Whale Heart Rates Change With Size and Diving

Large mammals generally have slower heart rates than small ones: heart rate declines as body mass increases. A blue whale’s rate also changes sharply with diving; researchers recorded as few as two beats per minute during deep dives, while it rose after surfacing. The estimate of about nine beats per minute comes from a separate measurement of a non-diving humpback whale and is not a fixed rate for all whales. The illustration is AI-generated.