An investigation into the energy consumption of humpback whales during their annual migrations revealed that they lose 11,000 kg of fat — equivalent to the energy obtained after feeding on 57,000 kg of Antarctic krill — highlighting the importance of managing their krill-rich feeding grounds.
PhD student Alexandre Bernier-Graveline, from Griffith University’s Southern Ocean Persistent Organic Pollutants Programme, led the study, using drones to monitor the body condition of 103 adult humpback whales in the southern hemisphere.
Bernier-Graveline and the research team used drone-monitoring data to determine the body conditions of the whales in their breeding grounds in Colombia and in their feeding grounds on the Western Antarctic Peninsula, a highly productive region of Antarctic krill.
Each adult whale lost about 36% of its body condition during migration, which equates to:
- 12 cubic meters or 11,000 kg of fat (equivalent to the weight of a typical single-decker city bus or two adult African elephants)
- 5,000 kg of fat
- 196 million kilojoules of energy (equivalent to the energy consumed by an average adult over 62 years old)
- 57,000 kg of krill
“Southern Hemisphere humpback whales rely on Antarctic krill for their annual energy needs, fueling their long migrations between feeding and breeding grounds,” says Bernier-Graveline.
“We found that the whales were fatter at the start of autumn — March–May — and leaner at the end of spring — August–December — showing a dramatic seasonal shift in body condition,” he adds.
The study quantifies the extreme feast-and-famine lifestyle of the whales and the crucial role of Antarctic krill in their survival and life-history migratory strategy.
Bernier-Graveline says that, with rapid changes in the Antarctic sea-ice ecosystem, understanding the energy needs of migratory whales has helped scientists assess how environmental changes — such as krill availability or climate change — could affect whale populations.
By relating migration and the energy cost of reproduction to krill biomass, the findings provide essential ecological contexts for understanding how environmental changes, such as fluctuations in krill populations, could affect whale populations in the future.
