A grey whale is believed to have set the longest migration record for a mammal – excluding humans – after swimming halfway round the world.
The lone whale piqued scientists’ interest after it was spotted off the coast of Namibia in south west Africa in 2013.
Though grey whales’ have occasionally been spotted in the Atlantic Ocean after leaving the North Pacific Ocean, none had ever been seen in the southern hemisphere before.
The location of the whale meant it had swum at least 20,00km (over 13,000 miles).
The sighting raised the question of whether the decline of whaling meant the recovering population could be attempting to re-establish old migratory routes or attempting to reach long-disused breeding grounds.
Researchers at Durham University in the UK examined tissue samples collected from the whale’s skin and analysed its DNA to trace its origins.
They found that the whale, a male, was most likely from an endangered North Pacific population, thought to include just 200 individuals, found along the coast of eastern Asia.
Professor Rus Hoezel, from the University of Durham’s department of biosciences told the New Scientist: “This is the record really for an in-water migration, if you’re assuming that this individual started its life in the north-west Pacific and it found its way to Namibia.”
“That’s as far as any vertebrate has ever gone in water, as far as we know.”
In comparison, the Arctic tern has the longest-distance migration of any bird, and covers a similar distance to the lone grey whale, as they move from their Arctic breeding grounds to Antarctic non-breeding areas, covering around 22,000km.
The researchers said the confirmation of the whale’s origin “contributes to our understanding of Atlantic sightings of this species known primarily from the North Pacific, and could have conservation implications if grey whales have the potential for essentially global dispersion.
“More broadly, documenting and understanding rare extreme migration events have potential implications for the understanding of how a species may be able to respond to global change.”
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