Crocodiles can hold their breath for more than an hour. The average is 15 minutes, and some even speculate that they can hold it for eight hours, but only if they are sitting still. Under normal conditions, they can go as far as two hours if not stressed.
The eight-hour assumption is based merely on calculations. Crocodiles have the ability to redistribute oxygen to the rest of the body at will.
The theory is that they can last for eight hours underwater if they are not doing anything at all, as this will not take much energy and oxygen to do.
How Long can Crocodiles Stay Underwater?
The consensus among zoologists is that crocodiles generally stay underwater for between 10 and 15 minutes, although in specific circumstances they may be able to hold their breath for up to two hours.
This length of time, 10 to 15 minutes, is only applicable if the crocodile is on a voluntary dive. Scientists say that if the crocodile feels under threat, it can stay underwater longer than this.
If pressed further, like if it is hunted, the crocodile can stay underwater for two hours, making it extremely dangerous to animals near water.
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How Do Crocodiles Hold Their Breath for So Long?
Crocodiles can hold their breath for long periods by reducing their movement and lowering their heart rate to only a few beats per minute. This conserves oxygen and allows them to hold their breath for long periods.
Crocodiles, like humans, have a heart that has four chambers. The heart pumps blood to the veins, and the veins take the blood to different parts of the body.
Crocodiles can conserve energy by lowering their heart rate, and thus reducing the amount of oxygen required.
Crocodiles have the ability to move physically without using a lot of oxygen. This process is called anaerobic respiration. The cells do not have to breathe to be able to move. The energy that they use comes from glycolysis, a process which breaks down sugars to get energy.
Related Article: What Do Saltwater Crocodiles Eat?
Do Crocodiles Sleep Underwater?
Crocodiles can not sleep underwater. Unlike fish or amphibians that can extract oxygen from water, crocodiles have lungs and need air to breathe.
Crocodiles sleep several times every day, but not for long periods. Most of the time, they sleep at night. However, some crocodiles are nocturnal, so they find a balance between hunting and sleeping.
As light sleepers, they do not enter REM or rapid eye movement sleep. Crocodiles wake up at the least disturbance. It is why many people will never catch a crocodile sleeping. They evolved like this because it is necessary for survival.
A study shows that crocodiles can sleep with one eye open. In the study, the crocodiles kept their open eye on the human experimenter while the other eye was closed. The study was recorded with infrared cameras.
The scientists concluded that crocodiles go through uni-hemispheric sleep—something that aquatic animals can also do. It also indicates that the crocodiles may sleep with half a brain functioning. Uni-hemispheric sleep is slow-wave sleep. Half of the brain rests, while the other half stays alert.
Related Article: Can Crocodiles and Alligators Live Together?
Does Crocodile Breathe Through Gills?
Crocodiles do not have gills. They have a similar respiratory system to humans. The air goes in the nostrils; then it travels through the windpipe.
However, the similarity ends there. Studies indicate that crocodiles breathe like birds. In humans, the breathing pattern is tidal. It is like the tides in the sea that goes back and forth. The air goes out the same way it entered.
Crocodiles and birds do not breathe this way. Instead, their breathing pattern is unidirectional. The air goes through many loops in various parts of their bodies. Despite this ability, crocodiles can drown. They must breathe air in the same way many land animals do.
Read More: Why Crocodiles Aren’t Considered Marine Mammals
Do Crocodiles Breathe Through Their Skin?
No, crocodiles cannot breathe through their skin because they are reptiles. Only amphibians that can breathe through their skin.
Most amphibians can breathe through their skin, but not all. The skin absorbs oxygen from the water. Amphibians do not breath air from the skin. The oxygen that they absorb through the skin will go to their blood vessels.
As reptiles, crocodiles have scales. These scales, particularly for the crocodile and alligators, are called scutes. They are thick and bony, and air cannot penetrate them. Crocodiles breathe through the lungs.
Despite the scutes being thick, they do have sensitive nerve endings. They are sensitive enough to feel the touch of a fingertip.
Read More: Are Crocodiles Lizards?
Summary
Crocodiles can hold their breath underwater for 15 minutes. They have the ability to reduce their heartbeat and also conserve energy. When they do this, they can use another energy source to attack prey while they are lurking underwater.
Crocodiles are not fish. They will drown if they stay underwater too long. Like land animals, crocodiles must breathe air. They are also not like amphibians—they cannot breathe through their skin.
Stuart is the editor of Fauna Facts. He edits our writers’ work as well as contributing his own content. Stuart is passionate about sustainable farming and animal welfare and has written extensively on cows and geese for the site.