Animal Behaviour

Hunting Mechanism

How do they hunt then? Despite their appearance of being slow, crocodiles have a very fast strike and are top predators in their environment, and various species have been observed attacking and killing other predators such as sharks and big cats. As opportunistic predators, crocodiles would also prey upon young and dying elephants and hippos when given the chance. Crocodiles are also known to be aggressive scavengers who feed upon carrion and steal from other predators. There's been evidences that suggest that crocodiles also feed upon fruits, based on the discovery of seeds in stools and stomachs from many subjects as well as accounts of them feeding.

Digestion System

Crocodiles have the most acidic stomach of any vertebrate. They can easily digest bones, hooves and horns. The BBC TV reported that a Nile crocodile that has lurked a long time underwater to catch prey builds up a large 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 more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone. Many large crocodilians swallow stones (called gastroliths or stomach stones), which may act as ballast to balance their bodies or assist in crushing food, similar to grit ingested by birds. 

Bite

Since they feed by grabbing and holding onto their prey, they have evolved sharp teeth for piercing and holding onto flesh, and powerful muscles to close the jaws and hold them shut. The teeth are not well-suited to tearing flesh off of large prey items as is the dentition and claws of many mammalian carnivores, the hooked bills and talons of raptorial birds, or the serrated teeth of sharks. However, this is an advantage rather than a disadvantage to the crocodile since the properties of the teeth allow it to hold onto prey with the least possibility of the prey animal to escape. Otherwise combined with the exceptionally high bite force, the flesh would easily cut through; thus creating an escape opportunity for the prey item. The jaws can bite down with immense force, by far the strongest bite of any animal.

Defense Mechanism

Crocodiles can use their tails for protection, but their main form of defence is to bite attackers with their powerful jaws, equipped with sharp teeth to penetrate and hold on. Research indicates that crocodiles have a bite comparable to the low end of the power that T Rex was estimated to have. 

As crocodiles are apex predators, at the top of their food chain, they have minimal need to protect themselves from other predators.

Sleeping

Crocodiles (and other reptiles) do "sleep," but not quite in the way we do. Human sleep can be divided into two main types, REM (rapid-eye-movement) and non-REM sleep (non-REM includes SWS or short-wave sleep). Some reptiles show signs of REM, but crocodiles apparently don't. Non-REM sleep is generated by the cerebrum in mammals, but reptiles have very little cerebrum; the electrical signs of non-REM sleep in reptiles occur below the cerebrum in the basal ganglia. Also, since reptiles are poikilothermic ("cold-blooded"), they are unable to regulate their temperature while asleep. Interestingly, since the fundamental functions of sleep evolved with homeothermy ("warm-bloodedness"), it follows that reptiles should be able to do without sleep. 

As for a sleep pattern, crocodiles probably "sleep" in short bouts, night or day, between periods of activity, especially after eating. Digestion is facilitated during sleep by shutting down other body functions.