Did a marine heatwave cause 7,000 humpback whales to starve to death?

A humpback whale, nicknamed Festus, who died near Glacier Bay in June 2016 during a marine heatwave in the north-east Pacific. Starvation was given as the primary cause of death. Photograph: Craig Murdoch, taken under authority of NOAA Marine Mammal Health and Stranding

In 1972, a humpback whale nicknamed Festus was first spotted off the mountainous coast of south-east Alaska. He returned each summer for 44 years, entertaining whale watchers, local people and biologists as he fed in the cold, nutrient-rich waters of the North Pacific before returning to Hawaii to breed during the winters.

But in June 2016, Festus was found floating dead in Glacier Bay national park. The primary cause of death was starvation, which scientists believe was likely caused by the most extreme marine heatwave on record. New research, published on Wednesday by Royal Society Open Science shows the humpback population in the North Pacific declined by 20% between 2013 and 2021 after warmer water upended the ecosystem.