The sightings challenge current understanding of humpback whale migration routes and population separation and have spawned the theory known as the “Southern Ocean Swap.”
Scientists have documented the largest displacement ever recorded between humpback whale sightingsafter identifying two animals that traveled more than 15 thousand kilometers between the coasts of Australia and Brazil.
The extraordinary journeys, revealed in a new publication in the journal Royal Society Open Science, were discovered through decades of whale photographs and global collaboration between researchers, whale watching operators and citizen scientists.
Humpback whales are known for their long seasonal migrations between feeding grounds in Antarctica and breeding grounds in warmer coastal waters. However, recently documented routes between eastern Australia and Brazil are considered exceptionally rareas humpback whale populations are typically very loyal to their established migratory corridors.
The researchers identified the whales by comparing the distinct patterns and shapes found on the underside of their tail fins, which act as fingerprints for each animal. More than 19,000 photographs collected over 41 years were analyzed to confirm the correspondences, writes .
The study revealed that a whale photographed in Australia was later identified off the coast of Brazil, while another, first spotted in Brazil, was later located in Australian waters. The shortest estimated travel distances for these trips were approximately 14,200 and 15,100 kilometersrespectively, making them the longest known journeys between humpback whale sightings worldwide.
Cristina Castrofrom the Pacific Whale Foundation, one of the study’s authors, said the findings would not have been possible without international cooperation and public input.
“Each image can help connect sightings across years and oceans,” said Castro, highlighting the importance of platforms like Happywhale, a global whale tracking database that allows tourists, researchers and whale watching operators to upload photos.
One of the whales was first photographed in Hervey Bay, Australia, in 2007, and later identified off the coast of São PauloBrazil, representing a minimum travel distance of 14,200 kilometers over a period of six years. The second whale was first documented in Brazil in 2003, before being photographed in Australia more than two decades later.
Researchers say these movements challenge current understanding of humpback whale migration and population separation. Scientists believe the whales may have temporarily altered their migratory routes after encountering whales from other populations in shared feeding areas in Antarctica, a theory known as “Exchange in the Southern Ocean“.
Environmental changes and variable prey availability may also have influenced unusual travel.
Despite the record distances, the researchers highlighted that the displacements seem be extremely rare. The two whales are the only confirmed examples discovered among tens of thousands of individuals photographed over four decades of research.
