What's the Difference Between Alligators and Crocodiles?

Most of us aren’t going out of our way to get up close and personal with any large-toothed reptiles. But on the off chance you find yourself zipping through the coastal wetlands of the southeastern United States or the tropical climates of northern Australia, you may want to know the difference between alligators and crocodiles.

Alligators and crocodiles belong to different families. Although these animals may look identical at a glance, there are several distinguishing characteristics—from the snout shape and teeth position to coloring and habitat—that make it easy to tell them apart. Learn more about these characteristics, as well as which alligator and crocodile species are critically endangered.

Alligator and Crocodile Classification

Alligators and crocodiles both belong to the taxonomic order Crocodylia. From there, the order is split up into three separate families: Alligatoridae (alligators and caimans), Crocodylidae (crocodile), and Gavialidae (gharial and the false gharial).  

The two major groups, Alligatoridae and Crocodylidae, are believed to have split during the Late Cretaceous period between 100 and 66 million years ago, meaning they survived the asteroid that wiped out the dinosaurs. In fact, early semi-aquatic ancestors to crocodylians, such as the almost 40-foot-long Sarcosuchus imperator, could reach weights of 17,000 pounds and likely preyed on dinosaurs.

Today, the scientific community recognizes 26 extant Crocodylia species, including eight species of Alligatoridae and 16 species of Crocodylidae.

How to Tell the Difference Between Alligators and Crocodiles

Distinguishing the shape of the snout is one of the easiest way to tell the difference between alligators and crocodiles. The alligator snout is broad and rounded into a U-shape, while crocodile species have narrower, V-shaped snouts. Crocodiles also have visible lower and upper teeth when their mouths are shut, unlike alligators, whose lower teeth are hidden.

Both alligators and crocodiles are typically found in freshwater areas like swamps, rivers, streams, and lakes. However, some crocodiles have adapted to live in fresh and saltwater environments thanks to their ability to regulate salt. The saltwater crocodile, for example, is the world’s largest living reptile and native to wetlands and coastal regions along the eastern Indian and western Pacific oceans. The Florida Everglades is the only place where both crocodiles and alligators exist together in the wild.

Both of these fascinating reptiles are incredibly strong, but crocodiles are generally considered to be more aggressive animals. Crocodile adults can grow to more than 20 feet long, while alligators max out at around 14 feet. Depending on their surroundings, gators are usually dark gray, dark green, or black in color, while crocodiles are lighter green, grayish brown, or tan.

Scientists recently discovered that the two reptiles have slight differences in their limbs, which can affect their speed and movement. Alligators have shorter humerus and femur bones in their forelimbs and hind limbs than crocodiles, a small but mighty difference in otherwise remarkably similar biology.

Conservations Status

American alligators were once famously threatened by extinction from habitat loss and development, earning them a place on the endangered species list in 1967. Thanks to conservation efforts, however, the species is now classified as Least Concern. Other species haven’t had as much luck. The Chinese alligator, once widely distributed in the lower Yangtze River system in southeastern China, is critically endangered due mainly to habitat loss and hunting.

In 2022, a comprehensive study conducted by the International Union for Conservation of Nature found that 50% of all crocodile species were in danger of becoming extinct within 10 years or three generations. Of all crocodile species assessed by the IUCN, five are critically endangered: the Philippine crocodile, the Orinoco crocodile, the Siamese crocodile, the Cuban crocodile, and the African slender-snouted crocodile. The Philippine crocodile (of which an estimated 92 to 137 remain) was one of the original 181 species assessed using the IUCN Green Status of Species, a Global Standard implemented in 2021 to more accurately measure conservation status and effectiveness.