Chomp on This! Why Crocodiles are a Cardiac Marvel

American crocodile, Crocodylus acutus

Intended to raise awareness about the leading cause of death in the United States—cardiovascular disease—February is American Heart Month. While we all understand the importance of diet and exercise in maintaining and lowering blood pressure and LDL cholesterol for heart health, few realize that one group of vertebrates has an actively controlled, neuroregulated heart valve—crocodilians. Yep. Alligators and crocodiles have a special valve in their hearts called a “cog-tooth valve,” which allows them to consciously control the flow of their blood. Wow!

Unlike other reptiles, crocodilians have a four-chambered heart that separates oxygenated from deoxygenated blood, just like ours. This feature actually makes them more closely related to birds on the evolutionary tree than to lizards.

Located at the base of the aorta, this cog-tooth valve, a cardiac shunt, can be controlled at will to redirect blood flow. During a deep dive, crocodilians can shunt this valve and send all their oxygenated blood directly back into the bloodstream, bypassing the lungs for reoxygenation—reducing the need to breathe. Tadda. This allows them to stay submerged for a documented seven to eight hours. How long can you hold your breath?