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| Dead pilot whales Kalapaki Beach. Credit: Author |
Whale strandings—like the one that killed five pilot whales
on an East Kaua`i beach last year--remain among the most mysterious of natural occurrences.
Kaua'i residents were traumatized the morning of Oct. 13,
2017, as glossy black pilot whales lay gasping on the sand at Kalapaki Bay.
When well-meaning citizens shoved them back into deep water, most returned to
the sand.
Boaters in canoes and power craft patrolled the bay, trying
to keep remaining members of the pod from stranding. Eventually, five big
whales were dead.
Seven strandings within the past week of more than 200
whales of several species in New Zealand and Australia has refocused attention
on marine mammal strandings.
In all those southern hemisphere strandings, as in the Kaua`i
stranding, the cause was not immediately apparent.
And in the Kaua`i case, despite intensive studies over a
full year, scientists have been able to identify no obvious trigger.
"We still have no smoking gun but we're still looking,"
said David Schofield, stranding coordinator for NOAA's Pacific Islands Regional
Office.
One of the Kaua`i animals, an older one, had signs of
degenerative disease in earbones, but that was unlikely a cause of stranding,
he said. One whale had about 10 pounds of marine debris in its gut, but that,
too, was not a likely cause, Schofield said.
When animals are diseased, they are often malnourished.
These whales weren't starved. There was fresh food in their bellies. There were
no obvious signs of disease identified in a well-staffed mass necropsy that
continued through the night of the strandings.
They weren't damaged by sonar: No sonar vessels were
operating in the area, and in any case, the necropsies found none of the kind
of inner ear damage caused by high-intensity sonar.
There were no signs of disease apparent within the first few
weeks after the stranding.
Muscle and organ samples were sent to specialized
laboratories, but tests for pesticides or rat killers like diphacinone were
negative. (Diphacinone was of interest because it had been used in a rat
control effort on Lehua Islet in the weeks before the strandings.)
Researchers are still working on laboratory studies of
possible contaminants in the whale tissues, and tissue samples remain in
storage.
"We keep the file open. As new science becomes available,
we may go back and look again," Schofield said.
A series of seven separate strandings by different whale
species in New Zealand and Australia—all within the past week--adds to the enigma.
Mystery is often the case in explaining whale strandings.
And it’s just as much a puzzle this week in New Zealand and Australia.
Within the space of seven days, whales drove themselves on five
separate New Zealand beaches from the North Island down to little Stewart
Island, which lies south of Aotearoa's South Island, and even to the remote
Chatham Islands, which lie in the Pacific east of New Zealand. And another two
species died this week on the same beach, but in separate strandings in southern
Australia.
Ninety pilot whales went ashore on the Chatham Islands today.
An estimated 50 were dead or in such bad shape that wildlife officials
euthanized them. A few were able to refloat themselves and may survive.
Four days earlier, 145 pilot whales went ashore on remote
Mason's Bay on Stewart Island. They were the same species as in the Kaua`i 2017
stranding. All the Stewart Island whales died on a beach so isolated that it is
only accessible by foot trail or by air. An aerial photo shows the one to
two-ton whales scattered by the dozens along the shore, like so many akule drowned
in a surround net.
On the North Island, 12 pygmy killer whales went ashore on
one beach this past week. A few were reportedly pushed back into the water and
may have survived, but at least half were dead. A sperm whale died on another
North Island beach, and a pygmy sperm whale on still another.
Meanwhile, in Australia, 27 pilot whales and a humpback
whale were spotted dead this week on a remote beach in Croajingolong National
Park, which is in Victoria, the southernmost district on the Australian mainland.
They were spotted by air. By the time wildlife officials
were able to get there, some of the pilot whales were still alive, but were so
severely traumatized that they were put down. The humpback seems to have stranded
earlier and was already dead, Australian wildlife officials said.
And once again, at this point nobody knows why. It is a long
distance between these locations. From Stewart Island to the northern beaches
of North Island is nearly 1,000 miles. From the Chathams in the Pacific to
Victoria in the Tasman Sea is 2,000 miles.
There are lots of theories, many being proposed without
evidence.
Folks looking for a common thread in the latest strandings have
suggested climate change, but that's a guess. And it wouldn’t explain that the
largest known stranding occurred a century ago. One thousand pilot whales
stranded and died in the Chatham Islands in 1918.
The New Zealand stranding response organization Project Jonah,
says it might be illness, parasites, pollution, injury from boat strikes, human
undersea seismic work or sonar, disorientation due to shallow waters, boat
noise, undersea volcanic or earthquake activity, and in some cases, simple
geological traps—whales swimming into a bay a high tide an being unable to
leave at low tide.
There is, in many of these cases, a kind of community unity.
Once one whale is in trouble, the others stay in support—even at the risk of
dying.
"Whatever the reason for the initial stranding, social
cohesion may result in mass beaching. Their strong social bonds may prevent
them deserting a helpless member. Going to their aid, these animals may then
also become stranded themselves," says Project Jonah.
Strandings occur seasonally in some parts of the world,
although not in Hawai`i. The stranding season is just beginning in the
Australia-New Zealand area. Schofield recalls working Cape Cod, where there was
also seasonality.
"In wintertime, when you saw certain tides, sea conditions
and moon phase, you could almost predict them," he said.
And even so, the causes remain a mystery.
© Jan TenBruggencate 2018
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