Blue whale. Credit: Elianne Dipp, Pexels.
A startling revelation has been uncovered by a major six-year acoustic study published in PLOS ONE: scientists have confirmed that blue whales are growing silent.
The study, led by biological oceanographer John P. Ryan, monitored blue, fin, and humpback whale songs using an underwater microphone 3,000 feet deep off the California coast. The research began in 2015, right at the peak of a catastrophic marine heatwave known as ‘The Blob’.
What the whales are telling us
Marine heatwaves like The Blob – which spanned over 2,000 miles of the Pacific Ocean – devastated the marine food chain. Krill, the tiny crustaceans that blue and fin whales rely on exclusively, nearly vanished. Without food, the whales slowly stopped singing.
“Blue whale vocalisations dropped by nearly 40 percent,” Ryan told National Geographic, adding, “It’s like trying to sing while you’re starving” (National Geographic).
The peer-reviewed study noted that while humpback whales – who can switch between krill and fish – continued singing, blue and fin whales went quiet during food-scarce years. Their song detection correlated directly with krill population data and ecosystem stress indicators.
Why whale song matters
Whale song reflects foraging success, reproductive effort, and the overall health of the ecosystem. When blue whales are silent, it’s a signal the ocean’s balance is breaking.
These animals are long-lived and roam vast distances. That makes them “ecosystem sentinels,” as Oregon State ecologist Dawn Barlow described. When they go quiet, it’s not just their problem – it’s ours too (National Geographic).
Global warming
Across the Pacific, from California to New Zealand, the same pattern has been recorded: warming seas, fewer krill, and quieter whales. A 2025 study found that the average duration of ocean heatwaves has tripled since the 1940s. These events are now up to 5°C hotter than historic norms, with lasting effects on marine life.
During the COVID-19 lockdowns, ocean noise dropped dramatically as global shipping slowed. Whale activity increased.
“Animals changed their distribution and used the habitat differently when there weren’t humans in those spaces anymore,” marine biologist Kelly Benoit-Bird said (National Geographic).
Now, scientists are pushing for a global network of underwater listening stations. Passive Acoustic Monitoring (PAM) could help track ocean health more effectively than satellites. As PLOS ONE notes, whale song could be a powerful biological sensor for climate change, fisheries management, and ecosystem conservation.
With greenhouse gas emissions fuelling ocean heatwaves and pushing krill toward collapse, researchers warn we may be approaching a tipping point.
If whales – the largest, loudest, most wide-ranging creatures on Earth – start going silent, what does that mean for our future?
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