The new research notes that another important factor allowing blue whales to grow so large is their highly specialized cardiovascular system. For marine biologists, however, understanding exactly what makes the blue whale’s heart tick has proven difficult given they’re almost too big to measure. To overcome this hurdle, Goldbogen and his colleagues developed an electrocardiogram (ECG) tag that they attached to a blue whale with suction cups.
That’s right—suction cups.
“I honestly thought it was a long shot because we had to get so many things right: finding a blue whale, getting the tag in just the right location on the whale, good contact with the whale’s skin and, of course, making sure the tag is working and recording data,” said Goldbogen in a press release.
The researchers managed to attach their device next to the flipper of a 15-year-old male blue whale in Monterey Bay, California. The device tracked the rhythms of the whale’s heart as it dove to depths of 184 meters (604 feet), and as it stayed underwater for nearly 17 minutes at a time.
Looking at the results, the researchers were able to chronicle the blue whale’s heart rate as it went about its daily routine. When the whale made a deep dive, its heart rate slowed to a crawl, beating around 4 to 8 beats per minute (bpm) on average, and sometimes as slow as two beats per minute (the normal resting heart rates for humans is between 60 to 100 bpm). With this radically diminished heart rate, the whale was able to conserve its blood oxygen supply, allowing it to stay underwater for prolonged periods of time and maximize foraging time.