A team of Australian and New Zealand researchers has tracked scores of blue whales off Antarctica, eavesdropping as the world's largest animals began their rumbling song, which can be detected 750 kilometres (465 miles) away.
During the six-week Australia-New Zealand Antarctic Ecosystem Voyage to the Southern Ocean, which returned today, the Antarctic marine scientists listened for the low moans of the endangered whales, and then tracked them to their feeding grounds.
The scientists were able to identify 58 individual blue whales and record more than 40,000 calls during the voyage, which aimed to help estimate the population size of the endangered animals and their movements.
"What actually was remarkable this time was that very early on in the voyage there were very few calls and that made us nervous," the Australian Antarctic Division's Mike Double said.
Double thinks the animals were in the area all along, just not making any noise.
Double said the expedition had been hoping to see a small number of the blue whales and was thrilled when they came across about 80 in a small area after travelling a long way with no sightings.
They had noted their foodstuff krill was "really tightly aggregated into very dense swarms". "And we didn't really see that in other areas throughout the voyage," he said.
"It's not just about finding whales," voyage leader Richard O'Driscoll said of the mission, which also gathered oceanographic and atmospheric data.
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