By Stephen Beech

Humpback whales lose more than the weight of two adult elephants during their annual migration, reveals new research.

They shed an average of 11,000 kilos (24,250 lbs) of blubber - more than a third of their body fat and equivalent to the energy obtained after feeding on 57,000 kilos (125,664 lbs) of krill - during their epic ocean-spanning journey, say scientists.

Researchers used drones to monitor the body condition of 103 adult humpback whales in the southern hemisphere during their "feast and fast" migration.

The team used data from the drone monitoring to determine the whales’ body conditions on their breeding ground in Colombia and on their feeding ground on the Western Antarctic Peninsula, a highly productive krill region of Antarctica.

Each adult whale lost

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