Let’s learn about alligators and crocodiles

These reptiles belong to the order Crocodylia, and their relatives go back more than 80 million years

Is this an alligator or a crocodile? To find out, you might need to get closer.

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It’s a log! It’s a rock! It’s a … crocodile? Or is it an alligator? How can you tell?

Alligators and crocodiles are both from the same order — or group of animals with similar characteristics. That order is Crocodylia. The crocodilian order is very ancient. The first ancient crocodile relatives walked the Earth more than 80 million years ago, though their ancestors have been around a lot longer. Crocodilians shared the world with dinosaurs and survived ice ages.

All modern crocodilians are long, scaly animals with stumpy legs and toothy grins. They are all semi-aquatic — spending time on land and in the water. And while some ancient crocodiles might have specialized in vegetable diets, modern crocodiles are meat-eaters.

But there are some differences. Alligators have wide, blunt heads with a rounded U-shaped snout. They tend to be darker than crocodiles and are less likely to be aggressive. When their mouths are closed, you can only see their upper teeth pointing down. They prefer to live in freshwater wetlands, though they have also been caught snacking on sharks in saltwater.

Crocodiles have longer, V-shaped snouts, and tend to be paler in color than alligators. They prefer living in saltwater and are more aggressive than alligators. When they close their mouths, they still have a toothy grin — their bottom teeth stick out and up. And while alligators are found only in the United States and China, crocodiles are found all over the world.

Some crocodiles make caring parents. Mugger crocodile dads look after their young for about a year after they are born.

Want to know more? We’ve got some stories to get you started:

American crocs seem to descend from kin that crossed the Atlantic: A fossil hints that early crocodiles crossed over from Africa, millions of years ago, to colonize a new land. (8/25/2020) Readability: 8.1

Ancient crocodiles may have preferred chomping plants, not meat: Fossil teeth of ancient crocodilians suggest that some ate plants, and that those green diets evolved in crocs at least three times more than 60 million years ago. (7/29/2019) Readability: 7.9.

Alligators aren’t just freshwater animals: It’s time to change the textbooks. Alligators have been seen in salty waters snacking on sharks. (12/6/2017) Readability: 7.2

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Alligators and crocodiles are known for the time they spend in wetlands, such as Everglades National Park in Florida. Wetlands might seem kind of flat and, well, wet. But in places like the Everglades, the smallest hills become mountains. Check out the Everglades National Park video series on wetland habitats.    

Bethany Brookshire is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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