28 April 1998

Alligators and crocodiles do look similar but there are several physical characteristics that differentiate the two giant reptiles. Scientists separate alligators, crocodiles, and their cousins, caimans and gharials, according to differences in their skulls, scales, and teeth. The most easily observed difference between alligators and crocodiles is the shape of the head. The crocodile's skull and jaws are longer and narrower than the alligator's.

The American alligator, Alligator mississippiensis, resides primarily in the rivers and wetlands in the southeastern region of North Carolina, but can also be found as far north as the Albemarle Sound. Coastal North Carolina is the northern most range for the American alligator.

In both alligators and crocodiles, the fourth tooth on either side of the lower jaw is exceptionally long. When an alligator closes its mouth, those long teeth slip into sockets in the upper jaw and disappear. When a crocodile closes its mouth, the long teeth remain visible, protruding outside the upper jaw. In general, if you can still see a lot of teeth even when the animal's mouth is closed, you are looking at a crocodile. Alligators have plenty of teeth, but fewer show until the mouth is open.

Like sharks, crocodilians never run out of teeth, for sharp new ones grow in as old dull ones are shed throughout the animals' lives. Numerous as they are, crocodilian teeth serve only for grasping, not chewing. These animals gulp their food in large chunks and rely on powerful stomach acids to break it down.

Alligators and crocodiles both have thick, bumpy skin but alligators tend to be darker in color. Adult alligators are grayish black while adult crocodiles are light tan to brown in color. Young alligators can be more colorful with yellow or white highlights on a black body.

Another difference between crocodiles and alligators is their choice of homes. Alligators are freshwater reptiles, favoring the rivers, lakes, swamps, and marshes of the coast. On the other hand, crocodiles prefer coastal, brackish, or salt water habitats.

Crocodilians belong to the subclass Archosauria ("ruling reptiles"), which dates back over 180 million years and includes the vanished dinosaurs. As far as we know, crocodilians are the only true archosaurs remaining alive today.

Two crocodilians are native to the U.S., the American alligator and the American crocodile. The range of the American alligator, found only in the Southeastern part of the country, is restrained by cold temperatures and distribution of wetlands. The American crocodile is even more sensitive to cold; its range is limited to tropical areas. The American crocodile is very rare and in the U.S. can be found only in the southern tip of Florida.

Both alligators and crocodiles are protected by state and federal laws. The alligator is listed as a threatened species and the crocodile as endangered under the federal Endangered Species Act.