Fifty-one pilot whales died Friday in a mass stranding in New Zealand, less than a week after 145 pilot whales and nine pygmy killer whales perished in two other unrelated strandings.
In the latest stranding, up to 90 pilot whales beached themselves late Thursday at Hanson Bay on the remote Chatham Islands, said the Department of Conservation.
When staff arrived, they found up to 40 of the whales had refloated themselves but another 50 had died on the beach. The department said one beached whale remained alive, which staff decided to euthanize due to its poor condition.
The Chatham Islands are about 800 kilometres (500 miles) east of New Zealand’s main islands and are home to about 600 people.
Last weekend, 145 pilot whales died on Stewart Island. By the time conservation workers arrived there, about 75 of the whales were already dead and they decided to euthanize the others by shooting them due to their poor condition and the remote location.
On Sunday, 10 pygmy killer whales were found stranded at Ninety Mile Beach on the North Island.
Despite the efforts of 200 staff and volunteers, who managed to refloat eight of the whales after transporting them to a beach where conditions were calmer, all but one of the whales ended up stranding themselves again by Wednesday. Those whales were also euthanised.
Dave Lundquist, a technical adviser on marine species, said in a video released by the Conservation Department that there was no evidence to suggest the strandings were linked.
"You’re talking about strandings across the entire breadth of New Zealand in a very short period of time, which naturally does cause everyone to reflect on whether those might have something to do with one another," he said.
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.
She also pointed out that 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.
Ms Stockin, who is an expert consultant on strandings for the International Whaling Commission, said it added to a string of strange whale behaviour 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.
Stockin said New Zealand was currently experiencing some of the warmest ocean temperatures on record and she believed it was affecting whale behaviour.
"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," she told AFP.
"I suspect a lot of that has been driven by the warmer sea surface temperatures that we’re seeing at the moment.
"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."