Why Crocodiles Aren’t Considered Marine Mammals

Crocodiles are not mammals, they are semi-aquatic reptiles. Crocodiles and other reptiles belong to the Reptilia class of animals and are typically cold-blooded, scaled, egg-laying animals whereas mammals belong to the Mammalia class and are warm-blooded, covered in fur, and give birth to live young.

Reptiles are cold-blooded creatures with scales or plates, and they lay eggs. Crocodiles are vertebrates because they have a backbone.

Why Crocodiles Aren't Considered Marine Mammals

What is the Difference between Reptiles and Mammals?

According to National Geographic, mammals are warm-blooded organisms with backbones (known as vertebrates) that nourish their young with milk and have highly developed brains.

Reptiles are vertebrates, like mammals and birds, except they are cold-blooded. Reptiles’ skin is covered with scales or plates, and they typically lay eggs rather than give birth to live young.

Reptiles include crocodiles, alligators, chameleons, cobras, sea turtles, and rattlesnakes.

Thermal RegulationExternal (Cold-Blooded)Internal (Warm-Blooded)
Skin CoveringScales or PlatesFur
Birth MethodEggsLive Birth
Class (Taxonomy)ReptiliaMammalia

Since crocodiles are cold-blooded, have hard scales all over their bodies and lay clutches of eggs when giving birth, they clearly belong to the reptile class of animals.

Crocodiles and alligators look similar, although alligators are usually darker in color.

Similarities Between Crocodiles and Mammals

1. Crocodiles and Mammals are Tetrapods

Crocodiles and mammals are both tetrapods. Tetrapods are a group of vertebrate species defined as having four limbs, or having evolved from an ancestor species with four limbs.

2. Crocodiles and Mammals have Four-Chambered Hearts

All reptiles and amphibians have a three-chambered heart, with the sole exception of crocodiles. Crocodiles are the only reptile to have a four-chambered heart similar to mammals and birds.

It’s thought that crocodiles evolved this more advanced heart to help them reduce the rate of circulation and increase the length of time they can spend underwater.

3. Crocodiles and Mammals Both Breathe Air

Both Crocodiles and mammals have air-breathing lungs and are unable to breathe underwater.

Unlike fish and juvenile amphibians, crocodiles can not extract oxygen from water as they lack gills.

In this respect, crocodiles are more similar to marine mammals than to fish or amphibians.

Is a Crocodile a Marine Mammal?

Crocodiles are not marine mammals, they are semi-aquatic reptiles. Crocodiles cannot breathe underwater and must come to the surface to breathe, reproduce, sleep, and eat.

Distinct crocodilian species spend a different balance of time on land and time in the water, with saltwater crocodiles leaning more toward the aquatic edge, staying prolonged periods at the water. They, too, come to land occasionally to bask and lay eggs.

Marine mammals include orcas, whales, seals, and otters. Semi-aquatic reptiles include crocodiles and alligators, turtles, and some snakes.

Is a Crocodile Considered a Mammal or an Amphibian?

Crocodiles are not considered amphibians or mammals, they are reptiles.

Amphibians are born in water whereas crocodiles and mammals are born on land. Crocodiles lay hard eggs on land, whereas mammals give birth to live young, and amphibians lay jelly-eggs in water.

Juvenile crocodiles and mammals are similarly formed to their adult counterparts, whereas amphibians are born as larvae and undergo metamorphosis.

Why are Crocodiles Not Classified as Mammals?

Crocodiles are not considered mammals because they lack the defining characteristics of mammals. For example, crocodiles are not warm blooded, they don’t give birth to live young, they are not covered in hair, and they do not produce milk.

The crocodilia order of animals contains all crocodiles and alligators and belongs to the reptile class of animals.

Crocodiles are descended from the reptile classification, but have formed a distinct branch of the evolutionary tree. Crocodiles have four-chambered hearts, unlike any other reptile.

Read More: Every Type of Crocodile Explained

Is a Crocodile a Marine Reptile?

Although crocodiles spend some time in the water, most crocodiles still spend time on land for breeding, basking, eating, and reproducing. As such, they are considered semi-aquatic reptiles, not marine reptiles.

Other semi-aquatic reptiles include turtles, some iguanas, and some snakes that spend considerable amounts of time in water but ultimately must return to land to breed.

Is a Crocodile an Egg-Laying Mammal?

Crocodiles lay eggs, but they are not mammals. The only currently extant egg-laying mammal species are the platypus (Ornithorhynchus anatinus) and the Echidna (Tachyglossidae).

Crocodiles are reptiles, and lay hard-shelled protective eggs.

Do Crocodile eat Mammals?

Crocodiles consume a wide variety of species, including huge ungulates, medium-sized birds, mammals, and small reptiles. While crocodiles spend most of their time in the water, they are also capable of hunting on land.

Although they are powerful enough to kill huge animals, they prefer to feed on medium-sized or smaller mammals. Young crocodiles are unable to capture big creatures, including zebras, because their strong kick quickly crushes the croc’s jaws. As a result, adult crocodiles must accomplish this on their own.

Crocodiles are commonly referred to be “sit-and-wait predators” because they wait for the proper opportunity to strike their prey. They usually remain still in the water while focusing on the prey.


A crocodile is a reptile due to its hard, bony plates and scales. They cannot regulate body heat as they are cold-blooded creatures, whereas mammals are warm-blooded. In addition, they don’t have mammary glands, so they aren’t classified as mammals.

There are many differences between mammals and crocodiles. Crocodiles lay eggs on land instead of giving birth to their young ones. They do not have milk glands so they cannot feed milk to their babies. They have tough, scaly skin in place of body hair and fur.

Although crocodiles resemble amphibians, the major difference is that amphibians can respire in bad conditions since their skin is usually moist, whereas crocodiles cannot.

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