What Is the Difference Between an Alligator and a Crocodile?

What Is the Difference Between an Alligator and a Crocodile?

Alligators and crocodiles both belong to the crocodilian class of reptiles, which has 24 species, but only two are found in the United States, the American Alligator and the American Crocodile.  The American Alligator can only be found within the United States, whereas the American Crocodile is more common in countries to the south.  Though many people may think alligators and crocodiles are pretty similar, they actually have many differences that clearly mark them as distinct species. Here we explore the differences between the American Alligator and the American Crocodile.

Physical Differences Between Alligators and Crocodiles

Snout. The easiest way to tell an alligator apart from a crocodile is to look at their snouts.  American Alligators have a U-shaped jaw with a broad snout. American crocodiles have a narrower snout with a V-shaped jaw.

Teeth. Differences can also be seen in the teeth of the two species. The teeth on the alligator’s upper jaw are exposed when its mouth is closed. Crocodiles have the fourth tooth on the bottom jaw exposed when their mouth is closed.

Coloring. The reptiles’ coloring also sets them apart.  The American Alligator adult is black with yellow or white crossbands on the back and tail. The American Crocodile adult is tan to dark brown with darker crossbands on the back, sides, and tail.

Bone Size. A new study has recently found that the humerus and femur bones of a crocodile’s limbs are slightly longer than the alligator’s.

Habitat Differences Between Alligators and Crocodiles

Special glands. You can’t see this difference, but crocodiles have special salt-excreting glands on their tongues responsible for getting rid of excess salt.  This special gland allows the crocodile to live in both freshwater and saltwater.  Alligators do not have this gland, so they prefer freshwater habitats.

Cold Tolerance. The alligator is more tolerant to colder temperatures than the crocodile.  Because of this, you can find alligators further north, whereas crocodiles tend to choose consistently warmer climates. For example, in the US, you can find alligators as far north as North Carolina, whereas you will only find crocodiles at the southern tip of Florida. In fact, southern Florida is the only place where the two species coexist.

Behavioral Differences Between Alligators and Crocodiles

Nesting Behavior. The alligator and the crocodile also differ in their nesting behaviors.  The crocodile will generally dig a hole and make a nest or create a mound, but she buries her eggs within the nest.  She then leaves the nest unattended until the eggs are ready to hatch, at which time she will return and dig up the eggs. On the other hand, the alligator builds a nest mound, lays her eggs, and vehemently defends her nest for the whole of the incubation period.

Territorial Behavior. The male American Crocodile systematically patrols his territory. The male American Alligator does not.

Mating Behavior. The mating rituals between the two species are also quite different.  The male American Alligator will bellow to gain the attention of a female while the male American Crocodile remains silent but head slaps. Both the male and the female alligator participate in signaling behavior in contrast to the crocodile, which exhibits sex-specific behaviors. The female crocodile is also more submissive than her female alligator counterpart. 

Resources

Encyclopedia Britannica – “What’s the Difference Between Alligators and Crocodiles?”

“San Diego Zoo’s Animal Bytes: Alligator & Crocodile.”

Garrick, Leslie D. et al. “Social Signals and Behaviors of Adult Alligators and Crocodiles.” American Zoology. 1977. Vol. 17. Pp: 225-239.

Lijima, Masaya. “Comparative Limb Proportions Reveal Differential Locomotor Morphofunctions of Alligatoroids and Crocodyloids.” Royal Society Open Science. 2018. Web. 19 December 2019. https://royalsocietypublishing.org/doi/full/10.1098/rsos.171774

Cramp, Rebecca L. et al. “Functional and Morphological Plasticity of Crocodile (Crocodylus Porosus) Salt Glands.” Journal of Experimental Biology. 2008. Vol. 211. Pp: 1482-1489.

Mazzotti, Frank J. et al. “Large Reptiles and Cold Temperatures: Do Extreme Cold Spells Set Distributional Limits for Tropical Reptiles in Florida?” Ecosphere. An ESA Open Access Journal. 2016. Web. 19 December 2019.

National Wildlife Foundation – “American Alligator.”

National Park Service – “American Crocodile: Species Profile.”

The University of Georgia – Savannah River Ecology Laboratory – “American Alligator (Alligator mississippiensis).”