Sounding out the blue whale

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Copy of cw Antarctic blue 5 SUPPLIED The acoustics team in the sound lab aboard the Amaltal Explorer. Photograph: Melinda Rekdahl.

Cape Town - Blue whales are the biggest creatures known to have lived on Earth since its creation 4.54 billion years ago – and they are possibly also the loudest. Now, a team of Australian researchers has used the vocal ability of this iconic, but highly endangered, whale species to track its movements deep in the Southern Ocean and up to Antarctica’s icy edge.

Their fascinating results have proved conclusively that it’s not necessary to kill whales to learn about them, giving the lie to Japan’s continued claims for “scientific” lethal whaling.

Historically, there were hundreds of thousands of blue whales. These magnificent leviathans can reach 33m in length and weigh up to 190 tons, consuming as much as four tons of shrimp-like krill in a single day. In contrast, the largest-known dinosaur, Argentinosaurus of the Mesozoic Era, was estimated to have reached “only” 90 tons.

Blue whales were largely spared the ravages of early whaling because the whalers in their open rowing boots, and using hand-held harpoons, were simply unable to deal with the blues’ massive size and incredible swimming speed. Cruising the ocean at more than 8km/h, they can reportedly reach 32km/h when threatened.

But the writing was on the wall when Norwegian Svend Foyn perfected the exploding harpoon gun in 1868, and steam-driven whalers operating in tandem with factory ships started hunting in all the oceans of the world.

By the time blue-whale killing was officially banned in 1966 – the Soviets continued illegally into the 1970s – it’s estimated that as many as 330 000 had been taken in Antarctic waters, 33 000 in the rest of the southern hemisphere, 8 200 in the North Pacific and 7 000 in the North Atlantic. In just one season, 1930 to 1931, whalers killed 29 400 blue whales in the Antarctic region alone. This population, the largest, had been reduced to just 0.15 percent of its historic pre-whaling size and there were perhaps as few as 2 300 of them left.

Copy of cw Antarctic blue whale 10 An Antarctic blue whale and ice chunk in Southern Ocean. Photograph: Cath Deacon. SUPPLIED

Although the species is now recovering at about 8 percent a year, there are probably still only somewhere between 10 000 and 25 000 blue whales left worldwide, and looking for them in the vastness of the Southern Ocean down to Antarctica is real “needle in the haystack” stuff. Which is why Australian researchers decided to use the whale’s known vocal prowess as the key to tracking it.

Wikipedia reports that estimates made by two scientists in 1971 suggested that blue whales could produce sounds as loud as 188 decibels. National Geographic says this species emits a series of low-frequency “pulses, groans, and moans” and, in the right conditions, can hear one another up to 1 600km away. (Another source suggests up to 16 000km.)

Recently, Australian scientists undertook a seven-week research voyage to the Southern Ocean – the inaugural trip of the Antarctic Blue Whales Project that aims to estimate this species’s abundance, distribution and behaviour. The project is a flagship of the international Southern Ocean Research Partnership, involving 10 countries – South Africa, Argentina, Australia, Brazil, Chile, France, Germany, New Zealand, Norway and the US.

The 18-strong team of acousticians, engineers, whale-tagging experts and observers deployed passive acoustic “sonobuoys” – a portmanteau word from sonar and buoy – west of Antarctica’s Ross Sea area to locate blue whales. These buoys have hydrophone sensors, that relay underwater sounds via UHF/VHF radio to shipboard operators.

On the researchers’ return, lead marine mammal acoustician Dr Brian Miller explained that Antarctic blue whales had a very deep and resonating song that could be picked up hundreds of kilometres across the Southern Ocean.

“The acousticians made 626 hours (of) recordings in the sample area, with 26 545 calls of Antarctic blue whales analysed in real time. The researchers were able to triangulate the position of the whales from their vocalisations and direct the ship to the target area.”

A team was deployed in a small inflatable craft to gather skin biopsies (by shooting a small recoverable dart) and photo identifications from the whales.

“Whale tagger” Dr Virginia Andrews-Goff said researchers had also been able to deploy satellite tags on two blue whales.

“The tags transmitted never-before obtained data on rapid longitudinal movements during their summer feeding season and their foraging behaviour in relation to the edge of the Antarctic ice.

“This method of studying Antarctic blue whales has been so successful it will now become the blueprint for other whale researchers across the world.”

Australian Environment Minister Tony Burke said the researchers, working from small boats in freezing Antarctic conditions, had been “entertained and captivated” by the remarkable behaviour of the blue whales they’d encountered.

This non-lethal research method’s achievements clearly showed that it wasn’t necessary to kill whales to study them.

“This research reinforces Australia’s commitment to the non-lethal research of whales.”

During the voyage, scientists collected 57 blue-whale photo identifications and 23 biopsy samples, and attached satellite tags. They made 720 sightings of cetaceans (the collective word for whales and dolphins), including humpback, minke, fin and bottle-nose whales, and collected environmental data and Antarctic krill samples.

The results from the voyage would be shared with the IWC “to assist in the conservation and recovery of the Antarctic blue whale”, the Australians concluded. - Cape Argus

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