Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they have a very slow metabolism, and thu
…s can survive long periods without food. Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks. Many large crocodilians swallow stones (called gastroliths or stomach stones) which may act as ballast to balance their body or assist in crushing food, similar to grit in birds. Salt glands are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles; they seem to be absent in Alligatoridae. Crocodilians can produce sounds during distress and in aggressive displays. They can also hear well and the tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles. Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles. Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may even pant like a dog. It is reported that when the Nile crocodile has lurked a long time underwater to catch prey, and thus has built up a big oxygen debt, when it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomach; the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete very much stomach acid to quickly dissolve bulks of swallowed prey flesh and bone. ( Full Answer )