Alligators vs. Crocodiles
Alligators and crocodiles are reptiles that appeared on the planet more than 100 million years ago. They belong to two different families: Alligatoridae, which includes 2 species of alligators and 5 species of caimans, and Crocodylidae, which includes 15 species of true crocodiles. Despite many common features, alligators and crocodiles can be easily distinguished from one another by:
Geographical Distribution and Habitat
Crocodiles can be found in Africa, Asia, Australia and Americas. They usually reside in tidal estuaries, brackish waters and areas near the sea coast. Unlike crocodiles, alligators inhabit only southeastern parts of the USA and China. They prefer freshwater habitats such as rivers, marshes and lakes.
Crocodiles can survive in salty water thanks to salt glands on the tongue, designed to eliminate excess salt from the body. Alligators also possess these glands, but they are not functional (they've lost their function during evolution).
Color of the Skin
Both alligators and crocodiles have thick, bumpy skin. Most species of crocodiles are yellowish-brown or light brown colored, while alligators have darker, grayish-black skin.
Shape of the Snout
Shape of the snout is the most prominent feature, that can be used to distinguish crocodiles from alligators. Crocodiles have elongated, narrow head with pointed, V-shaped snout, while alligators have short head with wide, U-shaped snout. Crocodiles have slightly weaker jaws, designed for killing different types of soft-bodied animals (usually fish). Wide, shovel-like jaws of alligators can easily crush shells of turtles and other aquatic invertebrates. Unlike crocodiles, alligators occasionally consume leaves and fruit.
Visibility of Teeth
Crocodiles and alligators have large number of strong teeth that are used for gripping and tearing big chunks of meat off the victim's body. Just like sharks, they constantly replace old teeth with new ones throughout their life. Lower jaw of alligators and crocodiles is equipped with two very long teeth (4th tooth on both sides of the lower jaw). These teeth are always visible in crocodiles (even with closed mouth). Unlike crocodiles, alligators have wide upper jaw filled with small depressions (sockets) which hide all teeth in the lower jaw (including the pair of very long teeth) when the mouth is closed.
Number of Dermal Pressure Receptors
Crocodiles and alligators have small, black dots on the edges of the scales, which detect small changes in the pressure of the water and facilitate detection of food. These sensory organs are also known as dermal pressure receptors. Entire body of crocodiles (all scales) is equipped with dermal pressure receptors. Unlike them, alligators have dermal pressure receptors only on the scales around jaws.
Morphology of Legs and Feet
Alligators have webbed feet, while crocodiles have jagged fringes on the hind legs and feet.
And finally, based on the number of attacks in the wild and in the zoos, crocodiles are labeled as "more aggressive" than alligators.