Blue whales are the largest animals on Earth, but researchers now worry about their survival as the giants grow quieter.
For ocean scientists, blue whale songs have long defined the soundscape of the seas.
Now concern is rising because the endangered species appears to be falling silent.
A study by the Monterey Bay Aquarium Research Institute found that blue whale song detections dropped by almost 40 percent over the past six years.
Despite their size, blue whales mostly eat krill, and they’ve even been seen protecting people from shark encounters on occasion.
Blue whales have existed for millions of years but were hunted almost to extinction in the 1900s.
Hunting these whales was banned in 1966, yet they remain endangered, and observers say human-driven climate change may be reducing their numbers and songs.
David Attenborough has repeatedly warned about the ocean’s future (Dave Benett/Getty Images).
John Ryan, a biological oceanographer at the Monterey Bay Aquarium Research Institute, said a marine heatwave called The Blob in 2013 altered ocean chemistry and allowed toxic algae to bloom.
He told National Geographic, “It caused the most widespread poisoning of marine mammals ever documented. These were hard times for whales.”
The study also reported that the heatwave triggered a collapse in krill and anchovy numbers, leaving blue whales constantly searching for food.
Ryan added: “When you really break it down, it’s like trying to sing while you’re starving. They were spending all their time just trying to find food.
We don’t hear them singing. They’re spending all their energy searching. There’s just not enough time left over – and that tells us those years are incredibly stressful.”
Blue whales are spending more time foraging than singing (Getty Stock Image).
The Blob is reported to have raised ocean temperatures by more than 4.5°F, causing severe harm to marine life.
Kelly Benoit-Bird, co-author and marine biologist, said, “When we have these really hot years and marine heatwaves, it’s more than just temperature.
The whole system changes, and we don’t get the krill. So the animals that rely only on krill are kind of out of luck.
There are whole ecosystem consequences of these marine heat waves.
If they can’t find food, and they can traverse the entire West Coast of North America, that is a really large-scale consequence.”
As climate change continues to accelerate, scientists warn the oceans could suffer devastating effects, and even small temperature shifts may inflict catastrophic damage on millions.