definitely have a spike in temperatures, that’s likely affecting where the prey is moving, and as a consequence we’re seeing prey moving and [whale] species following.”

One reason for the rising ocean temperature was the naturally occurring El Nino weather pattern, but global warming caused by climate change might also be playing a part, she said.

“We certainly have the El Nino pattern in play, but the reality is I’ve no doubt it’s been further exacerbated by the potential global warming effect,” Stockin said. “So you’ve got a bit of both going on there... We can’t tease those things apart at this stage.”

New Zealand’s summer, the peak time for whales to beach, begins today and Stockin said more strandings were likely.

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