Almost 500 pilot whales have become beached on New Zealand’s remote Chatham Islands over two mass strandings, with an expected survival rate of zero.
Project Jonah, which specialises in the protection and conservation of marine mammals, reported that a second mass stranding of about 250 pilot whales had occurred on Pitt Island on Oct. 10.
This was around 40 kilometres (25 miles) south of the earlier stranding of another 215 pilot whales on Oct. 8.
The remote beaches of Chatham Islands are known for the presence of great white sharks that pose a risk to people who try to refloat the whales, as well as the whales themselves.
Dead whales and ones with open injuries could draw great whites and other predators to the area, heightening the risk of shark attacks to anyone who attempts refloating.
This means stranded whales that are still alive on discovery in the islands are always euthanised by New Zealand’s Department of Conservation (DOC).
“These mass strandings are distressing events, and while we always hope for surviving whales are able to be refloated, this wasn’t an option here,” Project Jonah wrote on a Facebook post after the first stranding. “Our thoughts go to the DOC rangers and the local community at this time.”
Whale strandings at the Chatham Islands are not uncommon. The largest recorded pilot whale stranding occurred at these islands and involved an estimated 1,000 whales in 1918.
DOC media adviser Brian McDonald told Stuff news that the whales would be left to decompose naturally.
“This decision is never taken lightly, but in cases like this, it is the kindest option,” he said.
Pilot Whales Are Known For Strandings
On its website, the DOC describes pilot whales as “prolific stranders” and that this behaviour was poorly understood.
“Most scientists believe that individual whales strand because they are diseased and coming to the end of their natural lifespan,” the DOC said.
“Another theory points to pilot whales’ highly sociable behaviour—when one whale loses its way and strands, its pod mates may swim to its aid.”
The stranding comes almost four weeks after another stranding occurred in Tasmania, the southern island state of Australia.
A 230-strong pod of pilot whales beached on Tasmania’s west coast, and rescuers managed to refloat all 35 surviving whales.
The remaining carcasses were disposed of by long lining them out to the deep ocean.
The Chatham Islands is located about 850 kilometres east of the main islands of New Zealand, with a total population of around 800 people.
Pitt Island, the second largest island of the Chatham archipelago, has a population of 40.