How a warming climate will change the humpback whale's diet

A recent study has raised concerns about the impact of climate change on the diet of humpback whales in the southern hemisphere.

The research, led by a team from Griffith University, reveals that a warming climate could potentially reduce the availability of krill – a primary food source for whales.

Humpback whale diet

Humpback whales have a diet that mainly consists of small marine creatures, with Antarctic krill being a significant component. Krill are tiny, shrimp-like crustaceans that are rich in fats and proteins.

Humpback whales consume krill in massive quantities, especially during the feeding season in the Southern Ocean. This high-fat diet is crucial for building the energy reserves they need for their extensive migratory journeys.

Humpback whales also eat small fish such as herring, mackerel, and sardines, particularly when krill is less abundant.

The whales use a feeding technique called bubble net feeding, where they create bubbles to corral and concentrate their prey. This strategy makes it easier to gulp large amounts in one go. Bubble net feeding is highly efficient and allows the whales to consume substantial amounts of food in a short period.

The reliance on a krill-heavy diet means that humpback whales depend on the health and stability of the Southern Ocean’s ecosystem. Changes in sea-ice extent, ocean temperatures, and krill populations could significantly impact their feeding patterns.

Therefore, maintaining the ideal diet for humpback whales involves preserving the delicate balance of their marine environment.

Climate change and whale diet

The study was conducted by Dr. Jasmin Groß as part of her PhD work at Griffith’s Centre for Planetary Health and Food Security.

Dr. Groß analyzed fatty acids and stable isotopes from blubber and skin samples of humpback whales from five different populations around the southern hemisphere. These biochemical markers were compared to those found in their primary prey, Antarctic krill.

Despite distinct differences in the biochemical profiles among the whale populations, the research confirmed that all tested humpback whale populations primarily feed on Antarctic krill.

“The migratory lifestyle of humpback whales requires predictable ecosystem productivity,” Dr. Groß explained. “Populations feeding in areas most affected by climate change are likely to show the first signs of a shift from their krill diet.”

Departure from a krill diet

Currently, there is no evidence of a significant departure from the krill diet. However, the research suggests that future changes may disrupt the whales’ feeding patterns.

“The characteristic isotopic signal implies that future reductions in sea-ice extent and duration, and rising ocean temperatures could impact their feeding ecology,” Dr. Groß noted.

Extent of climate impacts on whale diet

Blubber and skin biopsies were collected from humpback whales near their breeding grounds off Brazil, Australia, New Caledonia, and Colombia. Krill samples were gathered from feeding grounds between January and March 2019 aboard three different vessels.

Dr. Groß emphasized the importance of this study in establishing a baseline for future assessments. “Confirming that each population followed a high-fidelity Antarctic krill diet provides essential baseline knowledge. This can be used to assess the extent of climate change impacts in the feeding grounds in future studies,” she said.

Monitoring whale health

This research is part of the Humpback Whale Sentinel Programme, a key surveillance initiative under the Antarctic Monitoring and Assessment Programme (AnMAP).

As climate change continues to alter marine ecosystems, studies like this one are crucial for understanding and mitigating its impacts on marine life.

The findings highlight the critical need for ongoing monitoring and research to ensure the protection of these delicate ecosystems and the species that rely on them. Continued efforts are vital to understand and mitigate the impacts of climate change.

AnMAP is a collaborative effort between the Scientific Committee for Antarctic Research (SCAR), the Arctic Monitoring and Assessment Programme (AMAP), UNESCO, and Griffith University.

Fascinating facts about humpback whales

Humpback whales are truly remarkable creatures known for their majestic behaviors and complex vocalizations. These giants of the ocean embark on one of the longest migration journeys of any mammal, traveling up to 5,000 miles each way to move between their feeding and breeding grounds. 

Interestingly, only male humpbacks sing, and their songs are a sophisticated sequence of moans, howls, and cries that can last for hours, varying and evolving over time. Each population of humpback whales has its own distinct song, which changes from year to year.

These whales are also famous for their acrobatics; they often breach the water and slap the surface with their fins or tails, behaviors thought to be forms of communication or just playful antics

The study is published in the journal Science of The Total Environment.

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