Beached whales back in the swim thanks to new rescue technique
The new method, in which nets were positioned under whales with the help of jet-propulsion powerboats, was used for the first time last week to free seven of the creatures from a sandbar at Strahan on Tasmania's rugged west coast.
"It relies on having the right nets, the right boats, and also there's a risk of entangling the whales in the nets," Rosemary Gales, who led the rescue, said. "These are potentially quite dangerous operations."
Sperm whales of up to 50 tonnes are often stranded in Tasmania.
"We get to practise," Ms Gales, who works for Tasmania's department of primary industries and water, said. "There doesn't seem to be an equivalent in the northern hemisphere of the real hot spot we have here in Tassie," she said.
Smaller stranded whales are relatively easy to rescue. But for the sperm whale giants, jet boats are used to dig holes around the semi-submerged animals. Nets are then brought in to pull the whales into the holes and into increased flotation. "It's a power thing, really," Ms Gales said. "The jet boats we were using were about 350 horsepower. They can achieve very shallow draft, and there's no props, so there's no risk of injuring the animal."
In the past, little could be done to save stranded sperm whales. However, this is the third time the technique has been used successfully - each of them in Tasmania - and the first time it has been used on more than one animal.
The victims of single strandings are usually old, sick whales, or young animals which have made a mistake.
Mass stranding hot spots seem more likely to be caused by the shape of the sea floor. Tasmania's north-west coast is very tidal, which can take an animal from safe, deep water to a stranding in a matter of hours.
Big seas on Tasmania's west coast may also deposit so much material in the water that it interferes with whales' sonar and echo-locations, Ms Gales said.
Other theories put forward have blamed the earth's magnetic field and other magnetic fields created by man-made cables and the like. Some say noise may affect whale acoustics.
For some species with strong social bonds, when one strands, the rest follow. Ms Gates said: "Who knows what they're thinking. Are they stupid or incredibly wonderful?"
GRIM TOLL'S SUDDEN RISE
ABOUT 30 whales are reported stranded in Tasmania each year. At an average of one every 12 days, this is more than the other two hot spots, New Zealand and the North Sea. The Western Isles have the highest number for Scotland, with the Firth of Forth and the coastal area of Aberdeen second and third.
Accounting for 80 per cent of whale mass strandings in Australia, Tasmania has been reporting sharply increasing numbers of strandings since the early 1980s. Nobody knows whether strandings are increasing, or whether only reports are rising.
According to the latest data, only around five strandings a year were being reported in Tasmania between the early 1900s, soon after whaling stopped, and the early 1960s. In the mid-1960s this shot up to around ten, then rose to 20 in the mid-1980s, and to around 30 from the 1990s on.