The longest journey of a humpback whale: Male travels over 8,000 miles to mate

Humpback whales are among the animals that travel the longest distances. They follow a pattern: they spend their mating and breeding season in the warm waters near the equator, and then travel thousands of miles to the icy seas of the Arctic and the Atlantic or the North Pacific or, in the southern hemisphere, those around Antarctica. There they feed on anchovy fry, herring or sardines or, in the Antarctic Ocean, on krill, a tiny shrimp-like crustacean. However, a group of marine biologists has reported in the scientific journal Royal Society Open Science the longest journey made by a specimen of this species that did not follow the pattern. A male sighted in the Pacific Ocean, off the coast of Colombia, was seen again near Zanzibar, in the Indian Ocean, some time later. There are over 8,000 miles between the two locations, both known mating areas. This migration exceeds by almost 2,500 miles the greatest distance recorded so far by these cetaceans.

Although there are birds capable of travelling between the poles and back in the same year, such as the Arctic tern, among mammals none travel as much as the humpback whale (Megaptera novaeangliae). Once abundant, intensive hunting over the course of centuries almost wiped them out. The ban in place since the 1960s is facilitating their recovery, although they now only number 5% of their historical total. Their distribution follows a seasonal movement: they spend the summer in the colder but richer waters of the north or south. With the arrival of winter, they migrate towards the equatorial or more tropical regions. Due to the hemispheric inversion of the seasons, populations in the northern hemisphere rarely overlap with those in the south. Migration is almost in a straight line, although it would be more correct to say that they move in the same longitude. Thus, the seven large populations identified by the International Whaling Commission in the southern hemisphere descend in latitude to their portion of the Antarctic Ocean when it is summer there. For example, the hundreds of specimens that court and mate off the warm coasts of eastern Colombia and Ecuador travel along the American continent until they reach the Antarctic Peninsula, which is just below them on the map. And when winter comes, the pregnant females return north to give birth and the males return to look for a mate. That is why what the whale registered as HW-MN1300828 did is so special.

“This whale [a male] was sighted off the coast of Colombia (twice) and then again off the coast of Zanzibar five years later, making it the longest recorded orthodromic distance [the shortest path between two points on a sphere] between breeding grounds for a humpback whale,” says Ekaterina Kalashnikova, a biologist at the Bazaruto Center for Scientific Studies (BCSS), which conducts ocean research in Mozambique and southeastern Africa. Measured in this way, this whale migrated at least 13,046 kilometers (8,106 miles) in a straight line on the sphere that is the Earth. Such a long migration has never been recorded among these animals. However, Kalashnikova, the lead author of this research, is convinced that its journey was much longer, but there is no way to prove it.

HW-MN1300828 was sighted by biologists in the Gulf of Tribugá, in the Colombian Pacific, in July 2013. It was seen again in the summer of 2017, 48 miles away, in Solano Bay, also in Colombia. In the Happywhale registry, a repository of sightings with data on thousands of whales, it does not appear again until five years later and very far away: on 22 August 2022, it was sighted again in the Zanzibar Channel, between Unguja Island and the mainland coast of Tanzania, in the south-west Pacific. The records are supported by photographs, in particular of the whale’s caudal fin, which functions as a fingerprint. “Each animal is identified by examining the posterior contour, pigmentation patterns, and other natural notches on the ventral part of the caudal fins,” explains Kalashnikova.

How did he get from Colombia to Zanzibar? The researchers don’t know. Most likely, on one of his annual trips south to the Antarctic Peninsula, something made him go east, along the coast of Antarctica and, at the height of the African cone, up to the Tanzanian coast. Although in theory he could have taken the opposite route, west, skirting the frozen continent in the opposite direction, there is an almost insurmountable physical barrier: the Antarctic Ocean is governed by the circumpolar current, the most powerful on the planet, which would make it very difficult to go against the current, when on the other side he would just have to go with the flow. On his return, logic also suggests that he ascended in a relatively straight line to African latitudes.

Kalashnikova recalls that the journey in this direction, from west to east, has been demonstrated by whale songs. Humpback whales are among the cetaceans with the most elaborate songs, and they even speak different dialects between different groups. Recent research has shown that the song, specific to each population, “evolves, since each year a new addition is added, which is often a fragment of the song of another population of humpback whales, and after a while the entire population begins to sing this slightly modified song,” explains the biologist. Scientists have verified how this evolution has an eastward direction, “which means that the same fragments are transferred from west to east through the populations; for example, in 2018 a new fragment was sung in Namibia and Mozambique, then, in 2019, that same fragment was detected in western Madagascar, and then in eastern Madagascar and Australia.” A yet-to-be-published paper now compares the songs of whales from Colombia and Zanzibar, precisely the journey of the male that broke the record.

The long journey of HW-MN1300828 exceeds by at least 3,715 kilometers (2,308 miles) the longest distance recorded between two sightings of the same humpback whale. The first time it was seen in January 1997, in the waters surrounding the Antarctic Peninsula, it was assumed that it came from the south-east Pacific, like our male protagonist. This was a female and, 15 years later, it was photographed again in Byron Bay, in eastern Australia. Whether it was coasting around Antarctica and then going up, or directly crossing the south Pacific, the mammal travelled 9,807 kilometers (6,093 miles) if it took the first route, or 9,331 kilometers (5,798 miles) if it took the second. At the time, either of the two was the longest distance recorded until then, 2012, by one of these cetaceans.

Jorge Acevedo, a cetacean expert from the CEQUA Foundation (Chile), was one of the authors of that research on the traveling female humpback whale. Acevedo, who has not been involved in the current work on the male, highlights in an email that “migrations or longitudinal movements of a few animals from one population to another can be said to not occur with high frequency.” The typical movement or migration, he recalls, “is the latitudinal one from the breeding area to the feeding area that each population has.” However, more and more longitudinal movements are becoming known in the southern hemisphere. In his opinion, it could be due “to the fact that humpback whale populations continue to increase, and perhaps these movements were more common before the whaling period.”

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