Climate Change Threatens Humpback Whales' Krill-Heavy Diet, Study Finds

A new study led by Dr. Jasmin Groß from Griffith University's Centre for Planetary Health and Food Security reveals that humpback whales in the southern hemisphere heavily rely on Antarctic krill for their diet. The research predicts that future climate change impacts could disrupt this vital food source, affecting the whales' migratory lifestyle.

The study analyzed fatty acids and stable isotopes from blubber and skin samples of five different humpback whale populations around the southern hemisphere. The results showed that all tested populations had a diet consisting mainly of Antarctic krill, which provides a high-fat content diet ideal for their migratory lifestyle.

Dr. Groß warned that "the migratory lifestyle of humpback whales requires predictable ecosystem productivity, and so, we can expect that populations feeding in areas that are subject to the strongest climate change impacts are more likely to show the first signs of a departure from their high-fidelity krill diet."

Why this matters: Climate change's impact on humpback whales' diet has significant implications for the entire ecosystem. If krill populations decline, it could have a ripple effect throughout the food chain, leading to unpredictable consequences for marine life and potentially even human communities that rely on these ecosystems.

The study's methodology involved collecting blubber and skin biopsies from humpback whales in August and September 2019 in or near their respective breeding grounds off Brazil, Western and Eastern Australia, New Caledonia, and Colombia. Krill samples were collected from feeding grounds onboard three different vessels between January and March 2019.

The research also highlighted that future reductions in sea-ice extent and duration, along with rising ocean temperatures, could impact the whales' feeding ecology. Dr. Groß noted that "at present, there is no evidence of a divergence from a high-fidelity krill diet, but the characteristic isotopic signal we discovered of whales feeding in productive upwelling areas or in the marginal sea-ice zone, implies that future reductions in sea-ice extent and duration, and rising ocean temperatures could impact their feeding ecology."

The study provides essential baseline knowledge to assess the extent of climate change impacts on humpback whales' feeding grounds in future studies. Dr. Groß's PhD research was conducted as part of the Humpback Whale Sentinel Programme, a key surveillance initiative of the Antarctic Monitoring and Assessment Programme (AnMAP). AnMAP is a joint initiative between the Scientific Committee for Antarctic Research (SCAR), the Arctic Monitoring and Assessment Programme (AMAP), United Nations Educational, Scientific and Cultural Organization (UNESCO), and Griffith University.

The study, titled "No distinct local cuisines among humpback whales: A population diet comparison in the Southern Hemisphere," has been published in Science of the Total Environment.

Key Takeaways

• Humpback whales in the southern hemisphere rely heavily on Antarctic krill for their diet.
• Climate change could disrupt krill populations, affecting whales' migratory lifestyle.
• Krill decline could have a ripple effect on the entire ecosystem and human communities.
• Sea-ice extent and duration reductions, and rising ocean temperatures, could impact whales' feeding ecology.
• The study provides essential baseline knowledge for assessing climate change impacts on humpback whales.