What Makes a Mammal a Mammal?

From contributing writer Marci

We always enjoy studying animals. The diversity of nature never ceases to amaze us. Animals come in all sorts of colors, sizes and types. They can all be divided into their own special groups. This week, we studied the group of animals called mammals.

Photo Credit: stuseeger and Animal Photos!

What Makes a Mammal a Mammal?

There are a few main characteristics that set mammals apart from other animal groups, like insects or reptiles. These special characteristics make a mammal a mammal.

  • The animal is warm-blooded or endothermic – able to keep a constant body temperature no matter what the temperature of the environment.
  • The animal has mammary glands, which produces milk to nurse the young.
  • The animal has hair or fur on it’s body, no matter how little.
  • The animal is a vertebrate, or has a backbone.
  • The animal breathes with lungs.

Examples of Interesting Mammals

When you think of mammals, your first thoughts might be of cats, dogs, horses or tigers. (Those are the first animals my kids mentioned.) Those are perfect examples of mammals. They definitely have hair or fur, nurse young, have a backbone and lungs. But, there are other mammals that you might not be so sure about.


One of the most interesting orders of mammals is the monotremes. The duck-billed platypus and the spiny anteater are monotremes. They have fur, backbones, and lungs, but while most mammals give birth to live young, the monotremes lay eggs. However, the monotremes do have mammary glands and nurse their young when they emerge from the eggs. So, they are definitely mammals.


Another order of mammals that get confused with fish are the cetaceans. This group includes whales and dolphins. Even though they look like fish and spend their entire life in water, they have all the necessary criteria to be considered mammals. They are warm blooded, nurse their young, have tiny little hairs on their bodies, have a backbone and have lungs to breathe air through their blowholes.

Learn More About Mammals

There are so many fun ways to study mammals. They are everywhere.

  • Make a mammal list. List all the mammals you can think of. If you are not sure if an animal is a mammal or not, go through the list of mammal characteristics above.
  • Animal flashcards. Sort animals by group – mammals, birds, reptiles, fish, and amphibians.
  • Take a field trip. Go to the zoo or wildlife area and seek out mammals. Make a list.

animal report printable

  • Write a report. Dig deeper and choose a mammal to research and write a report about. You can use this printable.
  • Where can mammals be found? List habitats and what mammals live there and what characteristics they possess that make it possible for them to survive
  • Compare and contrast different mammals. Use Venn diagrams or same/different lists.
  • Sort the stuffed animals. If your house is like ours, you have a zoo full of various types of stuffed animals. Sort out the mammals.

Inspired to study mammals yet? You and your kids will have lots of fun.

More Homeschool Science from Marci

About Marci

Marci is a Christian wife, homeschool mom, science geek, softball coach, ice rink mom and blogger, who needs her morning coffee, hair done and make-up on before attempting of those things. You can find her blogging at The Homeschool Scientist  and at  Overcoming Busy.

This post may contain a link to an affiliate. See my disclosure policy for more information.

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