Alligators and crocodiles belong to the order Crocodylia, a group of large, ancient reptiles that often look indistinguishable to the untrained eye. These semi-aquatic predators trace their lineage back over 200 million years. Alligators (family Alligatoridae) and crocodiles (family Crocodylidae) diverged roughly 80 to 100 million years ago, developing distinct features suited to their environments. Understanding the differences in their physical anatomy, particularly the head, provides reliable methods for telling these powerful creatures apart.
The Shape of the Snout
The most immediate difference between these two animals is the shape of their snout. Alligators possess a broad, rounded, U-shaped snout that resembles a shovel. This wider jaw structure is advantageous for crushing prey, such as hard-shelled turtles and large land animals common in their swamp habitats.
Crocodiles, in contrast, feature a narrower, pointed, V-shaped snout that is more wedge-like. This elongated shape is better suited for quick, snapping motions, making it highly effective for catching fast-moving prey like fish. The visual comparison is often the quickest way to categorize the animal, though exceptions exist, such as the broader-snouted Mugger crocodile.
These different snout shapes reflect distinct feeding strategies. The alligator’s wide jaw provides powerful crushing force to break through rigid defenses. The crocodile’s slender jaw prioritizes speed and precision for grabbing slippery aquatic prey.
Telling the Difference by Teeth
Identification also involves examining the arrangement of their teeth when the mouth is closed. Alligators have an overbite because their upper jaw is slightly wider than the lower jaw. This structure allows the upper row of teeth to completely conceal all of the lower teeth when the mouth is shut.
When an alligator closes its mouth, the lower teeth fit neatly into sockets in the upper jawline, resulting in a clean, smooth-looking jaw. Only the upper teeth are visible along the margin of the mouth.
Crocodiles, however, have upper and lower jaws that are nearly the same width, causing the teeth to interlock when the mouth is shut. Teeth from both the upper and lower jaws remain visible, protruding along the jawline. The most reliable dental indicator is the large fourth tooth on the lower jaw, which is always exposed and fits into a notch on the outside of the upper jaw, giving the crocodile a snaggle-toothed appearance.
Habitat and Location Clues
The environment offers a further clue to identity, especially regarding tolerance for salt water. Alligators primarily inhabit freshwater environments, such as swamps, marshes, and lakes, due to their relatively ineffective salt glands.
Crocodiles possess specialized salt glands on their tongues that allow them to excrete excess salt. This adaptation allows many species to thrive in brackish water and saltwater marine environments, such as coastal estuaries. This difference gives crocodiles a much wider global distribution across tropical regions in Africa, Asia, Australia, and the Americas.
Alligators are geographically restricted to the United States and China. American alligators are concentrated in the southeastern US, while the Chinese alligator is found only in the lower Yangtze River basin. The only region where both alligators and crocodiles coexist naturally is a small area in southern Florida.