Since the 1960s, blue whales in the eastern North Pacific have steadily lowered the pitch of their songs. Today their tones are about 31 percent lower than they were over 60 years ago. 

More recently, during the years spanning 2015 to 2021, blue whale song activity dropped by roughly 40 percent, especially during marine heat wave events that devastated krill, their primary food source

This dual trend, a long-term tuning shift alongside a short-term silencing, suggests that both changing climate and food stress are impacting these ocean giants in significant ways.