Alligators are not amphibians, they are reptiles. Alligators belong to the order Crocodilia within the Reptilia class of animals, whereas amphibians belong to the order Lissamphibia inside the Amphibia class.
There are many physical differences between reptiles and amphibians, the most notable being that juvenile amphibians go through a larval stage before metamorphosing into their adult forms, whereas reptiles don’t.
What is an Amphibian?
An amphibian is a class of animals that includes frogs and salamanders. Amphibians are tetrapods, lay their eggs in water, and are born with gills which disappear after their metamorphosis into their adult forms.
Within the Amphibia Class, there are three major taxa. These are the anurans, the caudates, which is also referred to as the urodeles, and the gymnophiones.
Anurans are frogs and toads, while caudates are the salamanders and newts. The gymnophiones are limbless caecilians—these are serpentine amphibians that look like worms. Amphibians are old; they have been around since the Mesozoic Era, about 250 million years ago.
What are Reptiles?
A reptile is an air-breathing vertebrate that belongs to the Reptilia class of animals. Reptiles are characterized by their epidermic scale. Some give live birth, but most lay eggs.
The most common reptiles are lizards, snakes, and the crocodile family. There are several groups of reptiles, as shown below:
- Testudines – these are the turtles
- Rhynchocephalia – an example is a tuatara
- Squamata – snakes and lizards
- Crocodylia – crocodiles, alligators, caimans, and gharials
There are over 8,700 species of reptiles, and they share a common ancestor with birds. Both birds and reptiles share a common ancestor with dinosaurs, the Archosaur.
Related Article: How Fast Can Alligators Swim?
Alligator and Amphibian Differences
Below is a list that shows the difference between an alligator and an amphibian.
| Amphibians | Alligators | |
|---|---|---|
| Class | Amphibia | Reptilia |
| Lungs | Juveniles have gills, adults have lungs | Air-breathing lungs |
| Eggs | Jelly eggs laid in water | Hard eggs laid on land |
| Habitat | Semi-aquatic, freshwater only | Semi-aquatic, fresh and salt water |
| Skin | Smooth, covered in mucus | Rough, covered in bony scales |
1. Lungs
Both alligators and amphibians have lungs. However, alligators are born (or hatched) with lungs. Amphibians are hatched with gills.
The amphibian will spend its juvenile years in water—breathing oxygen with its gills. Alligators are not like this. While they spend a lot of time in the water as juveniles, they need to surface to get air. As the amphibians grow, they lose their gills and develop lungs.
Read More: Why Are Alligators Not Considered Lizards?
2. Egg Fertilization
Alligator eggs are fertilized internally, while amphibian eggs are fertilized externally. What happens with amphibians is that the mother will lay the egg in the water, and then the father will fertilize it. They do not have sex.
Alligators, on the other hand, have to mate to fertilize the egg. Once the mother alligator is ready, it will lay its eggs in a nest in a dry land.
3. Habitat
While both alligators and amphibians thrive underwater, the alligator has a much more diversified habitat. The crocodile’s cousin can live in saline water, but amphibians cannot do this.
Amphibians only live in freshwater. As a juvenile, the amphibian will spend its young years in a pond, lake, or river. It cannot breathe air at this time. Once it matures, it will step out of the water to breathe air.
4. Skin
Alligators have scales, and bony plates called scutes. Amphibians do not have this. Amphibians have soft skin that is moist with mucus. Not all amphibians have smooth skin.
Toads, for example, have rough skin because they have exposed glands that produce toxic materials. For example, the cane toad produces toxins powerful enough to poison a snake.
5. Breathing
The alligator breathes air using its lungs. However, the process it uses is different from how humans breathe. Humans breathe bidirectionally. Alligators, like birds, breathe unidirectionally.
Amphibians, on the other hand, breathe two ways. They breathe through their lungs and skin. Their skin has to stay wet to be able to absorb oxygen—it is why they secrete mucus all the time. If the skin gets too dry, they will die.
When amphibians breathe through the skin, the oxygen gets absorbed into the blood vessels. Sometimes, more than a quarter of the total oxygen that they breathe is processed through the skin.
6. Metamorphosis
All amphibians go through a period of metamorphosis, when the larvae develops into a full adult, losing its gills and leaving the water for the first time.
As far as metamorphosis goes, the best example is the tadpole. It hatches from its egg without limbs. As it grows, it grows, legs, and loses its tail. By the time it becomes an adult frog, it looks completely different from what it used to be.
Alligators do not go through metamorphosis. Once they hatch, they only increase in size. Some change their colors as they get older, but the way they look is still generally the same, and they keep their long tail which helps them to swim faster, but prevents them from walking bipedally.
Can Alligators Become Amphibians?
Alligators can not become amphibians. Alligators and amphibians have been evolving separately, diverging from their common ancestor for hundreds of millions of years.
Evolution is about abnormalities that happen in the genes. As the genes stay in the bloodline, they serve as a building block for what will later become tissue or organ.
If a species never had this founding or building block, then there is no way it could build a tissue that another species has.
Related Article: Are Alligators Carnivores?
Do Alligators Breathe Underwater?
Alligators can not breathe underwater. Alligators do not have gills, so they need to use their lungs to breathe in air to stay alive. Although they can’t breathe underwater, they can hold their breath for up to 24 hours.
Alligators can stay underwater for as long as 24 hours. The average, however, is only 15 minutes. The 24- hour duration is a stretch.
When alligators stay underwater, they reduce their heartbeat by two to three times a minute. Since they don’t use a lot of energy, they don’t also need to use a lot of oxygen.
Related Article: Do Alligators Eat Fish?
Summary
Alligators are not amphibians; they are reptiles. While both reptiles and amphibians are cold-blooded, they have several differences.
Amphibians go through metamorphosis while reptiles don’t. Amphibians can breathe through their skin, but alligators and reptiles cannot. Reptiles require fertilization inside the body, but amphibians do it externally.
Alligators cannot breathe underwater—they have to go back to the surface to get air. As reptiles, they have lungs, and the only way to breathe is through it, but not through the skin like amphibians do.
Stuart is the editor of Fauna Facts. He edits our writers’ work as well as contributing his own content. Stuart is passionate about sustainable farming and animal welfare and has written extensively on cows and geese for the site.