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.
Since the large reptiles leap onto their prey, drag it and drown it in short order, an enormous amount of lactic acid releases from their muscles. This acid contributes to feeling tired after exercise in humans.
Crocodilians clear the potentially lethally large doses of acid from their bodies in the blood that shoots to their stomachs.
The process may also benefit young crocs, which have to jockey for sunny space by squeezing themselves around older, more dominant, lounging adults. Since they too can send gas-rich blood into their stomachs, it helps that the blood movement can occur quickly, before they lose their sunspot.
James Hicks, a University of California at Irvine professor of ecology and evolutionary biology whose lab is currently studying crocodilian circulation, told Discovery News that researchers have debated about why croc blood can bypass lungs for a while.
He said the two most common theories are that the process contributes "to the croc's capacity for extended, underwater dives" and that, per the recent study, it helps with digestion.
"Dr. Farmer's paper provides the first experimental test and supporting evidence for one of these hypotheses," he said.
Impressive as crocodilian digestion is, there is something that the animals just can't stomach.
"They can't digest hair," Farmer said. "The hair of their prey forms small pellets, and these are regurgitated."
Related Links:
Jennifer Viegas' blog: Born Animal
our sites
video
mobile
shop
stay connected
corporate
