By Mike Foley
The iconic procession of humpback whales down Australia’s eastern seaboard is peaking earlier and earlier, likely because their epic migration cycle has been sped up by rising sea temperatures.
Humpback whales are frequently spotted travelling the 8000 kilometres between Queensland’s Great Barrier Reef, where they breed and raise babies, and Antarctica, where they spend most of their year feeding on krill.
Whales dancing off the coast of Lennox Head, in northern NSW.Credit: Danielle Smith
In the early 2000s, their return journey – with calves by their side – would peak in early October.
But, if you want to catch the spectacle, start whale watching early, said University of Queensland Associate Professor Rebecca Dunlop, lead author of a study that finds the number of humpbacks migrating south is peaking three weeks earlier than in 2003.
“My advice is to start looking in the first weeks of September to get the most of them,” Dunlop said.
Whales must feed for long enough in Antarctica to build fat and protein stores to power their breeding and travel to and from tropical Queensland.
Rising sea temperatures are putting pressure on the food web whales depend on.
Dunlop said there had been a pronounced decline in sea ice coverage, leading to less algae, which, in turn, means less food for krill, the tiny crustaceans whales feed on.
“Less available krill prior to the migration could be forcing the whales back to the feeding grounds earlier,” she said.
Humpbacks are best known for their majestic breaches, as the marine mammals – measuring up to 16 metres and weighing up to 40 tonnes – erupt from the sea and soar into the air.
Amid the worrying signs for the whales is a success story. After being nearly hunted to extinction by industrial-scale commercial whaling – causing east coast number to fall to less than 100 – the banning of the practice has meant there are now 40,000 humpbacks plying the coastline.
Two humpback whales breaching near Manly in Sydney earlier this week.Credit: Whale Watching Sydney / Ted Lamb
Dunlop said humpback whale migrations had been brought forward around the globe, with other studies confirming similar patterns in California, Western Australia and South America.
World Wildlife Fund Australia oceans campaigner Richard Leck said a string of marine disasters – including South Australia’s algal bloom – demanded a swift response from the federal government, which this week returns to Canberra for the first time since the May election.
Leck urged the Albanese government to commit to a more ambitious emissions reduction target and invest in ocean protection “to avoid the types of horrendous events like, is happening in South Australia at the moment”.
The government will face pressure over the marine heatwave in South Australian waters, that started in September last year and has decimated fish, sharks, rays, cephalopods and all manner of marine life.
Thousands of dead fish have washed up along the beaches of Adelaide.
The Greens have accused Prime Minister Anthony Albanese of a similar failure to Scott Morrison not meeting with fire chiefs before the 2019 Black Summer bushfires after his government rejected marine scientists’ funding request to grapple with the damaging phenomenon.
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