
The largest animal to ever live on Earth is going quiet and scientists have issued a terrifying warning.
At 100 feet long, which is about the length of three school buses, there are said to be between 10,000 and 25,000 blue whales alive in the ocean today.
With a tongue weighing the same as an elephant and a heart the size of a small car, blue whales are becoming increasingly silent.
Their low-frequency calls travel hundreds of miles underwater and scientists have relied on those vocalisations for decades to track populations and behaviour.
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Blue whales communicate in this way to help find mates, coordinate movement and maintain social bonds.
But in some regions, researchers are reporting fewer calls.

Why blue whales are going silent
Back in 2015, researchers tracked whale noises for six years during a massive marine heatwave known as 'The Blob'.
During this heatwave, ocean temperatures spiked, disrupting the food chain and causing a dramatic drop in krill, their primary source of food.
The average blue whale eats up to four tons of the tiny shrimp-like creatures a day, perhaps explaining why they weigh around 200 tons.
Scientists believe the sudden drop in blue whale noise is a red flag for ocean health, with the silence signalling deeper environmental issues.
"When you really break it down, it’s like trying to sing while you're starving," John Ryan, a biological oceanographer at the Monterey Bay Aquarium Research Institute, told National Geographic.
"They were spending all their time just trying to find food."

What happens if blue whales go extinct?
Global warming means more heatwaves and more of a chance of whales going silent.
“There are whole ecosystem consequences of these marine heat waves,” oceanographer Kelly Benoit-Bird warned.
“If they can't find food, and they can traverse the entire West Coast of North America, that is a really large-scale consequence.”
The Animal Welfare Institute added: "Whale fecal plumes contain valuable nutrients like iron, nitrogen, and phosphorus.
"They stimulate production of microscopic marine algae, or phytoplankton, which form the base of many aquatic food chains.
"Whales also transport nutrients in their fecal plumes, urine, sloughed skin, and placental materials horizontally, a phenomenon referred to as the 'whale conveyor belt', as they migrate between nutrient-rich feeding areas and nutrient-limited breeding/birthing areas."
Without blue whales, many marine ecosystems and the species that depend on them would be at risk.
Topics: Animals, Environment, Ocean