A blue whale’s heart can fall to two beats a minute
A tagged blue whale, diving off California, had a heart rate of four to eight beats a minute at depth, and at moments two. At the surface the same heart reached the high thirties.
In 2019 a suction-cup tag with electrodes rode a blue whale through dives as deep as 184 metres and as long as sixteen minutes. On the way down the rate collapsed. At the bottom it sat around four to eight beats a minute, and it touched two. During a lunge through krill it rose, still in single digits. Back at the surface it climbed to between 25 and 37, close to the fastest that heart is thought able to beat.
A pause that long would empty a human pulse. The whale’s aortic arch is wide and elastic, so one contraction loads the vessel and the vessel then pays the blood out slowly until the next beat. The measurement is one animal, one set of dives. It is the first time the rate was taken on a free-diving blue whale, which is why the number is allowed to be this strange, and why it is not yet a census.
Caveats
- Two beats a minute is the floor they recorded, not the rate at the surface and not a permanent state. Most of a deep dive sat higher.
- One whale. The design of the aorta is known from other rorquals. The electrocardiogram is this animal’s.
Sources
- 1Goldbogen J. A. et al.. Extreme bradycardia and tachycardia in the world’s largest animal. Proceedings of the National Academy of Sciences 116, 2019.