April 2, 2009

Experts Blame Whale Beachings On Climate Change

Researchers say global warming is bringing food stocks closer to shore, causing the mass beaching of whales along Australia's coast, the AFP reported.

Last week, nearly 90 long-finned pilot whales and bottlenose dolphins were beached along the Hamelin Bay on Australia's west coast in the last month.

Experts say it took the total number of beached cetaceans in southern Australia beyond 500 in the past four months alone, including a single stranding of almost 200 on King Island.

The strandings seem to occur in 12-year cycles that coincided with cooler, nutrient-rich ocean currents moving from the south and swelling fish stocks, according to researchers tracking the beaching of whales in the region since 1920.

Corey Bradshaw from Adelaide University, the project's leader, said most of the time, the animals are simply trying to find food.

He told AFP that when you bring the sea dwellers closer to an area that could be dangerous because there's more food, it is normal to see these temporal peaks in strandings.

He said the current cycle last peaked in the 2004/2005 southern hemisphere summer, where researchers saw some 30 strandings in a period of weeks where 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 and the numbers again appear to be reaching a peak," he said.

He added that it was more likely that these kinds of oscillations during climate change will be more variable and cause more extreme conditions.

"Where you maybe get a really cold pulse once every ten 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.

Marine scientist Catherine Kemper Little said little is known about what causes whales to beach en masse, but the theories were almost endless.

She said only highly social species beached in groups and if one creature got into trouble or fled a predator such as a killer whale the rest would follow.

Kemper, who works at the South Australian museum, said 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.

One theory is that toothed whales lose their ability to navigate with echo-location and since the island of Tasmania, Australia's southernmost state, has a narrow continental shelf, it makes deep water close to the coast.

Kemper said that when a few of them come onshore the rest follow because of their incredible social bond.

Government scientist Nick Gales, who works for the Antarctic authority, said storm events could also impair navigation by stirring up sediment.

"This becomes incredibly confusing for animals that use sound in the water column to navigate in the shallower waters. There is no real way of predicting these (incidents)," he said.

He said the main advances in science have only attempted to deal with the animals once they were already ashore.

At least 11 of the beached animals that washed ashore at Hamelin Bay were released back into the ocean using cranes fitted with giant slings. The 3.5-ton mammals were then transported nine miles to a more sheltered harbor and released back into the ocean.

These ambitious whale rescues have only been attempted in Western Australia state three previous times, and Gales said it was the first involving the long-finned pilot species.

Just three out of the ten had a successful return to deeper waters, while the remaining seven were either euthanized or perished after re-beaching themselves.

The rescue operations' success rates often depended on the fate of the so-called "ringleaders," Kemper said. "Either they die and (rescuers) get them out of the way, or they get them alive and back out to sea."

Bradshaw said mass beachings still remain one of nature's great mysteries.

"There are reams of hypotheses, predilections and pet theories, most of them have absolutely no basis whatsoever. Let's face it, this is biological life, we're all prone to making mistakes," he said.


On The Net:

Adelaide University

Pilot whales

Bottlenose dolphins