A humpback whale has travelled the longest distance recorded for any unaided mammal, swimming across nearly a quarter of the globe between two breeding grounds.
The female whale's incredible journey began off the coast of Brazil and ended at Madagascar, almost 6,200 miles away.
It was photographed there two years after first being identified by researchers on Abrolhos Bank, Brazil, in August 1999.
Scientists do not know whether the whale's epic trip was deliberate or the result of a navigational accident.
Humpback whales are known for long distance migrations, regularly travelling 3,100 miles between breeding and feeding grounds. However, these journeys generally take them north and south, not east or west.
Such a long trip between breeding areas is unexpected in a female, because it is more normal for male mammals to wander in search of mates.
The whale, known as Antarctic Humpback Whale Catalogue (AHWC) no 1363, was recognised by its distinctive markings.
It was originally one of a pair observed for about an hour off the Brazilian coast.
The animal then disappeared until it was photographed on September 21 2001 from a commercial "whale watch" tour vessel.
Researchers led by Dr Peter Stevick from the AHWC, College of the Atlantic, Bar Harbour, Maine, in the US, said the distance travelled by the whale was the "longest documented movement by a mammal".