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Why Crocodiles Aren’t Considered Amphibians

Crocodiles are not amphibians, they are reptiles. The main difference is that a reptile cannot use its skin as a secondary breathing system, whereas amphibians can. 

Muja the Alligator
Although crocodiles spend a lot of time in the water, they are not amphibians

Another easy way to tell that crocodiles are not amphibians is that amphibians go through a metamorphosis from birth to adulthood, while reptiles don’t.

What are Amphibians?

Amphibians are ectothermic animals, which means that they are cold-blooded. All of them belong to the taxonomic group Lissamphibia. Like many reptiles, they inhabit a wide range of habitats. 

Amphibians are not just aquatic. There are so many species that include: 

  • Arboreal –lives in trees
  • Terrestrial – lives in water 
  • Fossorial – lives underground in a burrow

Unlike reptiles, amphibians typically start as larvae in water. After some time, they grow into small animals and then go through a significant change. Not all amphibians do this, as some have bypassed this type of reproduction. 

A good example of this is the frog, the most known amphibian. Yet, throughout its life, it becomes several things. 

As an overview, here is the life cycle of a frog: 

  • Egg
  • Tadpole
  • Tadpole with hind legs
  • Froglet 
  • Adult frog

Reptiles do not go through metamorphosis. Once a reptile hatches, they are already in their final form. They will not change significantly, except for size.

An amphibian can breathe through its skin, apart from the lungs. It is why they can survive in water. Because of this, the amphibians’ skin must stay wet to be able to absorb the oxygen from the water. If the amphibian gets too dry, they will die. 

Some amphibians, like tadpoles, have gills like fish. In many amphibians, their gills are located outside their bodies, and are not covered. A good example of this is the salamander.

A tadpole swimming in a tank
Amphibians go through a larval stage before metamorphosing into their adult forms

Related Article: Do Crocodile Live in Water?

What are Reptiles?

Reptiles are cold-blooded, air-breathing, egg-laying tetrapods with bony scales or scutes that belong to the class Reptilia. Unlike amphibians, they can not breathe through their skin and they are born in their adult form without the need for a larval period.

Reptiles have another distinction from amphibians, as reptiles have scales that serve as protective armor. For crocodiles, the scales are called scutes. Some reptiles have bony plates, and some have both plates and scales. 

Read More: Crocodile Scutes Explained

The metabolism of a reptile depends on the temperature of the environment. Unlike mammals, reptiles cannot maintain a regulated body temperature. They also do not have sweat glands that allow them to pant. 

As such, reptiles like crocodiles must bask under the sun to get warm or hide in burrows if it gets too cold. They also have to move to the shade if it gets too hot. It is why it is not uncommon to see crocodiles, snakes, and turtles basking under the sun.

Another fascinating thing about reptiles is that their reproduction has a dependency on temperature. Many species of reptiles lay eggs and then leave.

Crocodiles are some of the most dangerous reptiles in the world.

A juvenile caiman on some reptile eggs
Reptiles lay eggs and are born in their adult form

Read Also: Do Crocodiles Have Long Tails?

Why are Crocodiles Not Amphibians?

Crocodiles are not amphibians because they do not possess the characteristics of one. A crocodile cannot breathe through its skin. What it has is a thick armor of scales and bony plates.

Crocodiles also do not breathe through their skin. They only breathe through their lungs. Although crocodiles can hold their breath for a long period, they cannot breathe underwater.

In addition to that, a crocodile does not go through metamorphosis. When a crocodile hatches, no significant changes happen to its body except growth. 

What is the Difference Between a Crocodile and an Amphibian?

The main differences between reptiles like crocodiles and amphibians are their breathing and their growth cycle. Amphibians can absorb oxygen from the water through their porous skin, whereas crocodiles require access to the air to breathe through their lungs. Amphibians are born as larvae and go through a metamorphosis to transform into their adult forms. Crocodiles do not go through this process.

AmphibiansCrocodiles
Thermal Regulation
Cold-blooded
Cold-blooded
RespirationAbsorbs oxygen from water or breathes through their lungs. Larvae have gills but they disappear as they age.Air-breathing lungs. Can not breathe underwater.
MetamorphosisMetamorphosis from larvae to adultNo metamorphosis period
EggsAmphibians lay jelly-like waterborne eggs which hatch into an aquatic larva.Crocodiles have no larval period and hatch from solid eggs laid on land.
FertilizationExternalInternal

When it comes to fertilization, one of the best examples is that of a frog. The female frog will lay its eggs in the water. Next, a male frog releases its sperm in the water to fertilize them. 

Scientists, however, discovered that some frogs do not do this kind of fertilization. They found out that some species of frogs use internal fertilization, too. The eggs are fertilized inside the frog, and then they are released. 

In addition to these differences, amphibians lay their eggs in water, holding them together by a gel. Reptiles, however, lay eggs like birds. A crocodile’s egg is both soft and hard. The outer part is hard for protection, while the inside is soft.  

Frogspawn
Amphibian eggs are soft and jelly-like and laid in water, whereas crocodile eggs are hard and laid on land

Related Article: Can Alligators and Crocodiles Be Pets?

Summary

Crocodiles are reptiles; while cold-blooded, they do not qualify as amphibians because they cannot breathe through their skin. They also do not go through metamorphosis. 

Crocodiles, being reptiles, have scales. Amphibians do not have scales. Also, crocodiles must live on land, while amphibians can live in water, even for part of their lives. 

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