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Are Chickens Mammals Or Reptiles?

Are Chickens Mammals Or Reptiles?

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There have several debates on whether or not chickens are reptiles or mammals. If you are new to animals, it can be a bit confusing. This is because chickens share some characteristics with both reptiles and mammals.

So are chickens reptiles or mammals? Here is the correct answer: From a technical point of view, chickens are neither reptiles nor mammals. They are birds that can be further classified as fowl. Fowls are birds that are raised for meat and eggs. 

Here are some of the anatomical and physical characteristics of chickens, demonstrating that they are neither mammals nor reptiles.

Chickens Have Feathers While Mammals Have Fur Or Hair

One of the main distinguishing characteristics between mammals and birds is that mammals have fur or hair, while birds have feathers. It is believed that this is because birds and mammals evolved from different animals. 

Mammals evolved from synapsids about 320 million years ago. On the other hand, it is believed that birds evolved from dinosaurs about 140 million years ago. Feathers perform several different functions from those performed by hair in mammals.

Feathers enable birds to fly from one location to another. However, chickens are not the most birds. They have become a little bit heavy over the years because of selective breeding to produce more meat.

Reptiles Have Scales And Not Feathers

Reptiles have scales instead of feathers or hair. This makes them different from birds and mammals. Scales are generally tough and help reptiles to protect themselves from predators. They also give reptiles the ability to be both on land and in water. 

Both Reptiles And Birds Lay Eggs But Mammals Do Not

Some people think that chickens are reptiles because both reptiles and chickens lay eggs. However, this is not the case because there are several differences between how reptiles and chickens lay eggs. 

One of the main differences in the way chickens and reptiles lay their eggs is that egg-laying reptiles carry eggs a little longer than chickens. Reptiles lay their eggs when the embryo is at least one-third developed. After laying eggs, the eggs of reptiles usually hatch after a few days. On the other hand, a chicken’s egg will take less time to be hatched. Typically, it can take about 21 eggs for the chick to develop and hatch once the hen has laid an egg.

Generally, mammals do not lay eggs. According to ScientificAmerican, there are only two egg-laying mammals in the world which are duck-billed platypus and echidna.

Some people will argue that chickens are part of the reptile family since they lay eggs too. However, this is not true because reptiles can not maintain their body temperature. Reptiles will more likely be sluggish if it is cold. Some species of reptiles may hibernate during cold seasons.

A chicken will never hibernate. Interestingly, there are some mammals that do hibernate, adding to the argument of whether chickens are mammals or not. Adding to the confusion is the fact that fish lay eggs.

Reptiles and Chickens Have an Egg Tooth

One of the things that both reptiles and chickens have in common is what is called an egg tooth. Typically, any animal that develops in an eggshell will need a way to get out.

Baby chickens and reptiles that break out of their shells have an egg tooth. Chicks have a hard tooth-like growth on the tip of the beak. These hard growths will fall off shortly after the chicks have broken free from the shells.

On the other hand, mammals do not have an egg tooth because they do not break out of eggs. Once gestation is complete in mammals, the new offspring will travel through the reproductive tract to be delivered. This is unlike chickens where delivery has taken place. 

Mammals and Chickens Are Warm-Blooded While Reptiles Are Not

If you have thought that chickens and reptiles have a lot in common, then you might be wrong. Both mammals and chickens are warm-blooded. On the other hand, reptiles are cold-blooded. 

If you are raising backyard chickens, you will have to ensure that they are warm all the time for them to remain healthy. The regular operating temperature for chickens is about 105 degrees F. This is slightly warmer compared to human beings and much warmer than reptiles. Reptiles are generally much more comfortable with lower temperatures, and most of them operate at about 50-105 degrees F. 

Chickens use their wattles and combs to regulate their body temperature and stay. A chicken’s feathers will also help to keep them warm during cold seasons. On the other hand, mammals use their hair to keep them warm and sweat glands to keep them cool.

Mammals Have Mammary Glands While Chickens Do Not Have

The main characteristic of mammals is that they have mammary glands. This is also the reason why they are referred to as mammals. Mammary glands are milk-producing organs for the sustenance of the young ones of mammals. Female mammals usually have these glands and use them to nurse their young ones. 

On the other hand, neither chickens nor reptiles have mammary glands. Therefore, neither of the two are able to produce milk and nurse their young ones.  

The Beak

It can be assumed that the beak of a bird is the defining feature of the fowl family. Incredibly, both reptiles and mammals share this attribute. Although the shape is not the same, the composition might be the same.

A chicken’s beak is formed by a substance known as keratin which does not stop growing and is good for things that see a lot of wear. In reptiles, a turtle beak contains keratin. On the other hand, mammals have a lot of keratin but not in their mouths. The substance is found in their hooves, human skin, nails, and horns. 

A parrotfish that resembles a parrot has a beak too. Although its beak grows continuously like that of a chicken, it is made of bone instead of keratin.


The bones of a fowl, including chickens, are uniquely hollow. The nature of their bones maximizes strength for weight. Although it was believed that a few reptiles had such bones, their skeletal structure is not the same.

Chickens usually have air sacs sitting within their lightweight frame. The air sacs fill and deflate whenever there is input from the respiratory system. Some of these air sacs are located in bones.

Why Do Some People Think That Chickens Are Mammals?

Some people may think that chickens are mammals because they are found on farms with various livestock such as sheep, horses, cows, pigs, and goats, all of which are mammals. Most people eat chicken meat which is considered healthier than the meat of pigs or cows.

Another reason why some people think that chickens are mammals is that chickens are also kept as pets like cats and dogs. They like to stay in hierarchical groups where hens will prefer to be looked after by their male counterparts. Backyard chickens are devoted and loving parents, just like mammals.

Hens tend to take care of their young ones for several weeks after they have hatched. They will look for places where there is food for the chicks to peck on. On the other hand, mammals too will take care of their young ones from the time they are born until when they are mature enough.

Frequently Asked Questions

Are Chickens Mammals?

The answer is no. Chickens are not mammals. The main features that distinguish chickens from mammals include:

  • They have feathers and not hair or fur
  • They lay eggs
  • Chickens do not have mammary glands

Are Birds Reptiles or Mammals?

Birds are neither reptiles nor mammals. However, they share some characteristics with the two classes. Birds belong to their own order, with chickens classified as fowls. 

There are five classes of animals under the phylum Chordata. They include mammals, birds, reptiles, fish, and amphibians.

What Animal Class Do Chickens Belong?

The scientific classification of a chicken is as follows:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Aves
  • Order: Galliformes
  • Species: Gallus

When Were Chickens First Domesticated?

According to scientists, chickens were first domesticated about 7000 years ago. They were initially domesticated mostly for cockfighting. Later, humans discovered that chickens could be kept as a constant supply of meat and eggs. 

Are Chickens Herbivores, Carnivores, or Omnivorous?

Chickens are generally considered omnivores. You can feed your backyard chickens a wide range of foods such as corn, grass, seeds, small reptiles, worms, and baby mice. 

Are Chickens Dangerous?

Backyard chickens are too small to be dangerous to mature human beings. Besides, people have bred aggression out of most chicken species. However, roosters of most chicken breeds are generally aggressive. They can be very aggressive to other chickens or even small kids.

For How Long Can Chickens Live?

Chickens can live for about five to twelve years. However, the lifespan will mostly depend on the breed of the chicken and their general health condition. 


Chickens are neither mammals nor reptiles. They are birds. However, chickens share several characteristics with both reptiles and mammals.

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