Wednesday, January 27, 2010

Crocodile

Crocodiles are large amphibious reptiles related to Alligators, Caimans, and Gavials. They are distinguished by a notch at the side of the snout that exposes the elongate fourth tooth of the lower jaw, thus fiving a crocodile’s face its typical expression. Crocodiles are found in tropical Africa, Australia, and Asia. In the islands of the western Pacific Ocean; and in the tropical parts of North of South America.







The smallest species is the broad fronted, or dwarf crocodile, Osteolaemus tetraspis, of West Africa, which seldom exceeds lengths of 1.5 m (5 ft), the largest is probably the saltwater crocodile, Crocodylus porosus, of southeastern Asia, with a length of up to 6 m (20 ft), although some reports give up to 9 m (30 ft). Several species, including the American and the Nile crocodiles are known to have also reached length of up to 6 m (20 ft) and to weight a ton or more.

Crocodiles swim or float the surface of the water, exposing only their eyes, nostrils, flat tail, and webbed toes. A fleshy value in the throat allows them to open their mouths in the water without choking. The nostrils and ears can also be closed to keep out water. Besides the normal upper and lower eyelids, crocodiles have a transparent third eyelid, the nictitating membrane, which allows them to see underwater. Crocodiles swim by moving their tails.

Most crocodile hunt at night and bask during the day, hungry crocodiles hunt during the day as well. Generally, they feed on other vertebrate animals. Crocodiles vary among species in the prey they prefer. Some broad fronted crocodiles typically feed on frogs, birds and small mammals, whereas specialized narrow snouted crocodiles feed primarily of fish. Such large species as the saltwater crocodile and the Nile crocodile often catch large animals for example, antelopes, deer, and hogs, and are known to attack humans.

The female crocodile lays her eggs in nest made of vegetation or in sand banks and remains with them until the heat of the Sun causes them to hatch about three moths later. It is believed that she digs up the young when they begin to call and either carries them in her mouth or leads them to the water.

Crocodile originated during the late Triassic Period, 200 million years ago. During the Cretaceous Period, about 120 million years ago, crocodiles existed that were so large – 12 m (40 ft) or more – they may have preyed on dinosaurs.

Crocodiles belong to the family Crocodylidae, order Crocodylia. The 11 species that exist today belong to three genera. Tomistoma, the false gavial of the Malaya Peninsula, Sumatra, and western Borneo; Osteolaemus, the broad fronted crocodile of West Africa, and Crocodylus (nine species), the true crocodile. Several species of crocodile, including the American crocodile, C. acutus, are in danger of extinction, their existence threatened by habitat loss and hide hunters.

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