Around 240 pilot whales have died in another mass stranding on New Zealand’s remote Chatham Islands, the government said on Tuesday, only three days after 250 pilot whales died on the same islands.
No rescue efforts were made for the in total almost 500 pilot whales because the waters in that area are full of sharks. Survivors were euthanised, New Zealand’s conservation department said.
On Friday, around 250 beached pilot whales were found at Chatham Island, and on Monday, three days later, the government said another 240 were reported on Pitt Island. The locations made a rescuing the animals impossible, authorities said.
“Due to the risk of shark attack to both humans and the whales, the surviving whales were euthanised by our trained team to prevent further suffering,” Dave Lundquist, a government technical marine advisor, told news agency AFP. “This decision is never taken lightly, but in cases like this, it is the kindest option.”
The pilot whales will be left to decompose naturally on site. In September, around 200 whales died on a beach on Australia’s remote island of Tasmania.
The cause of mass strandings is still unknown to scientists. There is a possibility that pods are getting off track after eating too close to shore.
Pilot whales are very social animals and can remain with pod mates when they wander into danger. In some cases, that happens when a sick whale swims to shore, and other pod members follow in an effort to help the trapped whale.
Other scientists believe gently declining beaches confuse the whales’ sonar, making them think they are in open waters.
Olaf Meynecke, a researcher at Australia’s Griffith University, said that pilot whales use sophisticated sonar to find prey and for orientation. Meynecke links whale and dolphin strandings to changes in electromagnetic fields.
“These changes can be caused by solar storms or earthquakes, but there is also a strong connection between active sonar, for example naval sonar, and dolphin strandings, including pilot whales,” he said.
Karen Stockin, a whale stranding expert at New Zealand’s Massey University, told Phys.org that whale strandings could become more common as human use of the ocean, shipping traffic, and chemical pollution all increase.