Skip to navigation | Skip to content


Aussie blue whales call Antarctica home

blue whale

Pygmy blue whales that feed off the coast of Australia could be increasing their numbers in Antarctica, say researchers (Source: Catherine Attard/Macquarie University)

Blue whales The largest animal on Earth is changing its ecology, say researchers, and it could be due to climate change or the effects of whaling.

Catherine Attard, a PhD student from Macquarie University in Sydney, and colleagues, report their findings in a recent issue of the journal Molecular Ecology.

"Our study has added an important piece to the still large and incomplete puzzle that is blue whales," says Attard.

Blue whales (Balaenoptera musculus) are the largest living animal on Earth, yet we still know very little about them.

"They move around internationally and live in the ocean so they are hard to study," says Attard.

In the southern hemisphere there are two subspecies of blue whale, the Antarctic blue and the pygmy blue.

According to historical whale catch data, Antarctic blue whales feed in Antarctic waters and, by and large, the pygmy blue whales feed in temperate waters off the coasts of Western Australia and Victoria. Both of them move closer to the equator to breed in winter.

But, now Attard and colleagues have found genetic evidence that challenges the current knowledge about blue whales.

The researchers carried out an analysis of 155 genetic samples taken from blue whales around Antarctica and 109 samples taken from blue whales around Australia.

"We found a greater proportion of genetically Australian pygmy blue whales off Antarctica than expected," says Attard.

The researchers also found hybrids of Antarctic and pygmy blue whales - the first evidence ever of hybrids between different subspecies of whales, says Attard.

But why would current genetic evidence suggest a greater proportion of pygmy blue whales in Antarctica than expected according to historical whaling data, collected between 1913 and 1973?

Climate change or whaling?

One possibility, says Attard, is that climate change is warming the oceans and allowing the warmer-adapted pygmy blues to move further south.

Other explanations could lie with the decimation of Antarctic blue numbers by whaling.

"We know they [whalers] caught a lot more Antarctic blues than pygmy blues. We know that Antarctic blues dropped to less than 1 per cent of their original numbers," says Attard.

She says this could have encouraged pygmy blues to move south and take advantage of this drop in competition for Antarctic krill.

Then again, says Attard, maybe the number of pygmy blues in Antarctica hasn't changed much, and their proportion has simply increased because of falling Antarctic blue numbers.

A matter of method?

Attard says the puzzling discrepancy could also be due to the very different methods involved in collecting genetic data and historical whaling data.

To check if the discrepancy was due to method differences, she and colleagues used the genetic data to back track in time to estimate the proportion of pygmy and Antarctic blue whales.

When they did this, they found that the proportion of pygmy blues agreed with the lower historical proportion indicated by the historical whale data, giving confidence that the difference they find today is real.

Attard says although blue whales are now protected, they are still recovering from the effects of whaling.

She says pygmy blue whales need to be managed differently to Antarctic blue whales and the findings should help in these efforts.

Tags: ecology, mammals-whales