Scientists document longest-ever whale journeys across lifetime

The spotting of two monitored humpback whales off the coasts of Australia and Brazil marks the longest distance ever recorded by scientists for these mammals.

The mammals were monitored over several years as researchers tracked their movements across the world’s oceans. Details of the tracking were published this week in a paper in the UK’s Royal Society Open Science journal, Deutsche Welle reported.

One whale was first seen off Queensland on Australia’s east coast in 2007 and again in 2013. It later appeared near São Paulo, Brazil, in 2019 — a journey spanning roughly 14,200 kilometres between sightings.

The second whale was first observed off the coast of Bahia, Brazil, in 2003, and then, 22 years later, near Hervey Bay in Queensland — a distance of about 15,100 kilometres.

The study noted that researchers could not determine the whales’ exact travel routes or total distances covered, because the figures “reflect the separation between sighting locations rather than actual distances travelled, as photo-identification records only the endpoints of each individual's travel.”

Humpback whales inhabit oceans around the globe and undertake some of the longest migrations of any mammal. They are especially popular with whale-watchers because they often stay close to shore and are known for dramatic surface behaviours, including breaching and slapping the water with their fins and tails.

During warmer months, humpbacks spend much of their time feeding and building fat reserves to sustain them through winter.

The whales feed on krill and small fish in colder waters during the summer before migrating to warmer tropical regions — including waters off Brazil and Australia — to breed in winter.

“Resighting intervals of 6 and 22 years suggest that these are rare, possibly single-lifetime events rather than regular migratory shifts,” the study’s authors wrote.

Out of thousands of identified whales included in the research, only 0.01% were found to have completed such journeys. Still, researchers said continued international collaboration on photo-identification databases could help determine how common these crossings really are.

“Despite their rarity, these exchanges matter for the long-term health of whale populations,” said Griffith University PhD researcher and study co-author Stephanie Stack.

“Occasional individuals moving between distant breeding grounds can help maintain genetic diversity across populations,” she said.

Scientists suspect climate change and warming oceans could make these long-distance crossings more common in the future.

“Climate-driven changes to the Southern Ocean, including shifts in sea ice and the distribution of Antarctic krill, may be making such crossings more likely over time,” Griffith University wrote.

By Nazrin Sadigova