The two reptiles are close relatives. But crocodiles tend to live in saltwater habitats, while alligators hang out in freshwater marshes and lakes. This smiley creature is an alligator.
Alligators have wider, U-shaped snouts, while the front end of a croc, like this one, is more pointed and V-shaped.
When their snouts are shut, crocodiles look like they're flashing a toothy grin, as the fourth tooth on each side of the lower jaw sticks up over the upper lip. For alligators, like this one, the upper jaw is wider than the lower one, so when they close their mouths, all their teeth are hidden.
A rare albino alligator lacks the pigments that make his relatives gray and green.
Crocodiles can eat meals weighing 23 percent of their body mass.
Efforts to reintroduce Chinese alligators, a critically endangered species, into its native habitat have scored a success: baby alligators.
A study reveals that up to 70 percent of female alligators returned to the same mate for several years.
An alligator suns itself at St. Marks National Wildlife Refuge in Florida.
An American alligator fights with an invasive python in Everglades National Park. The gator appears to be winning, but pythons sometimes come out ahead in these struggles and have even eating alligators.
A Burmese python (Python molurus) peeks over the head of an alligator that holds the python's body in its mouth in Everglades National Park. Invasive pythons have clashed with gators in Florida, sometimes eating the toothy reptiles.
This American alligator could easily go unnoticed swimming in the dark waters of Big Cypress National Preserve, Florida.
This large alligator was spotted lurking in Anahuac, Tex.
Chinese alligator, called Alligator sinensis, in the Yangtze River.
The dwarf crocodile O. tetraspis eats a captures a land crab at Loango National Park, Gabon.
The ancient crocodile relative Pakasuchus kapilimai likely snagged insects and small mammals for food. (Shown here in an artist's rendering.)
Among crocodilians, Crocodylus rhombifer (shown here) is one of the world’s most endangered species with the smallest natural distribution. In Cuba, the species coexists with the American crocodile (Crocodylus acutus).
Nile crocodiles are among the fiercest predators in the Okavango Delta, Botswana, yet their population has shrunk due to habitat loss and hunting. Dr. Alison Leslie of University of Stellenbosch suggests that climate change will be a further setback to crocodile numbers.