The Fight for Food in a Warming World

Future climate change may threaten the krill-based diet of southern hemisphere humpback whales, impacting migration and survival.

Researchers at Griffith University have predicted that the diets of humpback whales in the southern hemisphere could be significantly impacted by future climate change. The study, led by Dr Jasmin Groß during her PhD at the Centre for Planetary Health and Food Security, analyzes the dietary habits of these marine giants and the challenges they might face.

Study Details

In their study, the researchers collected humpback whale blubber and skin samples in August and September 2019 in or near their respective breeding grounds off Brazil, Western and Eastern Australia, New Caledonia, and Colombia. They also collected krill samples from feeding grounds onboard three different vessels between January and March 2019.

The researchers then analyzed fatty acids and stable isotopes from the blubber and skin samples of the five populations and compared them to the samples of Antarctic krill, which are their main prey.

They found that despite distinct differences in the biochemical profiles among the populations, the diet of all tested humpback whale populations was Antarctic krill. This diet is rich in fat, which is essential for the whales’ migratory lifestyle, according to Groß.

Predictions of Ecological Impact

Groß explained, “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.”

“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,” she added.

Groß emphasized the importance of this study, explaining that the confirmation that each whale population follows a high-fidelity Antarctic krill diet could be used as baseline knowledge to assess the extent of climate change impacts in the feeding grounds in future studies.

Reference: “No distinct local cuisines among humpback whales: A population diet comparison in the Southern Hemisphere” by Jasmin Groß, Rita M. Franco-Santos, Patti Virtue, Peter D. Nichols, John Totterdell, Milton C.C. Marcondes, Claire Garrigue, Natalia Botero-Acosta, Fredrik Christiansen, Juliana Castrillon, Susana J. Caballero, Ari S. Friedlaender, So Kawaguchi, Michael C. Double, Elanor M. Bell, Ryosuke Makabe, Masato Moteki, Nils Hoem, Brian Fry, Michele Burford and Susan Bengtson Nash, 1 May 2024, Science of The Total Environment.
DOI: 10.1016/j.scitotenv.2024.172939

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.