Volunteers and whale experts hoped high tide on Friday would enable 100 surviving pilot whales to escape the notorious sand spit without re-beaching.
The Department of Conservation (DOC) local manager Andrew Lamason said rescuers were preparing themselves mentally for the "possibility that we may have a re-strand this afternoon."
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Fathoming a whale's death
Unfortunate news
Why did 12 sperm whales end up on German and Dutch beaches last week? What caused them to die? An autopsy of the more than 10-meter-long (33-foot-long) carcasses is supposed to reveal answers.
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Fathoming a whale's death
Heavy burden
For the autopsy, the whales were transported from the beach to mainland Germany. "Difficult and fascinating at the same time," Almut Kottwitz - the deputy environment minister of the German state of Lower Saxony - told DW. A female sperm whale weighs 15 metric tons (16.5 tons), a male up to 60 tonnes. Even though the beached whales were still quite young, they had to be moved with cranes.
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Fathoming a whale's death
Getting to the skeleton
First, the whale's skin is cut into strips and peeled from the body. Preparers removed its muscles and ligaments, and gathered up the innards. "It cut me to the quick to see how these beautiful animals were being skinned and torn apart," an observer of the procedure told DW.
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Fathoming a whale's death
Museum as final resting place
One of the skeletons was brought to Giessen University. Visible here is the whale's jaw - the bones will be treated for display. Another skeleton will be exhibited at a marine museum in Stralsund.
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Fathoming a whale's death
Lack of food
Some of the beached whales seem to have been undernourished, the atopsies found. No wonder: sperm whales feed on giant squids. And these don't live in the North Sea. "Their stomachs and their bowels were entirely empty," Almut Kottwitz told DW, adding that undernourishment seems to be "at least one of the reasons why they died." When whales are hungry and weak, they can get more easily lost.
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Fathoming a whale's death
Too heavy for land
Others among the sperm whales, however, seem to have been well-fed before they ended up on the beach, Ursula Siebert of the University of Veterinary Medicine in Hannover told DW: "They still had undigested beaks of giant squids in their stomachs, and feces in their bowels." Once on the beach, their weight compresses their blood vessels and lungs, causing them to die.
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Fathoming a whale's death
Champions in deep-sea diving
Sperm whales are not made to live in the shallow North Sea. They mostly live thousands of meters under water. In the North Sea, their echolocation doesn't work correctly. "When they arrive at the North Sea, they don't have muchof a chance of finding their way out of it again," vet and zoologist Siebert said. Ultimately, they beach and die.
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Fathoming a whale's death
Mass beachings
A week ago, more than 80 short-finned pilot whales got stranded on the beach of the Indian state of Tamil Nadu. Conservationists managed to push some animals back into the sea, but most of them died. Fabian Ritter of the Whale and Dolphin Conservation estimates that thousands of whales beach every year.
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Fathoming a whale's death
You beach, I beach
The more socially minded a whale species is, the higher the number of whales that beach from that group. The long-finned pilot whale is one of these species, Fabian Ritter says. These whales have a very strong connection within their family group, or pod. "When the leader is ill or out of sorts, and swims onto the beach, the other group members follow - out of loyalty."
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Fathoming a whale's death
Too much noise
Conservationists warn that underwater noise is dangerous for marine mammals. "Whales have a very sensitive sense of hearing and communicate via sound with each other," Fabian Ritter says. "Loud noise such as from military exercises disorients them." Especially beaked whales are known to beach more often when there is too much noise underwater, Rittter says.
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Fathoming a whale's death
Is the sun at fault?
Solar winds disturb the Earth's magnetic field. Whales might get confused and beach more frequently, researchers found. At the end of December 2015 were three major solar winds, physicist Klaus Vanselow of Kiel University told DW. This might have led the 12 sperm whales to take a wrong turn into the North Sea - and end in death on its beaches.
Author: Brigitte Osterath
The pod of whales was first spotted swimming close to shore by a DOC ranger on Thursday evening.
Lamason told Radio New Zealand that the whales were just milling around offshore instead of heading out into the open Tasman Sea off Nelson province.
The whale charity Project Jonah said scores of volunteers turned up with wetsuits to stay warm. Road access was difficult along the curved 32-kilometer (19-mile) spit.
New Zealand's online news chain Stuff via its regional newspaper "Nelson Mail" said Thursday night's stranding was New Zealand's third worst on record.
In 1918, a thousand whales stranded on the Chatham Islands far to the east of mainland New Zealand. In 1985 about 450 whales stranded in the Auckland area.
The spit was the scene of a major stranding in 2015.
Pilot whales, which can reach a length of six meters (20 foot), are a common species in New Zealand waters.
ipj/gsw (AP, dpa)
