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Though humpback whales may appear serene and slow-moving, they undergo one of the most extreme weight-loss transformations in the animal kingdom—losing around 36% of their body weight in under two months. Remarkably, they manage this without the harmful tissue breakdown seen in other species during starvation. New research is now shedding light on the massive scale of this fat loss.
Tracking the Great Migration by Drone
A team from Griffith University in Australia tracked 103 adult humpback whales (Megaptera novaeangliae) using drones as the animals migrated across the Southern Hemisphere—from the frigid waters of the Western Antarctic Peninsula to breeding grounds near Colombia, covering roughly 5,000 miles (8,000 kilometers) in a single direction.
The scientists focused on how this long-distance journey altered the whales’ bodies and how they managed to survive by burning large amounts of stored blubber while remaining healthy enough for females to give birth upon arrival in tropical waters.
According to their findings, humpbacks shed an astounding 24,250 pounds (11,000 kilograms) of fat during this voyage—about the combined weight of two adult African elephants. And they do it all without feeding en route. To fuel such a feat, each whale needs to consume the equivalent of 125,700 pounds (57,000 kilograms) of krill beforehand—roughly 28.5 million individual shrimp-like creatures, enough to exceed the takeoff weight of an Airbus A320.
To put that into perspective, it’s akin to a 200-pound (90-kilogram) human losing over 70 pounds (30 kilograms) in less than two months—without any negative health effects.
Seasonal Feeding and Fasting Patterns
“Southern hemisphere humpback whales depend on Antarctic krill for their annual energy requirements, fueling their long migrations between feeding and breeding grounds,” explained lead researcher Alexandre Bernier-Graveline. “We found the whales were at their fattest in early autumn (March to May), and reached their leanest condition by late spring (August to December), revealing a dramatic seasonal shift in body composition.”
“Our research captures the extremes of their ‘feast and fast’ lifestyle and underscores the critical importance of Antarctic krill for their survival and migratory behavior,” he added.
This extraordinary fat-burning ability reveals important details about humpback whales’ metabolic efficiency and energy demands. The energy burned during their 6- to 8-week migration is comparable to all the calories an average person consumes over the course of 62 years.
Unlike humans, whales rely on blubber as a primary, easily accessible energy source, allowing them to fast without harming vital organs or experiencing system failure. However, this finely balanced system is under threat—largely due to climate change and human activity.
Climate Change and Overfishing Threaten the Balance
Melting Antarctic ice and ongoing overfishing have reduced krill populations, which not only affects whales but also other krill-dependent species like chinstrap and gentoo penguins. For massive creatures like humpbacks, which rely on millions of krill to store energy annually, the impact could be especially significant.
This study provides valuable insight into how humpbacks survive such epic migrations and highlights the ecological importance of krill (Euphausia superba) in their life cycle. It also showcases how emerging technologies—like drone-based photogrammetry—can offer new ways to observe and understand elusive marine mammals in the wild.
“By connecting the energy costs of migration and reproduction with krill availability, our findings give critical ecological context to how environmental changes—such as declining krill populations—might shape the future of whale populations,” the researchers concluded.
Read the original article on: New Atlas
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