Forest Preserve District of Cook County, Illinois
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Alligators and Crocodiles
Nature Bulletin No. 519-A    March 2, 1974
Forest Preserve District of Cook County 
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

The crocodilians, which include alligators, caimans, crocodiles and the gavial, are living fossils -- swamp dwelling survivors from the Age of Reptiles when dinosaurs ruled the earth. Almost every tropical country has one or more kinds of them and in Columbia, South America, there are seven or eight. Only the two species of alligators live in more temperate regions: one in the United States and the other, almost extinct, in the Yangtze valley of China.

The American Alligator is now common only in the watery interior of Florida, the great Okefenokee Swamp and the Louisiana bayous. The American Crocodile, of which a few remain in Everglades National Park and the Florida Keys, ranges through the West Indies and from southern Mexico to Ecuador. The most obvious difference between them is that an alligator's snout is much broader. The crocodile is far more vicious.

The body of a crocodilian merges imperceptibly into its massive tail which serves to propel the animal in water and also as a weapon. With a swift sideswipe of that tail, a big "croc" can knock a man down and break his leg. On land, except when sliding into water, the body is carried considerably above the ground by its four thick legs -- sometimes at amazing speed. The back is protected by a tough armor of horny scales reinforced by plates of bone.

A crocodilian gets most of its food in water and takes to water for protection, but loves to bask on sunny banks and the females must have land on which to lay their eggs. Its nostrils are on top of the tip of the snout and its eyes are on top of the head, so that when completely submerged except for those four inconspicuous bumps, the sly creature can breathe comfortably while watching all around it. The air passage from the nostrils to the throat and lungs can be closed by a flap, enabling it to seize an animal under water or remain there several hours without drowning.

Alligators dig deep caves, sometimes 40 feet long, with an entrance below the surface of a favorite pool or stream, where they retreat from danger and spend the winters. During the spring mating period both sexes, especially the males, wander from place to place. Then, at night, the bulls are very noisy. Their bellow is a deep booming roar that can be heard a mile away.

The female builds her nest on a spot of high ground, gathering fresh vegetation, trash and mud which, with her snout and belly, she fashions into a mound which may be three feet high. In this she lays several dozen long leathery eggs and, for two months, jealously guards them while they are incubated by the heat of the sun and decaying debris. when they are ready to hatch, and the young make grunting noises inside their shells, she tears off the top of the nest so that they may escape and forage for themselves. Few survive the first year, most of them being eaten by other creatures of the swamp.

An alligator grows rapidly. By the end of the first year, it is about 18 inches in length. In five years it may become six feet long. Until then, in many Florida counties, an alligator may not legally be captured nor hunted for its valuable hide. In the 1700's the naturalist, William Bartram, reported alligators so thick in the St. Johns River, Florida, that he could have crossed that broad stream by walking on their backs and some measured 20 feet in length. Nowadays their numbers have been greatly reduced and few get to be more than 10 feet long. Unless it is teased, or guarding its nest, an alligator will rarely attack a person.

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