 A blue whale surfaces to breathe just before a researcher affixes a heart rate recording tag. (M.S. Savoca) | | | Blue whales exist at the limits of biology. They are the largest animals ever to have lived, and their hearts reflect this superlative bulk. Take it away, National Oceanic and Atmospheric Administration: A blue whale heart is so big, a person could shimmy through its valves. It's so big that it weighs 1,000 pounds, as much as a cow. It's so big that a single heartbeat sends about 60 gallons of blood coursing through its veins. For the first time, scientists have affixed a heart rate monitor to a wild blue whale, as they reported in a study published this week in the journal Proceedings of the National Academy of Sciences. The procedure was noninvasive — researchers stuck surface electrodes to the whale's skin — but nonetheless tricky to pull off. "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 Stanford University biologist and study author Jeremy Goldbogen, in a news release. The scientists successfully traced the heart rate of the whale as it dove. At rest, the whale's heart rate was 15 beats per minute. It dropped to 2 bpm when diving. And as it surfaced and lunged after food, the beats jumped to around 40 bpm, the fastest a heart of this mass could go. The data paint a picture of an enormous organ operating at extremes, suggesting the limitations of their hearts prevent whales from growing any larger. Humans can be thankful for each drumlike beat. Living blue whales are worth tons of cash, economists recently calculated, because they store so much carbon on their bodies. |
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