The Whale Heart That Beats Twice a Minute

Fill your hands with cold water, hold your breath, and press your face in. Your heart slows within seconds. That reflex lives in every whale in the ocean too, and in a blue whale it is pushed so far that the largest heart on Earth can drop to two beats a minute on a deep dive.

In this episode, Andrew walks through the first heart rate recording from a wild blue whale, led by Jeremy Goldbogen's team at Stanford, and a study by Terrie Williams of UC Santa Cruz that tracked narwhals fleeing after release from nets in East Greenland. The narwhals swam as hard as they could while their hearts fell to three or four beats a minute, burning through nearly all their stored oxygen. Andrew also shares what offshore helicopter escape training taught him about holding his breath in cold water.

The episode closes with the good news. Countries around the world already protect whales with distance rules, from 100 yards in the United States to 1,000 metres for endangered Southern Resident orcas in Canada. You will learn the simple steps to take the next time you are on the water with whales, so their dive stays a calm one.

Takeaways

• Every mammal has a dive reflex; in some marine mammals it slows the heart by about 90 percent.
• A tagged blue whale's heart dropped as low as 2 beats a minute on dives and rose to 25 to 37 at the surface.
• Frightened narwhals sprint while their hearts fall to 3 or 4 beats a minute, using 97 percent of their oxygen stores.
• Ship traffic, engine noise, and seismic surveys can trigger this costly escape response.
• Keep at least 100 metres (about 100 yards) from whales, check local rules, and put your engine in neutral if one surfaces close.