The crocodile is a lizard-like, flesh-eating reptile. It is the largest and heaviest of all present-day reptiles. It is related to the alligator.

Where crocodiles live

Crocodiles live in swamps, lakes, and rivers in tropical and sub-tropical regions. They are found in Africa, Madagascar, India, Sri Lanka, southeast Asia, northern Australia, Mexico, the West Indies, and the Americas. The American crocodile is the only species that lives outside the tropics.

Physical features

Crocodiles have many interesting physical features that are useful for living in the water and catching their prey. Crocodiles have long snouts that vary in proportion and shape. They have a tough skin covered with large horny plates called scutes. Thick bony plates cover their back.

Because their eyes and nostrils are on top of their head, crocodiles can see and breathe even when their body is submerged in water. This helps them surprise and catch larger prey.

In addition, crocodiles have external ears that close when they dive in water. The third eyelid, or the nictitating membrane, is another feature that helps them to live in water. This clear membrane closes while the eyelids remain open, allowing the crocodile to see under water.

Crocodiles also have short and powerful legs. Their front legs have five toes, and their hind legs have four wholly or partially webbed toes.

Although crocodiles look like alligators, it is easy to tell them apart. The fourth tooth in the lower jaw of crocodiles always sticks out, whereas in alligators it fits into a socket in the upper jaw.

There are about a dozen known species of crocodiles, all of which vary greatly in size. The dwarf crocodile of the West African rain forests measures only 6 feet (1.8 meters) in length. The giant estuarine crocodile of tropical Asia and Australia, on the other hand, may grow to almost 30 feet (9 meters). This type of crocodile is the largest living reptile in the world.

Behavior

Young crocodiles feed on insects, frogs, and small fish. Adult crocodiles feed on larger fishes, turtles, and birds. Crocodiles capture water animals in their jaws with a sideways movement of the muzzle. To capture land animals, they wait motionless at waterhole edges. In a surprise attack, crocodiles seize their prey by the feet and drag it quickly toward the water. Sometimes they knock the prey off balance with their tails. When they cannot consume the whole prey, they store it in their burrows. Some crocodiles, such as the Nile crocodile and the estuarine crocodile, have been known to attack humans.

Among all reptiles, crocodiles have the most highly developed brains. They are very curious and can be tamed. If kept captive from birth, some crocodiles learn to recognize their keepers. In captivity, they do not show fear or aggression, they beg for food, and they accept being petted. In other words, they change their behavior to adapt to the environment of captivity.

Life cycle

Crocodiles reproduce by laying hard-shelled eggs. Some crocodiles can lay more than 100 eggs. The female builds nests of mud and dead leaves as shelter for the eggs. As the plants rot, they give off enough warmth to help the eggs hatch. The female remains close to the nest and protects the eggs from predators until the eggs hatch. While still in the egg, the baby crocodiles utter squeaking sounds, perhaps indicating that they are ready to be born. The female then removes the dirt or other debris from the eggs. After that, she does not provide any more care for them; they are on their own. In most species, the young move by instinct toward the water. However, the female Nile crocodile carries the hatchlings to the water in her mouth.

Newborn crocodiles are about 8–10 inches (20–25 centimeters) long. They remain hidden at the water's edge to escape predators, which include fish, birds, and larger crocodiles. During the first three to four years, the young increase in length by about 1 foot (about 30 centimeters) per year. The growth rate then gradually decreases, but growth can continue throughout life.

Environmental issues

The American crocodile and the mugger, or marsh crocodile, are endangered species. Their habitat changed because of city development, making it difficult to live. Also, they were killed for their skins.