Are Alligators Mammals? (Here’s Why They’re Reptiles)

No, alligators are not mammals. They are reptiles. As reptiles, they do not have mammary glands. They also do not give live birth—they lay eggs.

Alligators are descendants of the archosaur, a reptile that was purportedly the ancestor of reptiles and birds. It also includes sub-classes like dinosaurs and avian reptiles. Mammals, on the other hand, are descendants of reptiles.

Are Alligators Mammals

Differences between Mammals and Reptiles

Mammals are warm-blooded animals, while reptiles are cold-blooded. Mammals have mammary glands that produce and secrete milk.

Mammals have skin that has a hair covering. Reptiles do not have these two characteristics.

Reptiles have scaly skin. The alligators and their cousins, the caimans, gharials, and crocodiles, have thick protective armor called scutes.

There are about 5,500 species of mammals in the world, and they live in many types of habitats. There are mammals in the sea like the orcas, and there are mammals in deserts and rainforests, too. Mammals are huge, while reptiles are generally small.

However, some reptiles can grow big, like the alligators and pythons, and boas. Generally speaking, many gigantic reptiles are already extinct.

1. Reproduction

Mammals use internal fertilization. What this means is that the sperm fertilizes the egg inside the mother’s body.

The embryo develops into a baby. Because of this, most mammals give birth to a young that is almost already fully developed.

Reptiles, on the other hand, lay eggs. This is not to say that all of them lay eggs—some reptiles give birth to a young, as some snakes do. Mammals feed their young with milk. Reptiles do not do this. Instead, they feed their young with food.

Related Article: What US States Have Alligators?

2. Thermoregulation

Mammals are warm-blooded animals. What it means is that they can regulate their body temperature.

Reptiles cannot do this. To achieve an ideal temperature, the reptile must do something, like bask in the sun or go for a swim.

Mammals are not the only warm-blooded animals. Any animal species that can maintain a body temperature that is higher than the environment is warm-blooded.

Not all reptiles are cold-blooded. The Argentine black and white tegu is a warm-blooded reptile. Some scientists surmise that some extinct reptiles like avian ones are also warm-blooded.

Alligators are reptiles because:

  • They do not give birth to a young; they lay eggs
  • They do not have mammary glands
  • They are ectothermic; they cannot regulate their body temperature

 During hot weather, alligators must swim to lower their temperature. In the winter, the gators must bask under the sun to get warm.

Related Article: Are Alligators Cold-Blooded or Warm-Blooded?

Similarities between Mammals and Reptiles

Despite their differences, mammals and reptiles also have similarities. For example, both these animals are classes under the phylum Chordata.

Below are some more similarities. Mammals and reptiles came from the same evolutionary ancestors.

  • Both mammals and reptiles have a nerve cord that develops into a brain and spinal column. The nervous system of both animals is sophisticated. However, some animals do not have this
  • As chordates, mammals and reptiles have a central nervous system that governs and manages many areas of perception and movement.
  • Reptiles and mammals are also tetrapods, with the exception of this snake that has no limbs. However, the snake used to be a tetrapod—they used to have limbs, but they evolved for millions of years to make the limbs disappear.

Both animals also have what is called bilateral symmetry. The other type of symmetry is radial. In radial symmetry, the body parts are similar, and they grow around the central axis of the body. Examples of these animals are the sea anemone and the starfish.

In bilateral symmetry, the body is divided into two sides—these are the left and right sides. Alligators, like mammals, have this kind of body. The two sides are like a mirror of each other. However, the internal body organs are not symmetrical.

Related Article: Are There Alligators in Texas?

Are Alligators Amphibians?

No, reptiles and amphibians are not the same. Alligators are reptiles, not amphibians.

Amphibians are small vertebrates that can breathe on land and in the water. Amphibians need water to survive, or at least a moist environment.

The most common example of an amphibian is the frog. Others are toads, salamanders, and the newts. Amphibians can breathe through their skin when in water. Their skin can process oxygen from water, but they do not have gills.

Alligators cannot do this. They cannot breathe underwater, and gators will drown if put underwater long enough. Some experiments conclude that alligators and crocodiles can last up to two hours underwaterbefore they eventually drown.

Some amphibians are also toxic. Their skins have glands that produce poison. One of the worst is the cane toad—even snakes can die if they eat this species of frog.

Will Alligators Evolve into Mammals?

No, they will not evolve as a mammal, and they cannot do it. The modern species of today’s world has already split so far from the point where they could not possibly develop the properties of other species.

Evolution is not linear, and it is not something that an animal wills or commands to happen. For example, there is a point in the evolutionary tree where the two siblings of the same parent exhibited different characteristics.

In this example, one species developed an abnormality, and the other did not. Some siblings do not have the abnormality. The one with abnormality passes this gene to its progeny.

Down the line, both of these will reproduce, and as millions of years go by, they will be so far apart that growing one thing that the previous sibling species did is no longer. In essence, that train has left. 


Alligators are not mammals, and they are not amphibians. They are reptiles. Mammals produce milk and typically give live birth, but reptiles lay eggs. Some reptiles, like some species of snakes, also give birth. As reptiles, alligators are cold-blooded. They depend on the environment to regulate their temperature. If the weather is hot, they need to swim. If it is cold, they need to go and bask under the sun.

Skip to content