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Why Blue Whales’ Hearts Are Stopping Their Bodies From Getting Bigger

A photo of a blue whale is pictured in this image from September, 2010.

Photo by National Oceanic and Atmospheric Administration

Above: A photo of a blue whale is pictured in this image from September, 2010.

Researchers across California, including some at UC San Diego, are looking at the heart of the Earth's largest species — the blue whale. The researchers captured the first-ever heart beat recording from the giant marine animal.

Scientists at the Scripps Institution of Oceanography and Stanford University spotted some blue whales in Monterey Bay.

David Cade, a scientist with Stanford, said studying blue whales could help scientists understand the limitations of life on earth.

"Blue whales are one of the answers to the limits of life, like how big can something be? Look at the blue whale, how does it function? How does it get to be as big as it does? One of the big unknowns is about the whale’s metabolism, energetic use and heart rate," Cade said.

When the whales were spotted, scientists carefully attached sensors to their flippers using suction cups. Cade said the bigger the heart the longer it will take to contract. That means blood pumps through the body at a slower rate.

"As the animal keeps getting bigger, its heart has to keep increasing in size, which means that the time it takes for the heart to contract keeps getting bigger and bigger. Yet, it can’t increase its heart rate to resupply the oxygen it’s used up," Cade said.

What they found is that when the blue whale reaches the surface of the ocean, its heart is working at its highest physical capacity so it can recover enough oxygen.

"A whale’s heart beat is so big it takes about 2 seconds for that heart to contract. At the surface we found that heart rate to be about 40 beats per minute. Meaning that this whale in its normal routine has its heart pumping about as fast as physically possible," Cade said.

Cade said the discovery may point to why no other animal on earth has been able to outsize the blue whale. Because a larger heart may not be able to keep a bigger animal alive.

Listen to this story by Shalina Chatlani.

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Photo of Shalina Chatlani

Shalina Chatlani
Science and Technology Reporter

opening quote marksclosing quote marksI cover all things science and technology — from the biotech industry in San Diego to rooftop solar energy on new homes. I'm interested in covering the human side of science and technology, like barriers to entry for people of color or gender equity issues on biotech boards.

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