Gators Divert Blood to Avoid Busting a Gut

Feb. 6, 2008 -- American alligators consume 23 percent of their own body weight in a single meal. To digest such a feast means they must divert gas-rich blood away from their lungs into their stomachs, new research has determined.

The findings, which scientists believe apply to all crocodilians, mean that croc and gator eating can be analogous to a 130-pound woman eating 30 pounds of beef -- bones, teeth and all -- in one sitting.

While young crocodilians will consume a lot of shellfish and fish, adults tend to go for large mammals and whole turtles, which are frequently found in adult alligator stomachs.

"If the prey is not too big to swallow whole, then the entire animal is swallowed," lead author C.G. Farmer told Discovery News. "For bigger prey, several crocs will pull it apart and swallow large pieces."

Farmer, an assistant professor of biology at the University of Utah, and her colleagues may have solved the mystery as to why alligators and crocodiles often find a warm place to quietly recline after consuming a huge meal. On the outside, this behavior looks quite sedate, but inside, extraordinary activity is taking place.

Building upon prior research, the scientists focused on the extra left aorta that crocodilians possess on the side of their otherwise very mammal-like hearts. Normally, blood pumped by the right side of the heart flows through the reptile's pulmonary artery into the lungs, where a transfer of carbon dioxide occurs.

When a croc or gator gorges, however, this blood instead is shunted to the stomach, where the carbon dioxide is converted into gastric acid -- a digestive juice -- and bicarbonate, which functions as a sort of built-in antacid when the time is right.

The gastric acid boost means that crocodilians produce 10 times more digestive juice than the highest rates measured in mammals. If they didn't do this, the enormous quantity of food they eat would putrefy in their guts.

Farmer said, "food can rot in the stomach," but if conditions are warm to support fluid flow in these cold-blooded creatures, digestion can take 10-20 days and mostly eliminate the possibility of rotten food.

The blood shunting offers crocodilians at least two other benefits, according to the researchers, whose findings will be published in the March/April issue of Physiological and Biochemical Zoology .

The first relates to their stealthy hunting tactics.