MargenA blue whale's heart weighs around 180 kilos: like an upright piano. It's the largest that has ever existed in any animal.
In 2019, a Stanford team pulled off what seemed impossible: attaching a suction-cup electrocardiograph to a blue whale in the open sea. The recording left the scientists stunned. When the whale dives to feed, its heart drops to two beats a minute; back at the surface, it races to more than thirty to reload on oxygen.
Thirty seconds can pass between one beat and the next. A thirty-metre animal running on the pulse of someone in the deepest sleep.
The researchers believe that heart is already working at the limit of what is physically possible — one of the reasons no animal has ever been any larger.
Source: PNAS · Universidad de Stanford