What is the difference between alligators and crocodiles?
28 April 1998
Alligators and crocodiles look similar, but there are several physical characteristics that differentiate the two giant reptiles.
Scientists separate alligators and 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.
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. 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. Adult crocodiles are light tan to brown. 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 rivers, lakes, swamps and marshes of the coast. Crocodiles prefer brackish or saltwater habitats in coastal zones.
Crocodilians belong to the subclass Archosauria (“ruling reptiles”), which dates back more than 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.