It's a rule of nature that the typical heart rate of an animal increases as the size of the creature decreases.
For instance, a hummingbird's heart beats more than 1,200 times per minute during flight, whereas your heart is probably pumping out blood at a rate of between 60 and 100 beats per minute.
With that in mind, would you care to guess how many times the heart of a blue whale -- the largest animal that has ever existed on Earth -- beats every minute? Of course, it depends on how much activity is going on, but at the low end of the scale, a blue whale's heart can slow to just two beats every 60 seconds.
Scientists measured the massive cetacean's heartbeat with an electrocardiogram machine wired to the whale via suction cups. On the surface, the machine showed the whale's heart beating at a top speed of 37 beats per minute, but when it dived deep below the surface -- blue whales commonly look for food at depths of 500 feet (152 m) -- its heart rate decreased to just two beats per minute.
The findings were based on nine hours of data collected from a male blue whale off the coast of California in 2019. The whale was of average size for an adult, reaching a length of 72 feet (22 m). The successful endeavor was the first of its kind because of the effort required.
"First we have to find a blue whale, which can be very difficult because these animals range across vast swaths of the open ocean," said Jeremy Goldbogen, a Stanford University marine biologist who led the study. Goldbogen said it was then a combination of skill, luck, and timing to get everything to work.
Big and blue all over:
- Despite its unprecedented size, the blue whale survives on some of the smallest creatures in the ocean: Tiny, shrimp-like animals known as krill.
- Although few predators take on blue whales, the marine behemoths are sometimes killed in collisions with ships.
- A blue whale's heart is the size of a car, and its tongue weighs as much an elephant.