Humpback whales travel thousands of miles to mate

A new study published in the journal Biology Letters has found that some humpback whales (Megaptera novaeangliae) travel extremely long distances in search of mates during their breeding season. Moreover, while scientists previously presumed that whales which assemble on winter breeding grounds in Mexico and Hawaii are seasonally isolated, the new findings suggest that whales in these two winter assemblies may mix during one winter season.

By analyzing the Happywhale database, which includes photos of over 26,000 individual humpback whales taken since 1977, a research team led by Whale Trust in Hawaii found that two distinctive male humpback whales swam thousands of miles in search of partners during their mating season. 

While the first whale traveled 2,824 miles (4,545 km) from Maui, Hawaii to the Revillagigedo Archipelago of Mexico between 23 February and 17 April 2006, the other made the opposite journey, travelling 3,693 miles (5,944 km) from Guerrero, Mexico to Maui between 16 February and 5 April 2018. Moreover, both whales have also been spotted in northern feeding grounds off Alaska and Canada during the summer months.

Although on average, humpback whales swim at speeds of around 2.5 mph, to complete their journeys in the time they did, the two males must have been swimming much faster than this.

“Our first reaction was, ‘You’ve got to be kidding me!’” said study lead author James Darling, a researcher at Whale Trust. “They might just be traveling the ocean like it’s their own backyard.”

According to Darling and his colleagues, females may also be making these mammoth journeys. “If the males were out there following females, it would make more sense than them out there by themselves swimming for 40 days sans females during the breeding season,” explained Darling.   

Overall, the findings suggest that, contrary to previous opinions, there aren’t distinct humpback whale populations in the north-east Pacific. The sighting of the two males in both Mexico and Hawaii, “combined with other lines of evidence on Mexico–Hawaii mixing, including interchange of individuals year to year, long-term similarity of everchanging songs, one earlier same-season travel record, and detection of humpback whales mid-ocean between these locations in winter, suggests reassessment of the ‘distinctiveness’ of these populations may be warranted,” the authors concluded. 

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By Andrei Ionescu, Earth.com Staff Writer