PREVIEW

BY MARK WORGAN

Humpback whales have been making record-breaking treks between breeding grounds in Australia and Brazil, according to scientists.

The whales were recorded for the first time crossing more than 15,000km (9,320 miles) of open ocean.

Researchers said the findings represented the greatest distances ever confirmed between sightings of individual humpback whales anywhere in the world.

The international team identified two whales that had been photographed in both eastern Australia and Brazil by comparing tens of thousands of images of whale tails, known as flukes.

“Discoveries like this are only possible because of investment into long-term multi-decadal research programmes and international collaboration,” said Stephanie Stack, a PhD candidate at Griffith University and co-author of the study.

“These whales were photographed decades apart, by different people, in opposite parts of the world, separated by two different oceans, and yet we can connect their journey.”

One whale was first photographed in Hervey Bay, Queensland, in 2007 and again in the same area in 2013 before later being recorded off the coast of São Paulo in Brazil in 2019.

Researchers said the two breeding grounds were separated by a minimum straight-line ocean distance of about 14,200km (8,820 miles) — roughly equivalent to the distance between Sydney and London.

Because scientists only documented the beginning and end points of the journey, the whale’s precise migration route remains unknown.

A second whale was first photographed in 2003 at Abrolhos Bank, off the coast of Bahia in Brazil, an important humpback whale nursery area.

More than two decades later, in September 2025, the same whale was spotted alone in Hervey Bay, representing a documented travel distance of 15,100km (9,380 miles).

Researchers said this was the longest distance ever recorded between sightings of the same humpback whale.

The study analysed 19,283 high-quality fluke photographs collected between 1984 and 2025 from eastern Australia and Latin America.

Images were contributed by both researchers and members of the public through the global whale tracking platform Happywhale.

Scientists used an automated image-recognition system to compare the photographs before independently verifying potential matches.

“This kind of research highlights the value of citizen science,” said lead researcher Dr Cristina Castro from Pacific Whale Foundation.

“Every photo contributes to our understanding of whale biology and, in this case, helped uncover one of the most extreme movements ever recorded.”

The researchers said such crossings appeared to be exceptionally rare.

Across more than four decades of data involving nearly 20,000 identified whales, only two individuals were found to have travelled between the two breeding grounds, representing about 0.01% of whales recorded in the study.

“Despite their rarity, these exchanges matter for the long-term health of whale populations,” Ms Stack said.

“Occasional individuals moving between distant breeding grounds can help maintain genetic diversity across populations and may even carry new song styles from one region to another – humpback whale songs are known to spread culturally across ocean basins, much like music trends in human populations.”

The team said the findings also supported what scientists refer to as the “Southern Ocean Exchange” hypothesis.

This theory suggests humpback whales from different breeding populations occasionally meet on shared Antarctic feeding grounds before some individuals return along entirely different migration routes to new breeding regions.

Researchers added that climate-driven changes in the Southern Ocean, including shifts in sea ice and Antarctic krill populations, could make such long-distance crossings more common in future.

The study, titled First evidence of bidirectional exchange between distant humpback whale breeding populations in eastern Australia and Brazil, was published in Royal Society Open Science.