Alligator is the name of two kinds of reptiles related to crocodiles. The American alligator lives in the waters and lowlands of southeastern United States. The Chinese alligator lives in the lower Yangtze River Valley, in China. Other closely related reptiles are the caymans of Central and South America. Caymans are often called alligators.

Body. Alligators resemble lizards in their shape, but they have thicker bodies and tails than most lizards. Alligators' jaws are set with many sharp teeth. Their eyes stick up above their skulls so that alligators can see above the water while their bodies are beneath it. They use their short, strong legs for walking. Alligators swim by moving their tails from side to side.

An alligator's skin is tough. The skin on the animal's back is rough and ridged with dozens of small bones called osteoderms. The skin on the belly is smooth and was once used to make a handsome, long-lasting leather for handbags, shoes, and other articles. A young American alligator has yellow marks across its body, but these fade after a time. When grown, the American alligator is dull gray and dark olive in color.

Alligators in the past grew to be 18 feet (5.5 meters) long or longer. Today, few can be found that have reached even a length of 12 feet (3.7 meters). Male alligators from 11 to 12 feet (3.4 to 3.7 meters) long weigh from 450 to 550 pounds (204 to 249 kilograms). Females seldom measure more than 9 feet (2.7 meters) long, or weigh over 160 pounds (73 kilograms).

Habits. The female alligator makes her nest of grass and other plants, which she forms into a pile about 3 feet (0.9 meter) high and 7 feet (2.1 meters) across. She lays 20 to 60 eggs in the center of the pile, where the nest is wet. The eggs are white, hard-shelled, and slightly larger than hens' eggs. The young emerge from the eggs after about nine weeks.

Alligators provide more care for their young than do most reptiles. After laying eggs, the female stays near the nest, guarding the eggs against predators. When the young hatch, they give high-pitched yelps, and the mother comes to scratch open the nest and free them. The mother alligator protects her young for a year or more.

When first hatched, the young alligators are about 9 inches (23 centimeters) long. During the first six years of their lives, both males and females grow about 1 foot (30 centimeters) in length each year. After this time, the females grow more slowly. But the males continue to grow at the same rate for several years more. Alligators probably live 50 to 60 years.

In winter, alligators remain resting underwater, bury themselves in mud, or go into deep holes that they have made with their bodies. These holes are called 'gator holes. During droughts, 'gator holes often provide the only refuge for aquatic animals. When rains return, the fish, frogs, turtles, and other animals that have survived in 'gator holes repopulate the swamps and marshy lakes of the South.

Alligators eat many kinds of small animals that live in or near the water, including fish, snakes, frogs, turtles, small mammals, and birds. Large males sometimes attack dogs, pigs, or even cattle. They drag these animals under water to drown them, and then tear them to pieces. Alligators do this by grabbing hold of a part of their prey with their jaws and twisting until that part comes off. Fortunately, even the largest alligators seldom attack human beings. The muscles that close an alligator's jaws are very strong. But once the jaws are shut, they can easily be held closed by a person's bare hands. People have sometimes captured alligators in this way, without using any weapons.

Alligators and crocodiles. Alligators are often mistaken for crocodiles but are different from them in some ways. The fourth tooth of the alligator's lower jaw fits into a pocket of the upper jaw. The same tooth in the crocodile fits into a groove in the side of the upper jaw, making it visible when the animal's mouth is closed. Another way to tell the American alligator from the American crocodile is that the American alligator has a much broader snout. Alligators are also much less aggressive and active than crocodiles. In the United States, alligators and crocodiles are found together only in the marshes at the southern tip of Florida. Both alligators and crocodiles belong to the great group of crocodilians. This group also includes caymans and gavials. See CROCODILE; GAVIAL.

Where alligators live. Alligators were once common in lakes, swamps, and rivers along the Gulf of Mexico and on the Atlantic Coast as far north as North Carolina. They were also found far up the Mississippi River. But so many were killed for their hides or for food and sport that they became scarce. In 1967, the U.S. Fish and Wildlife Service classified the alligator as an endangered species. This designation gave the animal almost complete protection. But by 1977, alligator populations had increased so much in Florida and other southern coastal regions that the animals were reclassified as threatened. This new classification permits tightly regulated hunting of alligators, for commercial purposes.

Scientific Classification. Alligators are in the crocodile family, Crocodylidae. They make up the genus Alligator.

Contributor: D. Bruce Means, Ph.D., President and Executive Director, Coastal Plains Institute.

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Crocodile (reptile, common name for any of a number of reptiles in a family of the crocodilian order. The term refers to all members of the order, which includes as well as crocodiles. Crocodilians first appeared about 200 million years ago and are believed to be remnants of the great age of reptiles. Their ancestors originally lived on land and were lightly built, but they soon diversified into water-dwelling, or aquatic, and amphibious forms. Except for the alligators, crocodilians live in tropical and subtropical areas of the world. Modern crocodilians are amphibious, spending much of their time in water, where they swim with rhythmic strokes of the tail. The tail is sometimes used to capture prey, sweeping it from shallow to deeper water, where it can be devoured more easily. Crocodilians are well-adapted as predators, with few natural enemies. Bony plates, called osteoderms, form a kind of armor in their thick skin. Their teeth, about 30 to 40 in each jaw, are set into sockets in the jawbones and interlock when the mouth is closed. In crocodiles, the fourth tooth on each side of the lower jaw protrudes when the mouth is closed; in alligators, these teeth are not visible. The jaws of crocodilians are powerful enough in closing to crush the bones of small animals, but so weak in opening that they can be held together by hand. As the crocodilian floats almost completely submerged, its protruding nostrils and eyes and a portion of its back are the only parts visible as it stalks its prey. Crocodilians are the most vocal reptiles, producing sounds from quiet hisses to fearsome roars and bellows, usually during the mating season. On land, crocodilians move quickly in a belly crawl but can also gallop and walk mammal-like on all four legs. Crocodiles are physiologically the most advanced reptiles; their internal anatomy resembles that of birds. They have a four-chambered heart and well-developed senses. Cold-blooded like all reptiles '97their body temperature depends on the environment '97crocodilians bury themselves in mud to estivate or hibernate. In warm regions they are dormant during droughts; in colder regions, during winter. Crocodilians are egg-laying, or oviparous, reptiles, reaching reproductive maturity at about the age of ten. The eggs, 20 to 90 in number and about the size of goose eggs, are buried in sand, mud, or vegetable debris, where they are left to hatch by the heat of the sun or of vegetable decomposition. Females of some species remain in the area to protect the nest and care for the newly hatched young, although many of the eggs and young are lost to predators. The parental behavior of crocodilians is unique among reptiles and points to their affinity with birds. The Crocodile Some members of the crocodile family are the largest living reptiles. Crocodiles usually can be recognized by their long triangular snouts, intermediate between the long, narrow snouts of gavials and the short, oval snouts of alligators and caimans. The Indo-Pacific, or saltwater, crocodile, possibly the largest living reptile, is known to grow to a length of about 7 m (about 23 ft) and to weigh more than 1000 kg (more than 2000 lbs); there are unconfirmed reports of individuals up to 9 m (up to 30 ft) in length. This species inhabits the coastal waters of India, southern China, and Malaysia. A smaller species, the swamp crocodile, or mugger, is found in inland waters of India. The Nile crocodile of Africa was revered by certain ancient Egyptian sects, and mummies of crocodiles have been discovered in Egyptian tombs. In modern times this species has been hunted so extensively that few individuals remain in the lower Nile, but they are still abundant in the upper Nile and southward in Africa to the Cape of Good Hope. In the Americas there are four species of crocodiles. The Cuban crocodile, which has a relatively short snout and reaches about 3.5 m (about 11.5 ft) in length, is restricted to Cuba and the Isla de la Juventud. Morelet's crocodile, comparable in size to the Cuban crocodile, occurs along the Gulf Coastal Plain and Yucat\'e1n Peninsula of southern Mexico, Belize, and Northern Guatemala. The Orinoco crocodile inhabits drainages of the Orinoco River system and grows to about 6 m (about 20 ft). The American crocodile, the largest crocodile in the Americas, reaches lengths of about 7 m (about 23 ft) and inhabits a broad range from southern Florida southward, including Cuba and other Caribbean islands, southern Mexico, Central America, and northern South America. Crocodile eggs are used for food in some parts of the world. The skin is highly valued for leather, and the extract from the musk glands is used in the manufacture of perfumes. Due to overhunting, most crocodiles\'97including the American and Nile crocodiles\'97are considered endangered species. Scientific classification: Crocodiles belong to the genera Crocodylus, Osteolamus, and Tomistoma of the family Crocodylidae, order Crocodylia. The Indo-Pacific crocodile is classified as Crocodylus porosus, the swamp crocodile as Crocodylus palustris, the Nile crocodile as Crocodylus niloticus, the Cuban crocodile as Crocodylus rhombifer, the Morelet's crocodile as Crocodylus moreletii, the Orinoco crocodile as Crocodylus intermedius, and the American crocodile as Crocodylus acutus."Crocodile (reptile)," Encarta 98 Encyclopedia. 1993-1997 Microsoft Corporation. All rights reserved.

Crocodile is one of the largest living reptiles. Crocodiles, alligators, gavials, and caymans look much alike, and are all called crocodilians. Both crocodiles and alligators have a long, low, cigar-shaped body, short legs, and long powerful tails with which they swim. They both have tough hides, long snouts, and sharp teeth to grasp their prey. In most crocodiles, however, the snout comes to a point in front, where an alligator's snout is rounded. The American crocodile is only about two-thirds as heavy as an old American alligator of the same length and can move much more quickly. The lower fourth tooth is extra long in both animals. It fits into a pit in the alligator's upper jaw. But the crocodile's fourth tooth fits into a groove in the side of the upper jaw, and it is visible when the animal's jaws are closed.

Crocodiles live in tropical countries throughout the world. They prefer large bodies of shallow water, sluggish rivers, open swamps, and marshes. Their webbed feet allow them to walk on the soft ground. Their eyes and nostrils are higher than the rest of the head. This arrangement fits in with the crocodile's life in the water, for it likes to float with only its eyes and nostrils above the surface. Its throat has a slitlike valve in front of the tube leading to its nostrils. This valve shuts tight when the animal is underwater. It keeps the water from entering through the mouth when the reptile seizes its prey.

Crocodiles eat many small animals, such as fishes, birds, and turtles, which they seize and swallow whole. Occasionally they attack large animals and people. A crocodile can twist a large animal into pieces by seizing it and then rapidly spinning lengthwise in the water. Crocodiles are more aggressive than American or Chinese alligators. Large wild crocodiles should be left alone.

Like most reptiles, crocodiles lay eggs. These look like hens' eggs, but are longer and have a less brittle shell. Crocodiles conceal their eggs in nests of rubbish and vegetation, or they bury them in sand beaches. The female of some types guards the nest until the young are hatched. When she can hear the young reptiles grunting, she digs them out of the nest. Some crocodiles help their young hatch and then carry them in their mouth to the water. Not much is known about the breeding habits and general behavior of crocodiles.

Most of the true crocodiles inhabit the Eastern Hemisphere, but four species live in North and South America. The American crocodile lives in the extreme south of Florida, on the larger West Indian islands, and in Central America and areas near it. The usual length of adult American crocodiles is about 12 feet (3.7 meters).

The Nile crocodile is found widely in Africa. This animal lives almost everywhere on the continent except in the Sahara and on the northern coast. This reptile was known by ancient peoples and described by the Greek historian, Herodotus. The small, long-snouted crocodile of the Congo Basin grows no longer than 8 feet (2.4 meters). The two kinds of dwarf crocodilians of Africa, one of which is very rare, are closely related to true crocodiles.

The giant saltwater crocodile lives in many places from India to northern Australia, and even in the Solomon Islands. The mugger lives in India and Pakistan, and the Siamese crocodile inhabits Java, Thailand, and nearby parts of Asia. There is also an Australian crocodile. Sumatra and the Malay Peninsula have the false gavial. The false gavial has a narrower snout than most other crocodilians. It uses its long snout to catch fish.

The crocodilians are remnants of a large and ancient group of reptiles. Fossils show that these reptiles once reached a length of 50 feet (15 meters). This is more than twice as long as any crocodiles living today. There are now 12 species of crocodiles.

Crocodiles have been widely hunted for their hides, which manufacturers make into leather for shoes and handbags. Such hunting has caused three species--the American crocodile, Cuban crocodile, and Nile crocodile--to become endangered species. Laws now forbid crocodile hunting in many parts of the world, but these restrictions are difficult to enforce. Biologists in some areas have begun programs to collect crocodile eggs and hatch them in incubators. The baby crocodiles are then released into the wild.

Scientific Classification. Crocodiles belong to the family Crocodylidae. The Nile crocodile is Crocodylus niloticus. The American crocodile is C. acutus.

Contributor: D. Bruce Means, Ph.D., President and Executive Director, Coastal Plains Institute.

See also ALLIGATOR; GAVIAL; REPTILE.

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Caiman Cayman, common name for three genera of reptiles in the crocodilian order. They closely resemble alligators except for the small bony scales, or osteoderms, embedded in the skin of their bellies. All are found in the American Tropics. The largest '974.5 m (15 ft) or more in length\'97is the black caiman of the Orinoco and Amazon rivers; it is in danger of extinction, as are many other crocodilians. The smallest caiman, about 1.5 m (about 5 ft), is Cuvier's dwarf or armored caiman, which has heavily ossified, or bony, skin. One of the most abundant and wide-ranging is the spectacled caiman, named for the bony ridge between its eyes, which looks like the nosepiece of a pair of eyeglasses. See Crocodile. Scientific classification: Caimans belong to the family Alligatoridae in the order Crocodylia. The black caiman is classified as Melanosuchus niger, the armored caiman as Paleosuchus palpebrosus, and the spectacled caiman as Caiman crocodilus crocodilus."Caiman," Microsoft Encarta 98 Encyclopedia. 1993-1997 Microsoft Corporation. All rights reserved.