Crocodiles have no lips and can hold their breath for an hour.
Crocodiles can hold their breath underwater for more than an hour.
Crocodiles have a unique breathing pattern that allows them to hold their breath for extended periods while diving. When a crocodile submerges, it shuts its nostrils and closes the flap of skin that covers its throat, preventing water from entering its respiratory system.
Researchers in Cambridge have now shown that this ability depends on a tiny fragment of the animal’s haemoglobin the protein that carries oxygen from the lungs to the rest of the body.
Crocodiles use a waste product of metabolism – the bicarbonate ions formed when carbon dioxide dissolves in water – as the trigger for haemoglobin to unload the oxygen it carries. The more energy the crocodile’s cells burn up, the more carbon dioxide they produce. So the bicarbonate triggering mechanism ensures that large quantities of oxygen are supplied only to the hard-working tissues that need it the most, thus conserving a submerged crocodile’s limited supplies. This efficient system of oxygen allocation, combined with the reptile’s very slow metabolism, explains how it is able to survive underwater for so long.