How Long Can Alligators Stay Underwater and Hold Their Breath?

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American alligators (Alligator mississippiensis) spend their lives in a “half & half” cycle—that is, they live both in the water and on land, although it may be more like 90-10. They are neither fish nor mammal. As semiaquatic reptiles, alligators inhabit environments that simultaneously appear natural and unnatural to their physiology.

Swamps, rivers, marshes, lakes, ponds, and other freshwater bodies provide the aquatic backdrop for the majority of the lives of this prehistoric-looking species. Little, however, about the alligator is primitive. While alligators spend the overwhelming majority of their lives in the water, they cannot breathe underwater, a trait they share with the mammals of the ocean such as whales, seals, sea lions and otters, and dolphins. Their morphology beautifully and perfectly aligns with this reality. No gills, no problem.

As for their lives on land, these crocodilians leave the water for several reasons. First, as cold-blooded, or ectothermic, creatures, alligators cannot internally regulate their body temperature. They do this primarily by basking in the sun’s warmth or seeking warm surface water. Second, like birds, alligators lay eggs. Nesting necessitates that females leave the water. In mid-spring, April and May, alligators mate. By June or July, female alligators (sows) are constructing nests in isolated locations for their clutch by gathering vegetation into a mound. Third, alligators hunt on land, and their carnivorous diet includes more than just fish and turtles. Additionally, their physiology does not prevent them from moving on land. They move well on land, running in bursts at speeds of 10 to 20 miles per hour. Lastly, alligators sometimes move from one body of water to another. Therefore, they occasionally travel on land.

Take a Breath

Alligators must resurface for air just like marine mammals. This means that they must hold their breath underwater. The time they can remain submerged varies according to the source, but it is safe to say that an alligator in ideal weather conditions (i.e., warm but not too warm, between 82° to 92° F when they are most active) will emerge from the watery depths every 15 to 45 minutes to breathe.

Interestingly, alligators are not capped at that range of time. Their physiology allows alligators to far exceed that length. A 1962 news release from the University of California, San Diego, summarized research by Dr. Harald T. Andersen, then a physiologist at the University of Oslo, Norway: “Dr. Andersen found evidence that certain circulatory adjustments in the submerged alligator shut off the blood
supply to some organs and tissues not critically dependent upon a continuous supply of oxygen.” It is widely accepted that alligators can hold their breath for up to two hours, although some argue they can hold their breath for up to 24 hours; however, this would not be typical behavior.

The Heart of the Matter

Crocodilians share several attributes with mammals and birds. Most notably, their hearts have four chambers. Oxygenated and deoxygenated blood are separated in a four-chambered heart, whereas some of the former is mixed with the latter in the three-chambered heart that is characteristic of all reptiles but crocodilians.

Additionally, all reptiles have two aortas; mammals (including humans) and birds have one. Only one reptile order has a foramen of Panizza, described as a hole with a valve between the left and right aortas and named for Italian anatomist Bartolomeo Panizza who first described it in 1833.

This hybrid cardiac system may seem like overkill for the ectothermic alligator.

The alligator heart’s morphology is just perfect, though. A four-chambered heart allows for more efficient respiration and enables different pulmonary (lung) and systemic blood pressures, according to the American alligator fact sheet for the Florida Fish and Wildlife Conservation Commission. When the foramen of Panizza opens, oxygenated blood from the right ventricle bypasses the lungs, which “helps crocodilians transition to a lower metabolic state and enables them to dive for extended periods.”

In other words, alligators can ration their oxygen when submerged because, as Zoo Atlanta explains it, “blood does NOT have to unnecessarily flow to the lungs when the crocodilian is underwater.”

When alligators are submerged for long periods, their heart rate slows dramatically, a state known as bradycardia. It is believed that alligators and their relatives can slow their heart to just 2-3 beats per minute and that “the heart may be the alligator’s only oxygen-receiving muscle during submersion,” noted the UCSD news release.

A Little (Lung) Goes a Long Way

Alligators are ambush hunters, meaning they often lie in wait, patiently and slowly moving toward their prey. The internet boasts countless videos showing how imperceptible these giants of the swamp can be. The water will appear completely still, yet underneath or at its surface lies an enormous reptile. Without warning, the alligator emerges with such speed and force to snatch up its latest meal, leaving witnesses wondering how the alligator was able to approach without generating so much as a single ripple in the water.

To answer this, researchers T. J. Uriona and C. G. Farmer from the University of Utah set out to test whether the alligator’s various muscles known to play a role in respiration were also recruited for aquatic locomotion. In short, lungs serve purposes beyond just breathing, according to their research, which was published in the Journal of Experimental Biology.

Like humans, alligators use their lungs for flotation. However, research by Uriona & Farmer shows that alligators use four sets of muscles—M. diaphragmaticus, M. ischiopubis, M. rectus abdominis, and M. intercostalis internus—to shift their lungs within their torso. By expanding and contracting these muscles, alligators can move up and down (rise), forward and backward (dive), and side to side (roll) with minimal water disturbance, which enables them to easily blend into their surroundings and covertly approach prey.

“The hips, muscles[,] and liver all act like a massive piston that shunts the lungs back and forth across the alligator’s chest, moving its centre of buoyancy with them,” writes Ed Wong for National Geographic in an article about Uriona & Farmer’s research.

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