Knock-on effects: Experts warn climate change may increase the number of whales we find stranded.
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SYDNEY: Experts studying mass whale beachings on Australia's coast warn that these tragedies could become more frequent as global warming brings their food closer to shore.
Almost 90 long-finned pilot whales and bottlenose dolphins died after washing up last week at Hamelin Bay, on the country's west coast.
It was the second mass stranding in the last month, and took the total number of cetaceans - whales, dolphins and porpoises - to beach in southern Australia in the past four months beyond 500, including a single stranding of almost 200 on King Island.
12-year cycles
Researchers tracking the beaching of whales in the region since 1920 said strandings tend to occur in 12-year cycles that coincide with cooler, nutrient-rich ocean currents moving from the south and swelling fish stocks.
"These animals, most of the time they're trying to find food, that's what they do," said conservation ecologist Corey Bradshaw, from Adelaide University.
"If you bring them closer to an area that could be dangerous, simply because there's more food there than there normally is you'd expect to find these temporal peaks in strandings, and that's exactly what we've found," Bradshaw said.
The current cycle last peaked in the 2004/2005 southern hemisphere summer, said Bradshaw, when there were 30 strandings in a period of weeks and a new animal washed up every four days.
The total number of stranding events that summer was almost equivalent to those recorded for the entire previous year, he said, adding that the numbers again appeared to be reaching a peak.
Totally beached
"With climate change it is more likely that these kinds of oscillations will be more variable so you get more extreme conditions," he said. "Where you maybe get a really cold pulse once every 10 years it might happen every five years, and we're already seeing that."
"We could see more and more frequent strandings simply as a function of higher frequency [of] extreme events," he added.
Little is known about what causes whales to beach en masse, according to marine scientist Catherine Kemper of the South Australian Museum, who said the theories were almost endless.
Only highly social species beached in groups, she said, and if one creature got into trouble or fled a predator such as a killer whale the rest would follow. "If a few of them come onshore the rest follow because of this incredible social bond," said Kemper.
Geomagnetic interference from elements such as iron ore could also scramble a cetacean's sonar, and complex coastlines such as that of Tasmania could be difficult to navigate, said Kemper.
Storm events could also impair navigation by stirring up sediment, said government scientist Nick Gales, who works for the Antarctic authority. "This becomes incredibly confusing for animals that use sound in the water column to navigate in the shallower waters," he said.
Rescue efforts
Of the pod that came ashore at Hamelin Bay, 11 were released back into the ocean using cranes fitted with giant slings. Once lifted to a truck, the 3.5-tonne mammals were transported 15 km to a more sheltered harbour for release.
It was only the third time such an ambitious rescue of whales had been attempted in Western Australia, and the first involving the long-finned pilot species.
Only three managed to return to deeper waters, with the remaining seven either euthanised or dying after re-beaching themselves, including a female and her calf.
