The heart of a blue whale weighs about a half a ton, 1000 lbs. It has to be large enough to pump about 15,000 pints of blood as compared to about 8 pints in a human.

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The average heart rate for a man is 72bpm. A blue whale’s heart beats six times a minute. A horse has 38bpm. A rabbit has 205bpm. A rat 420. A mouse 670. The heartbeat of a canary occurs 17 times in a second. 

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A rate of 1260 beats per minute was measured in a Blue-throated Hummingbird. In torpid hummingbirds, the heart rate can drop to 50-180 per minute. 

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A giraffe depends on it’s powerful heart that weighs up to 12kg so that it can fight the force of gravity up that long neck to the head. 

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Zebrafish can regenerate its heart.