Crocodiles are reptiles with a more ferocious look as they have larger teeth, a greater number of which protrudes when the mouth is closed. Though it has very large teeth, it can neither move its tongue nor chew the food it eats. It also cannot stick out its tongue. A membrane helps to hold its tongue in place. This carnivore which never feeds on plants secretes very strong digestive juices which are capable of even digesting a steel nail.
At zoos, you may find that the crocodiles are fed not more than once a week. As they cannot chew, they rip off large pieces of their prey and swallow the chunks as a whole. Swallowing as such results in a slow digestive metabolism. This is the reason why they can survive a long time without food.
There are about 13 different species of crocodiles that live in salt water or fresh water. The tongue of certain species have got salt glands which helps to secrete the excess salts from their body. Such species can tolerate life in salt water while others prefer to live in fresh water. Humans are the greatest threat to crocodile family. Eight species of crocodiles are known to have attacked humans.
Crocodiles are estimated to have appeared around 250 million years ago. They are the closest relatives of birds. They are excellent swimmers and can walk through land too.