Nature never ceases to amaze us with its incredible diversity, and nowhere is this more evident than in the remarkable range of heart rates across the animal kingdom. From the ultra-rapid beats of a hummingbird to the surprisingly slow rhythm of a blue whale's heart, these differences tell a fascinating story about how evolution has shaped animal physiology. Data visualization credit: Visual Capitalist . Data source: Merck Veterinary Manual The Extremes of Nature's Heartbeats Let's start with something extraordinary: while you're reading this sentence, a hummingbird's heart will have beaten about 15 times. According to the Smithsonian's National Zoo , these remarkable creatures maintain a heart rate of up to 225 beats per minute (bpm) even at rest. At the other end of the spectrum, when a blue whale dives deep into the ocean, its heart can slow to just two beats per minute – a rhythm so slow you could count it on one hand. Size Matters: The Science Behind Heart