Humpback whales can travel thousands of miles deep underwater in an astonishingly straight line - and the sun, moon and stars may be why they never get lost.
Scientists used satellite technology to track 16 tagged whales as they migrated thousands of kilometres northwards from the South Atlantic and South Pacific - but could not work out how they manage to navigate their way through the ocean's turbulent waters with such accuracy.
But it has now emerged the huge mammals may use a combination of the sun's position, Earth's magnetism and even star maps to guide their journeys, which can up 10,000 miles long.
Experts say humpbacks never deviate more than about five degrees from their migration courses.
Most of the whales in the experiment, which were tracked between 2003 and 2010, maintained an almost dead-straight course, deviating by less than one degree - despite the effects of weather and ocean currents.
Writing in the Royal Society journal Biology Letters, Travis Horton from the University of Canterbury said: 'They are orienting with something outside of themselves, not something internal.'
Stunning: The chart shows the migration patterns of hump back whales which can be 10,000 miles long
Most long-distance travelling animals are believed to navigate using a compass based either on the Earth's magnetic field, or the position of the sun.
But neither method can account for the extraordinary navigational ability of humpback whales, said the scientists, and they suspect the mammals use a combination of all three to find their way.
They said the earth's magnetism varies too widely to explain the straight lines and solar navigation needs reference points not available in the water.
They wrote in the letter: 'It seems unlikely that individual magnetic and solar orientation cues can, in isolation, explain the extreme navigational precision achieved by humpback whales.
'The relatively slow movements of humpback whales, combined with their clear ability to navigate with extreme precision over long distances, present outstanding opportunities to explore alternative mechanisms of migratory orientation based on empirical analysis of track data.'
Humpbacks feed during the summer near polar oceans and migrate to warmer tropical oceans for the winter when
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