alligator, large aquatic reptile of the genus Alligator, in the same order as the crocodile. There are two species—a large type found in the S United States and a small type found in E China. Alligators differ from crocodiles in several ways. They have broader, blunter snouts, which give their heads a triangular appearance; also, the lower fourth tooth does not protrude when the mouth is closed, as it does in the crocodile.
The American alligator, Alligator mississipiensis, is found in swamps and sluggish streams from North Carolina to Florida and along the Gulf Coast. When young, it is dark brown or black with yellow transverse bands. The bands fade as the animal grows, and the adult is black. Males commonly reach a length of 9 ft (2.7 m) and a weight of 250 lbs (110 kg); females are smaller. Males 18 ft (5.4 m) long were once fairly common, but intensive hunting for alligator leather eliminated larger individuals (a specimen over 10 ft/3 m long is now unusual) and threatened the species as a whole. The wild American alligator is now protected by law, but it is also raised on farms for commercial uses.
Alligators spend the day floating just below the surface of the water or resting on the bank, lying in holes in hot weather. They hunt by night, in the water and on the bank. Young alligators feed on water insects, crustaceans, frogs, and fish; as they grow they catch proportionally larger animals. Large alligators may occasionally capture deer and cows as they come to drink; they do not commonly attack humans. Alligators hibernate from October to March. In summer the female builds a nest of rotting vegetation on the bank and deposits in it 20 to 70 eggs, which she guards for 9 to 10 weeks until they hatch.
The Chinese alligator, A. sinensis, which grows to about 6 ft (1.8 m) long, is found in the Chang (Yangtze) River valley near Shanghai. This species is nearly extinct. Caimans are similar, but distinct members of the Alligatoridae family found in Central and South America. There are several species, classified in three genera. The largest grow up to 15 ft (4.8 m) long. Unlike alligators, caimans have bony overlapping scales on their bellies. Baby caimans are often sold in the United States as baby alligators.
Alligators and caimans are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Crocodilia, family Alligatoridae.