Hummingbirds have an incredibly fast heart rate, beating up to 1,260 times per minute while at rest. This rapid heart rate is necessary to support their high-energy lifestyle and several physiological adaptations allow hummingbirds to have the highest heart rate of all animals.
What is the average hummingbird heart rate?
The average hummingbird has a heart rate of 500-1,260 beats per minute while at rest. During flight, their heart rates can reach as high as 1,260 beats per minute. The heart rates of different hummingbird species at rest include:
| Ruby-throated Hummingbird | 500 bpm |
| Calliope Hummingbird | 600 bpm |
| Broad-tailed Hummingbird | 1,000 bpm |
| Blue-throated Hummingbird | 1,200 bpm |
The Blue-throated Hummingbird has the highest recorded heart rate of all hummingbirds, reaching up to 1,260 beats per minute. This extremely rapid heartbeat allows hummingbirds to have the energy they need to hover midair and perform their intricate mating dances.
How does hummingbird heart rate compare to other animals?
Hummingbirds have the highest heart rate of all animals. Small mammals such as mice have heart rates around 600 beats per minute while elephants have heart rates as low as 25 beats per minute.
Compared to other birds, hummingbirds far exceed the average bird heart rate of 250-500 beats per minute. Larger birds tend to have lower rates, like ostriches at around 60 bpm. Small songbirds are closer at 400-500 bpm but hummingbirds are in a league of their own.
Why Do Hummingbirds Have Such High Heart Rates?
Hummingbirds have exceptionally high metabolism and energy needs. Their tiny bodies require a lot of energy to support hovering flight, mate competition, and migration. Several key physiological adaptations allow their hearts to beat at such extreme rates.
High Metabolic Rate
Hummingbirds have the highest metabolic rate of all animals relative to their size. Their metabolisms are roughly 10 times faster than an elephant’s metabolism. This ramped-up metabolism allows hummingbirds to generate enough energy to support hovering and other behaviors.
At rest, hummingbirds burn through calories at a rate 10 times faster than reptiles of the same size. During flight, they expend even more energy and can burn through stored food reserves remarkably quickly. Their rapid heart rate delivers oxygen and nutrients needed to fuel this extreme metabolism.
Small Heart Size
Given their tiny size, hummingbirds also have tiny hearts approximately 0.1% the size of a human heart. Their diminutive heart size contributes to the rapid rate. Smaller hearts must beat faster to circulate blood through the body and meet metabolic demands.
Likewise, smaller animals tend to have faster heart rates than larger animals. The shrew, for example, has a heartbeat up to 1,200 beats per minute partly due to its petite body size. Hummingbirds follow the same principle, scaled to an extreme.
Enhanced Capillary Beds
Hummingbirds have a higher ratio of capillaries to muscle fibers compared to other birds and mammals. Capillaries are tiny blood vessels that deliver oxygen and nutrients to tissues. More capillaries mean better diffusion of oxygen into the muscles to support energy generation.
This adaptation allows hummingbird muscles to receive oxygen even during rapid heartbeats. Their capillary beds are so enriched that blood travels only a short distance beyond each capillary before encountering the next one, optimizing oxygen circulation.
Ability to Accumulate Lactic Acid
Hummingbirds have another adaptation that allows their muscles to cope with a frenzied heart rate – an enhanced ability to deal with lactic acid accumulation. Lactic acid is a metabolic byproduct and muscles become fatigued when it builds up faster than it can be removed.
Hummingbirds are able to temporarily accumulate higher levels of lactic acid compared to other animals. This prevents their muscles from becoming overfatigued during periods of extreme exertion when the heart is pumping at maximum speed.
How Do Hummingbirds Survive Their Fast Heart Rates?
Hummingbirds have several remarkable adaptations that allow them to tolerate a heart beating at up to 1,260 times per minute when at rest:
Thickened Ventricular Walls
Hummingbirds have a disproportionately thick left ventricular wall compared to other birds. The left ventricle pumps oxygenated blood to the body and its muscular walls must contract forcefully to handle the physiological demands of hummingbirds.
Thicker, stronger ventricular walls provide more contractile force so blood still circulates effectively even at rapid heart rates. This prevents circulation problems when the heart is beating at top speeds.
Enhanced Cardiac Calcium Cycling
Calcium ions initiate each cardiac muscle contraction and relaxation. Hummingbirds undergo more cardiac calcium cycling that allows their heart cells to contract and relax at accelerated rates by rapidly processing calcium.
Higher densities of calcium channels in heart cell membranes facilitate this efficient calcium movement. This enhanced cardiac calcium processing enables their tiny hearts to beat remarkably fast.
High Stroke Volume
Hummingbird hearts have an exceptionally large stroke volume, which is the amount of blood pumped per beat. Despite their small overall heart size, each beat expels a relatively large amount of blood into circulation.
This compensates for their rapid heart rate and ensures that their tissues still receive adequate blood flow. Even pumping at over 1,000 beats per minute, substantial stroke volume prevents circulation problems.
Advanced Respiratory Control
Hummingbirds have superb control over their breathing and respiration rate. They precisely coordinate heart rate, respiration rate, and wing movement to maximize oxygen circulation while minimizing energy use.
This synchrony ensures their tissues continuously receive sufficient oxygen to support the sky-high metabolic demands of hover-feeding. Their advanced respiratory control prevents oxygen deprivation when the heart is beating at top speed.
Conclusion
In summary, hummingbirds have the fastest heart rate of any animal, beating up to 1,260 times per minute. Their extremely rapid metabolism to power hovering flight and other behaviors necessitates a quick heart rate.
Several cardiovascular adaptations allow hummingbirds to tolerate this extreme heart rate, including thickened ventricular walls, enhanced calcium cycling, substantial stroke volume, and precise respiratory control. So while their tiny size requires a heartbeat faster than other animals, hummingbirds are remarkably equipped to pump blood at these astounding rates.
