Centuries of industrial whaling left only a few hundred Antarctic blue whales alive, making it almost impossible to find them in the wild.

New research suggests the population may be recovering. Australian scientists and international colleagues spent two decades listening for their distinctive songs and calls, and have found the whales – the largest animals ever to have lived – swimming across the Southern Ocean with growing regularity.

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Analysis of thousands of hours of audio, collected with underwater microphones and secondhand military-issued submarine listening devices, suggests whale numbers are stable or on the rise, according to the Australian Antarctic Division senior research scientist Brian Miller.

“When you look back to before this work was started by the AAD, we really just had so few encounters with these animals – and now we can produce them on demand,” Miller said.

“We can tell you where they’re frequenting, we can tell you that we’re hearing them more often. So that’s progress.”

The whales were heard increasingly often in the Southern Ocean from 2006 to 2021, according to a new paper collating the findings of Australian and international researchers’ seven voyages across the period.

“Either they’re either increasing in number or we’re increasing in our ability to find them, and both of those things are good news,” Miller said.

The Antarctic blue whale nearly became extinct before whaling’s decline in the mid-20th century, with the most latest estimates from 1998 suggesting there were fewer than 2,000 alive.

Researchers have spent hours listening for repeating songs about 20 seconds long, termed Z calls, along with shorter, higher-pitched D calls, in an effort to track and study the critically endangered species.

“We think the message is: ‘I’m a blue whale, I’m here,’” Miller said.

“If you think about … us almost wiping them out, and extinction, then it becomes more poignant to think about them saying, ‘I’m still here, here I am.’”

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The scientists travelled nearly 150,000km across the Southern Ocean tracking the whales’ appearances around Antarctica. Other Australian researchers say the study’s geographical and temporal range provides a rare insight into the state of the species.

“This is the first indication of what’s happening with Antarctic blue whales … for a good 20 years,” said Prof Robert Harcourt, a marine ecologist at Macquarie University. “All of the earlier work was based back in the 1950s when we were killing them.”

A Griffith University whale researcher, Dr Olaf Meynecke, said: “Having so many years [of data] over several seasons … and then having it over thousands of kilometres – that’s really unique.”

The whales spend half the year in Antarctic waters but are global travellers – heading north towards Australia, South Africa, South America and even across the equator.

Their distribution means scientists around the world have been drawn to the project, which Miller hopes will be a step forward for the International Whaling Commission’s conservation efforts.

“Only an international collaborative effort is going to be able to piece together the puzzle of where they are and whether they’re recovering,” he said.

Source: theguardian.com