A study published Tuesday in Royal Society Open Science confirms for the first time that humpback whales travel between breeding grounds in eastern Australia and Brazil, crossing more than 8,700 miles of open ocean.
One of the two cases exceeds 9,300 miles, making it the farthest distance ever recorded between two sightings of the same whale.
Every humpback whale carries a unique pattern on the underside of its tail flukes — a combination of pigmentation and scars built up over its lifetime. This is the basis of photo-identification — photographing those markings and comparing records across distant regions — and it proved decisive in this case.
The team, led by Cristina Castro of the Pacific Whale Foundation and Stephanie Stack of Griffith University, processed 19,283 high-quality photographs collected between 1984 and 2025 from eastern Australia and Latin America.
The images were first analyzed by an automated recognition algorithm and then verified manually by researchers. The result: two whales had been photographed in both regions, on opposite sides of the world.
The Happywhale platform, which centralizes photo-identification records contributed by scientists and citizen scientists worldwide, was essential for cross-referencing catalogs spanning such vast distances in both space and time.
The Two Record-Breaking Cases
The first involves a whale first photographed in Hervey Bay, Queensland, in 2007, spotted again in the same area in 2013, and later identified off the coast of São Paulo, Brazil, in 2019. The minimum straight-line distance between the two breeding grounds is approximately 8,700 miles.
The second case is even more remarkable. This individual was first photographed in 2003 at the Abrolhos Bank — Brazil’s main humpback whale nursery off the coast of Bahia — amid a group of nine adults. Twenty-two years later, in September 2025, it was spotted alone in Hervey Bay, Australia.
The distance between the two locations exceeds 9,300 miles, setting a new record for the longest confirmed distance ever observed between sightings of a single humpback whale.
The exact route is unknown in both cases, meaning the actual distances traveled could be considerably greater.
Humpback whales are known for their fidelity to breeding grounds: year after year, they return to the same waters to mate and give birth. That is what makes these two whales so remarkable: switching breeding grounds across ocean basins is virtually unheard of. In over four decades of records covering nearly 20,000 identified individuals, only these two animals displayed this behavior, representing just 0.01% of the sample.
Still, the rarity of this behavior does not diminish its biological significance. Occasional movement between distant populations can help maintain genetic diversity among groups that would otherwise remain isolated. The researchers also note that these movements may help explain the cultural transfer of songs between Atlantic and South Pacific populations — a phenomenon that has already been documented in humpback whales.
The Southern Ocean Hypothesis
The study reinforces what scientists call the “Southern Ocean Exchange” hypothesis: the idea that whales from different populations meet on shared Antarctic feeding grounds during the austral summer, and that some individuals — on their way back — take a different route and settle in an entirely new breeding region.
The authors note that climate-driven changes in those waters — including shifts in Antarctic sea ice and the redistribution of krill, the whales’ primary food source — could make these crossings more frequent in the future.
The study is the result of decades of fieldwork through a collaboration spanning Australia, Brazil, Ecuador, and the United States, involving institutions such as the Pacific Whale Foundation, Instituto Baleia Jubarte, and the Universidade Federal do Rio Grande do Norte.
“These whales were photographed decades apart, by different people, on opposite sides of the world, and yet we can connect their journey,” said Stack.
The authors urge continued collaboration through global photo-identification platforms, describing it as the most practical way to detect trans-oceanic crossings and understand their implications for the long-term health of whale populations.
