Crocodiles And Alligators

Crocodiles & Alligators

Scientific Classification

Common Name
crocodile, croc; alligator, gator
Crocodylidae (crocodiles), Alligatoridae (alligators)
Genus Species
23 living species

Fast Facts

Crocodilians are large, lizard-shaped reptiles with four, short legs and a long, muscular tail. Their hide is rough and scaled.
The difference between alligators and crocodiles is often easy to spot once you get the hang of it. Alligators are dark colored with a broad, rounded snout and are usually found in fresh water. Crocodiles are grayish-green and prefer coastal, brackish and salt-water habitats. They have a narrow, tapered, triangular snout. Also, the fourth tooth on either side of the lower jaw of an alligator fits into an internal socket in the upper jaw so that these teeth are hidden when the mouth is closed. In a crocodile, the fourth tooth is always exposed.
Male: For all species of crocodilian, mature males grow larger than females.
The largest species of crocodilian is the saltwater crocodile, Crocodylus porosus, which can measure more than 6 m (20 ft.). The smallest species is the Cuvier's dwarf caiman; adult males only reach a maximum length of about 1.6 m (5.2 ft.).
900-1360 kg (1-1.5 tons) maximum; most species approximate 454 kg (0.5 ton) or less
Crocodilians are predatory and depending on their size and habitat may feed upon a variety of fishes, reptiles (including other crocodilians), amphibians, aquatic invertebrates and even birds, mammals and carrion.
No data
Clutch Size: No data
Breeding Period: No data
Sexual Maturity
No data
Life Span
Probably very long-lived - at least 50 to 60 years.
Two species of crocodilians are native to the United States - the American alligator (Alligator mississippiensis) and the American crocodile (Crocodylus acutus). American alligators are restricted to the southeastern United States, while the highly endangered American crocodile is found only in the southern tip of Florida.
Mostly found in tropical and subtropical freshwater and saltwater habitats.
Global: No data
IUCN: 13 species are listed, 4 of which are listed as critically endangered
CITES: Nearly all species of crocodilians are listed
USFWS: The American alligator is listed as threatened and the American crocodile as endangered. Many other species are listed.

Fun Facts

  1. Alligators and crocodiles are one of the oldest and most successful groups of predators. A noteworthy extinct crocodile was Deinosuchus, or "terrible crocodile." The only fossil recovered from this species was a skull found in Texas, which measured more than 2 m (6.6 ft.) in length. Based on this skull size, researchers believe this enormous predator was 15 m (49 ft.) long and large enough to eat most dinosaurs living at the time.
  2. Crocodilians, like the American alligator, have vertical pupils that open wide in low light, which allows them to be impressive nocturnal hunters. Their throat (gular) pouch blocks water so that they can eat prey under water as well as on land.
  3. The 23 living species of crocodilians have changed little since the appearance of their prehistoric relatives, although this does not mean they are not advanced compared to other reptiles. Unlike other living reptiles, for example, crocodilians have efficient four-chambered hearts (like birds and mammals).

Ecology and Conservation

Crocodilians are vital to the overall health of their ecosystems. For example, Nile crocodiles (Crocodylus niloticus) control the barbel catfish population. If crocodiles were hunted to extinction, the voracious catfish could wipe out other fish populations, which are food sources to more than 40 species of birds. The birds, in turn, are necessary because their droppings recycle nutrients back into the system. Crocodiles are also scavengers that feed on dead carcasses found along the waterways, effectively cleansing the environment. Without crocodilians, many ecosystems would suffer.


Conant, Roger and Joseph T. Collins. Reptiles and Amphibians: Eastern and Central North America. Boston. Houghton Mifflin Co., 1991. 

Haliday, T. and K. Adler, eds. Encyclopedia of Reptiles and Amphibians. New York: Facts on File, Inc., 1987.

Ross, C., ed. Crocodiles and Alligators. New York: Facts on File, Inc., 1989.

Steel, Rodney. Crocodiles. London. Christopher Helm Ltd., 1989.