Friday, November 30, 2018

Kauai pilot whale strandings punctuated by seven separate stranding incidents in a week down under

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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