Rising ocean temperatures in whale breeding grounds to Australia's north may be a factor in Humpback whales leaving calving nursery regions too early in historic migration cycle

Research Gate

Southern Ocean humpback whales are shifting to an earlier return migration, 25 July 2025:

Authors:

Rebecca A. Dunlop

Emma Gumley

Ella Holding McGrath

Michael Noad

ABSTRACT

The Southern Ocean ecosystem is undergoing unprecedented environmental changes, which have led to shifts in the primary food source of baleen whales, Antarctic krill. Additionally, many humpback whale populations have rebounded from near extirpation due to historical whaling, increasing pressure on now vulnerable krill populations. Since humpback whales rely on energy reserves built up during their feeding season to sustain them during migration, changes in their food supply are likely to influence their migration strategies. In this study, the timing of the ‘return to feeding grounds,’ or southern migration, of the eastern Australian humpback whale population was tracked over a 21-year period. Both land-based and acoustic surveys were used to estimate the timing of the migratory peak in southern Queensland, i.e., the week with the highest number of whales sighted or recorded. Land-based surveys recorded all whales, including females with newborn calves, while acoustic surveys recorded singing adult males. Both datasets revealed that the peak of the southern migration has shifted earlier by approximately three weeks from 2003 to 2024. Although this study does not establish causation, it highlights a strong correlation between changes in migratory timing and sea ice coverage in the whales’ Antarctic feeding grounds. The observed decline in sea ice area, combined with the large increase in the humpback whale population, are discussed as potential factors contributing to the shift in migratory timing.

The Australian east coast is one of three principal migration paths for whales travelling between Summer and Winter feeding and breeding grounds. 

The Northern Rivers premier masthead expands on the subject.....

ECHO, 12 September 2025:

Decades of surveys show whale migration shift

As we near the end of the 2025 humpback whale migration, both north and south, a University of Queensland survey has revealed the peak of the southern migration of humpback whales down the east Australian coast is now weeks earlier than it was 21 years ago, and a warming Southern Ocean may be the reason.

Associate Professor Rebecca Dunlop from UQ’s School of the Environment found the return migration from northern breeding grounds has shifted earlier by approximately three weeks.

‘Acoustic and visual surveys show the peak of the southern migration in 2003 was in early October but by 2024, we observed it was in the middle of September,’ said Dr Dunlop.

‘While migratory timing naturally fluctuates from year to year by about two weeks, since 2021 there has been a clear and sustained change.’

The cues for migration are not well understood but are likely to be influenced by ecological and environmental factors impacting summer feeding while in the Southern Ocean.

Sea ice and krill populations

‘A big factor is the connection between sea ice and krill populations.’

Apart from the odd temporary stopover, humpback whales do not eat during the winter months when they migrate to tropical and subtropical breeding grounds.

‘Whales likely time their migration to ensure their stay in Antarctic waters is long enough with adequate feed to build the fat and protein reserves needed to fuel their journey to and from the breeding grounds, as well as for reproductive activities,’ said Dr Dunlop.

‘The later years of this study coincide with a pronounced decline in sea ice coverage beyond usual annual fluctuations.’

‘Less sea ice, or a shorter ice season, means less algae which is crucial food for krill.’

‘Less available krill prior to the migration could be forcing the whales back to the feeding grounds earlier.’

Population grown from 300 to 40,000

The eastern Australian population of humpback whales has grown from only 300 in the 1960s after sustained hunting, to around 40,000.

‘We did consider if an earlier departure from the northern breeding grounds could be driven by crowding or even human activity in the Great Barrier Reef,’ said Dr Dunlop. ‘But while the whale population increased steadily over the 21 years of this study, a clear shift in migration timing did not occur until after 2021 when rising water temperatures driven by climate change affected sea ice coverage in the Antarctic oceans.’

This earlier return south is also being seen in other humpback populations – along Australia’s west coast and South America.

‘I am concerned at some point we may see a decline in birth rates because females won’t have the energy to support migrating north, giving birth and getting their calf back to the feeding grounds.’

A research project is underway to determine whether the timing of the migration north away from the feeding grounds has also shifted. 

NOTE: My yellow highlighting in this post

As the gentle giants pass by......

Twice a year the ocean off the NSW Coast becomes a busy highway.

Between May and July these gentle giants can be seen heading north towards their sub-tropical breeding grounds and then between September and November they pass along coastal waters heading south back to Antarctica. 

Here are some scenes of the northern migration in 2023 and 2024 as the whales make their way through the waters off northern New South Wales.

 

Video by  Joe Young

 

pic.twitter.com/yJ6rjhztmp

— sᴉɹɹǝℲ ǝllǝɥɔoɹ (@OzEcology) June 12, 2024

Via @OzEcology

 Video byByron-Jindabyne

Video by Alex McNaught

Southern Right Whale and her small 'white' calf spotted in NSW coastal waters on their way to Antarctica

 

Southern Right Whale & her white calf
IMAGE: Right Whale ID program volunteer drone operator Maree Jackson

NSW Dept. of Planning and Environment, media release, 12 August 2022:

LEAVE THE LITTLE ‘WHITE’ WHALE ALONE

Four pairs of mother-and-calf southern right whales have been seen in NSW waters so far this winter – but one pair is slapping up a frenzy on social media.

The calf in this pair is mostly white, as seen in vision taken from high above, reminding people of the famous humpback Migaloo.

However, National Parks and Wildlife Service (NPWS) Marine Wildlife Team Project Officer Andrew Marshall said while the sighting was exciting, whale fans needed to stay well clear of the family.

It is illegal to approach any closer than 300 metres when a calf is present, if you are on a vessel, including surfboards, paddleboards and kayaks. Drones must legally stay at least 100 metres above the animals.

“The calf appears to be white but is actually brindle,” Mr Marshall said.

“Its ‘white’ areas will darken to grey as it ages – it’s one of around 1-in-30 southern right whale calves born with brindle colouring.

“This is a rare event to see a virtually white brindle calf, as southern right whales are mostly very dark, although some have splashes of white called a blaze.

“If you look closely at the video you can also see pale grey areas on the mother, who also carries the recessive brindle gene,” he said.

The vision was captured off the south coast recently by accredited drone volunteer, Maree Jackson, from the NSW Government’s Right Whale ID research program to monitor the whales.

Maree used her camera’s zoom function from above the legal height of 100 metres to capture the ‘white’ calf surfacing for a breath while swimming alongside its mother.

Her drone approached at 100 metres then used a 7x optical zoom to capture the stunning close-ups.

“Curious onlookers are reminded to keep back and give the nursing mother and calf space to rest undisturbed,” Mr Marshall said.

“A calf needs up to 300 litres of milk a day to gain the weight needed for the 5000-kilometre swim back down to Antarctic waters in the coming month, so both the mother and calf need to be left alone so they can rest and feel safe.”

Now in its second year, the Right Whale ID Program uses highly trained volunteer drone operators to photograph the unique white head-markings on each southern right whale.

The Right Whale ID program operates as part of the Marine Estate Management Strategy, working with volunteer drone operators to collect important information about southern right whales to assist in their management, protection and conservation.

Southern Right Whale & her 'white' calf
Vision: Created by Right Whale ID program volunteer drone operator Maree Jackson

BACKGROUND

https://www.youtube.com/watch?v=HNiA9qdF9ZA

Australian east coast 'peak' southern whale migration underway but so far fewer whale sightings & fewer calves

ABC News, 19 September 2021:

The Australian coast is a busy route for whales during their annual migration north.
(Supplied: Go Whale Watching)

Queensland researchers say whale watchers have reported fewer sightings this east coast migration season.

But experts say there has been less traffic near popular beaches this year.

Griffith Centre for Coastal Management researcher Dr Olaf Meynecke said it's been an unusual season with whales remaining further out to sea.

"Very different to the last three years at least, because we've had the whales migrate quite far offshore," Dr Meynecke said.

"There's a lot less happening closer to the coast."

Dr Meynecke said the southern migration was now underway, with whales and their calves making their return journey.

He said pods had been more commonly spotted 10-to-15 km offshore.

"We've actually had less entanglements in shark nets and those entanglements usually happen when the whales are close to shore," he said.

"Of course the mums and calves usually come close to shore to rest.

"But there's not as many as we had last year and definitely not as many newborns.

"It's been a very different season."

Whales and their calves are currently on their return journey south along the east coast.(Supplied: Seaworld)

Dr Maynecke said the East Australian Current (EAC) - made famous by a certain clownfish - serves as a navigation tool for migrating humpbacks.

He said this year the EAC was further offshore which could explain why whales were too.

Ocean Analyst Lucinda Matthews from the Bureau of Meteorology said the EAC did appear to weaken along the Gold Coast in August and move slightly east.

"It's possible the whales are now staying offshore to stay in the maximum current available to hitch the best ride south," Ms Matthews said……

The East Australian Current begins at the point where the westward flowing South Equatorial Current splits into two. (Supplied: Bureau of Meteorology)

Government of Japan sponsored whalers finally leave the Southern Ocean

Nisshin Maru is seen after it returned to port in Shimonoseki, Yamaguchi Prefecture at the end of its final whaling voyage into the Southern Ocean Japan Times

ABC News, 2 July 2019:

Japan's factory whaling mothership, the 'Nisshin Maru' has scrubbed 'research' from its hull and set out to sea as part of the country's resumption of commercial whale hunting.

Amid international criticism, several vessels left ports across the nation for the first for-profit hunt in 30 years. But this time, they are only going to hunt whales in Japanese waters.

Last December, Japan quit the International Whaling Commission, the body responsible for protecting global whale populations.

That meant the country could return to commercial whaling, but Japan had to give up a legal right to its so-called 'scientific whaling program' in the Southern Ocean.

Last year alone, Japan killed 333 minke whales in the Southern Ocean in the name of science.

Exiting the IWC and giving up that Southern Ocean whaling program was a "stupid" decision according to Japan's former chief IWC negotiator Masayuki Komatsu.

"We should go because it's a common property of the ocean," Mr Komatsu said.

"The more Australia claims that it is their own territory and their own oceans, the more that Japan [should keep going] because Australia is a minority.

"Japan and the US and other nations — China and Russia — we are a majority," he said.

Australian Parliament, Senate Hansard, 4 July 2019, excerpt:

Whaling

Senator WHISH-WILSON (Tasmania) (12:05): I seek leave to amend general business notice of motion No. 10

Leave granted.

Senator WHISH-WILSON: I move the motion as amended:

That the Senate—

(a) notes that:

(i) Japan has turned its back on the international community by recommencing commercial whaling for the first time since 1988,

(ii) Japan has also turned its back on a rules-based order by leaving the International Whaling Commission (IWC) which has been integral to preventing some species of whales from becoming extinct,

(iii) Norway and Iceland have reduced commercial whaling in recent years in response to the negative impact it is having on tourism, and

(iv) whale watching is a viable business in many parts of the world, and that it is a much more sustainable business than killing whales; and

(b) condemns Japan, Norway and Iceland for their commercial whaling, and implores them to support whale watching rather than whale killing.

Senator DUNIAM (Tasmania—Assistant Minister for Forestry and Fisheries and Assistant Minister for Regional Tourism) (12:05): I seek leave to make a short statement.

The PRESIDENT: Leave is granted for one minute.

Senator DUNIAM: The Australian government is disappointed that Japan has resumed commercial whaling, following its withdrawal from the International Convention for the Regulation of Whaling and its decision-making body, the International Whaling Commission. Australia has publicly urged Japan to return to the convention and the commission as a matter of priority. The government welcomes Japan's decision to stop whaling in the Southern Ocean and its commitment to continue to cooperate with the commission. The government's position on whaling has not changed: we remain resolutely opposed to all forms of commercial and scientific whaling. Japan is well aware of our position.

Question agreed to.

The rare Omura’s whale

The New York Times, 22 March 2019:

An Omura’s whale in waters off Madagascar in the Indian Ocean. CreditCreditGabriel Barathieu/Biosphoto, via Alamy

Salvatore Cerchio stunned the small world of whale science in 2015 when he found examples of a new species in the wild for the first time. Now, he’s mapped the habitat of that species, called Omura’s whale after Hideo Omura, a prominent Japanese whale biologist.

The surprise in the new study, published in Frontiers in Marine Science, is that Omura’s whales, though little seen, are widespread across the tropical world.

Dr. Cerchio, a researcher with the New England Aquarium in Boston, found a population off the northwest coast of Madagascar, where he works, and compiled reports of sightings from Japan, Australia, Brazil and off the coasts of Indonesia, among others. In total, from photographs, audio recordings, museums and documents, he identified 161 accounts of Omura’s whales in 95 locales.

Scientists said the finding is a reminder of how little we actually know about what goes on in the world’s oceans….

Japanese researchers first identified Omura’s whales in 2003, based on a 1998 stranding in Japan and tissue from eight animals killed during Japanese scientific whaling operations in the 1970s. The Omura’s whales have relatively small bodies, distinct genetics and unusually shaped skulls, leading researchers to conclude that the new species had split off from its genetic cousins 17 million years earlier.

Omura’s whales are baleen whales, meaning they are filter feeders, and they can be identified by their asymmetric coloration. The right side of their jaws are white, with a swirling, smoky splash of light coloration and four bisecting dark stripes on the right side of their heads, and their backs are decorated with asymmetrical chevrons. They favor tropical environments more than most whales and don’t migrate, Dr. Cerchio said.

After publishing his 2015 paper, in which he described more than 40 whales seen in the wild and expanded their range beyond the Indo-Pacific, Dr. Cerchio said people sent him pictures of similar looking whales.

“Little by little it became clear that there were a lot more out there that could be researched and tallied,” he said.

At the urging of Bob Brownell, the paper’s senior author, Dr. Cerchio counted images he received, those he’d stumbled across on the internet, as well as sound recordings and historical sightings dating back to a 1955 magazine article from Hong Kong University that misidentified an Omura’s whale as an immature fin whale.

Bob Pitman, a scientist with the National Oceanic and Atmospheric Administration who was not involved in this research, said he was surprised to learn the scope of the species’ habitat. “I think most of us whale scientists expected that it would have a small, relatively localized population,” he wrote.

As Mr. Pitman noted, “if new whales are still being described, it means we are probably also losing species of animals that we never even knew existed.”

From September 2019 onwards underwater seismic blasts will rock the Great Australian Bight around the clock over a 30,100 sq kilometre area

ABC News, 15 January 2019:

Oil and gas testing is set to take place in the Great Australian Bight this year, after the national petroleum regulator granted permission to exploration company PGS.

Environmental groups have slammed the decision to allow seismic testing near Kangaroo Island and Port Lincoln, while the tuna industry has questioned whether it is even likely to go ahead.

Seismic testing involves firing soundwaves into the ocean floor to detect the presence of oil or gas reserves….

The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) granted permission for the testing to be done over a 30,100-square-kilometre area, located 80 kilometres from Port Lincoln and 90 kilometres west of Kangaroo Island.

The testing is set to take place between September and November.

The fishing industry has long had reservations about the impact seismic testing would have on the local tuna industry.

PGS has been ordered not to interfere with or displace pygmy blue whales, southern bluefin tuna, and southern right whales…..

The Wilderness Society has slammed the permit, saying the practice can deafen whales and even kill smaller marine animals.

"It's obvious that blasting massive amounts of noise constantly for months on end through a water column in a space where animals communicate and navigate and live by sound and sonar, it is obvious that this is going to have a terrible impact on those animals," the environmental group's Peter Owen said.

"I fail to see how you can actually approve this type of seismic activity in the middle of one of the most significant whale nurseries in the world.

"It's totally unacceptable."

The Greens say the seismic testing is the first step to drilling in the Great Australian Bight.

"Why on Earth would we be wanting to sink oil wells in the Great Australian Bight, put our marine life and beaches at risk and make climate change worse," senator Sarah Hanson-Young said.

"We've got to be getting out of fossil fuels and transitioning to a clean, green economy."

There has been little research into the impact of seismic testing in Australia, but Western Australian researchers have found noise from seismic air guns significantly increased mortality in scallops.

Commencing on or about 1 September 2019 for an initial period of 91 days a fofeign-owned PGS survey vessel will be operating sounding equipment 24/7 in the Bight at a seismic source pressure of est. ~2,000 pounds per square inch (psi) with the two or three arrays firing alternately every 16.67 to 25 m, each with a maximum volume of 3260in. (See Duntroon Multi-client 3D and 2D Marine Seismic Survey Environment Plan at pp.24-25).

This is what happened when such testing went ahead in the Atlantic Ocean……..

https://youtu.be/9CsHz3lesC4

Earthjustice is suing the federal government to prevent seismic testing in the Atlantic Ocean. The process involves the blasting of shockingly powerful seismic airguns every few seconds for hours or even days on end and can cripple or kill marine life in the search of offshore oil or gas deposits.

Earth Justice: because the Earth needs a good lawyer, 20 February 2019:

Earthjustice is challenging the administration’s actions in court, and on Feb. 20, we joined a coalition of other conservation groups asking a federal judge to block the start of seismic airgun blasting in the Atlantic Ocean until our case has been heard.

The tests, harmful in their own right, are just the first step in the administration’s broader plans to open up 90 percent of U.S. federal offshore waters to the fossil fuel industry, despite widespread opposition from Americans across the nation.

Japanese Government to withdraw from International Whaling Commission and recommence commercial whaling?

The Sydney Morning Herald, 20 December 2018:

Japan is to withdraw from International Whaling Commission by the end of the year, giving it the freedom to resume commercial whaling, Japanese news agency Kyodo has reported.

Kyodo quotes a government source as saying that Japan is unlikely to catch whales in the Antarctic Ocean after its withdrawal.

The government is considering allowing commercial whaling only in seas near Japan as well as the country's exclusive economic zone, the source said.

The decision will be announced by the end of this year, Kyodo said.

Humane Society International (HSI) said in a statement that, if the reports were confirmed, they would mark a welcome end to whaling in the Southern Ocean.

However, Nicola Beynon, from HSI in Australia, believes that Tokyo's decision to leave the rules-based order of the IWC would place Japans' North Pacific whaling program completely outside the bounds of international law.

She also fears that Japan may recruit other pro-whaling nations to leave the IWC, "leading to a new chapter of widespread and unauthorised killing of whales for profit".

"This is the path of a pirate whaling nation, with a troubling disregard for international rule. We're going to continue to press the international community to bring an end to the unjustified persecution of whales for commercial profit wherever it occurs," she said.

The IWC was established in 1948 under the International Convention for the Regulation of Whaling. Japan joined the organisation in 1951.

Kyoda News, 20 December 2018:

The following is a chronology of events related to Japan's whaling.

1948 - The International Whaling Commission is established under the International Convention for the Regulation of Whaling.

1951 - Japan joins the IWC.

1982 - The IWC adopts a moratorium on commercial whaling.

1987 - Japan starts hunting whales in the Antarctic Ocean for what it calls "scientific research" purposes.

1988 - Japan halts commercial whaling.

1994 - Japan launches research whaling in the Northwest Pacific.

2005 - Anti-whaling Sea Shepherd starts obstructing Japan's research whaling in the Antarctic.

2014 - The International Court of Justice issues an order to halt Japan's research whaling in the Antarctic.

2015 - Japan resumes research whaling in the Antarctic by reducing the number of whales it hunts.

September 2018 - The IWC rejects Japan's proposal to resume commercial whaling at an annual meeting in Brazil.

Dec. 20 - Japan's plan to withdraw from the IWC comes to light.

Japan has until 1 January 2019 to notify the International Whaling Commission of its intention to withdraw.