Updated: October 6, 2022
© GoodFocused/
Share on:


The official mammal class is Mammalia. Types of animals that are mammals include warm-blooded vertebrates that have hair or fur and whose babies drink milk. Unlike other animal types like birds and insects, all mammal babies drink milk that comes from their mother’s bodies. This is one of the key ways to know if an animal is a mammal. 

What Are Mammals? – The 10 Characteristics You Need to Know

Mammals have many other unique characteristics compared to other animal types. You can use some of these key mammal markers to identify whether an animal is a mammal:

  1. Warm-blooded vertebrates – Mammals are endothermic, meaning they have a constant body temperature. Mammals are also vertebrates, meaning they have a backbone
  2. Red Blood Cells Without Nucleus – Mammals have adult (mature) red blood cells, known as erythrocytes, that lack a nucleus. This is unique compared to other vertebrates. 
  3. Has hair or fur – Mammals commonly have hair, or fur. Though hair and fur are chemically similar and both made of keratin, they are characteristically different. Hair is normally longer and thinner than fur, while fur is usually shorter and coarser. Both serve as insulators for animals. 
  4. Contains a Malleus, Incus, and stapes – The Malleus is a small bone in the middle ear that is shaped like a hammer. It connects the inner surface of the eardrum with the incus. Given it’s shape, the name is derived from the Latin word for ‘mallet’. The incus is shaped like an anvil and serves a similar function, vibrating to transmit sound. The stapes is a stirrup shaped bone. Together they form the ‘hammer, anvil, and stirrup’, three of the smallest bones in the human body. The stapes is the actual smallest. 
  5. Able to produce milk Mammals contain mammary glands. These glands give them the ability to produce milk to feed their offspring.
  6. A diaphragm – Mammals have a diaphragm sitting between their heart and lungs 
  7. Hinged Lower Jaw Connected To Skull – Mammals have a hinged lower jaw that connects directly to the skull. By comparison, all over vertebrates connect through another bone known as the quadrate. This mammal articulation allows them to more easily grasp and chew food, as well as chew sideways. 
  8. Left aortic arch – In mammals, the fourth (left) pharyngeal artery is most commonly the arch of the aorta. This differs compared to other animal types. There can be rare cases where mammals have a right aortic arch variant. 
  9. Neocortex – Mammals commonly have a neocortex in their brain. This specialized region allows them to both hear and see.
  10. Live Birth – Mammals are viviparous, meaning they give birth to live babies. There are three different types of mammal birth. Monotremes, marsupial, and placental mammals, discussed further below. 

Mammal Exceptions

There are some exceptions to the mammal criteria. Whales are mammals but they are born without hair or fur as it has typically gone after the fetal stage. Yes, that means the blue whale is in fact a mammal!

Monotremes like the duck-billed platypus and echidnas are a whole category of egg-laying mammals that are the only mammals which do NOT give birth to live young. Instead, animals like the platypus and echidnas actually lay eggs.

The Three Different Types of Mammal Births


A rare and unusual category of mammal birth where the animal lays eggs. There are only five known monotremes mammals on the planet, with the platypus and echidna’s being the most well known.


Marsupial mammals give birth to their young before they are fully developed. The babies then complete their growth outside of the mother but in a ‘pouch’. Well-known marsupial examples include kangaroos, opossums, and wombats. 

Placental Mammals

Members of this birth group have a birth procedure containing a placenta. The presence of a placenta transfers important nutrients between the mother and offspring, helping protect the young and ensure a well-developed birth. Placental births are the most common among all mammals with examples including dogs, horses, cats, and humans. 

Which Types of Animals Are Mammals?

These are some examples of different types of Mammals!

A Zuchon

The breed often changes colors throughout its life, with its puppy coat becoming lighter over the first few years of life, then darkening as he ages.

A Zorse

The offspring of a Zebra and Horse parents!

A Zonkey

The offspring of Zebra and Donkey parents!

A Zokor

Zokors are expert diggers. They burrow tunnels hundreds of feet long!

A Zebu

There are around 75 different species!

A Zebra

Stripe patterns are unique to each individual!

A Yorkshire Terrier
Yorkshire Terrier

Highly energetic and eager for adventure!

A Yorkiepoo

The Yorkie-Poo originated from the hybrid poodle phase of the late 20th century

A Yorkie Bichon
Yorkie Bichon

Yorkie Bichons can come in a wide range of colors including black, white, blonde, gray, golden, or dark brown.

A Yoranian

These dogs are very intelligent and are great with children.

A Yakutian Laika
Yakutian Laika

The Yakute people were likely the first to use dogs to pull sleds, so the Yakutian Laika was probably among the first sled dogs.

A Yak

Yaks can live at altitudes up to 20,000 feet--the highest of any land-dwelling mammal.

A Xoloitzcuintli

The Xoloitzcuintli is the national dog of Mexico

A Xerus

Squirrel that lives in burrows in Africa.

A Woolly Rhinoceros
Woolly Rhinoceros

The woolly rhinoceros roamed the earth between three and a half million and 14,000 years ago.

A Woolly Monkey
Woolly Monkey

Has a long, strong prehensile tail!

A Woodrat

Pack rats love shiny objects and will steal your jewelry.

A Wood Bison
Wood Bison

The reintroduction of wood bison into Alaska is considered one of the world’s best conservation success stories.

A Wombat

Spends most of the day underground!

A Wolverine

Releases a strong smelling musk in defence!

A Wolf

Thought to date back more than 300,000 years!

A Wirehaired Pointing Griffon
Wirehaired Pointing Griffon

A Wirehaired Pointing Griffon’s coat makes it look like it has a mustache and beard!

A Wire Fox Terrier
Wire Fox Terrier

The Wire Fox Terrier was bred from the now extinct Rough Coated Black and Tan Terrier to hunt down foxes.

A Wildebeest

Can trek more than 1,000 miles every year!

A Wild Boar
Wild Boar

Males have a top tusk to sharpen the bottom one!

A Whoodle

Whoodles are good swimmers

A Whitetail Deer
Whitetail Deer

Although deer are herbivores, they will sometimes eat mice and birds when they can catch them.

A White-tail deer
White-tail deer

White-tail deer are good swimmers

A White-Faced Capuchin
White-Faced Capuchin

One of the world's most intelligent monkeys!

A White Tiger
White Tiger

None have been seen in the wild for 50 years!

Is it a Mammal? Your Questions Answered

From rodents to whales and everything in between, it’s not always easy to tell which animals are mammals and which animals fall under another category such as fish, reptiles, or amphibians. If you’ve ever questioned whether or not one of these animals is a mammal, this is the list for you! Read on to find out more about which species are considered mammals and what makes them qualify as such.

  • Are Sharks Mammals? Some shark species give live birth, but are they mammals since, unlike typical fish, their skeleton is made of cartilage? Find out more!
  • Are Bats Mammals? It’s somewhat baffling — bats are capable of flight, so does that make them birds or mammals?
  • Are Birds Mammals? Some birds, such as the kiwi, are flightless. Does that mean birds are classified as mammals? We’ve done the search.
  • Are Humans Mammals? It may sound like a silly question, but are humans animals or mammals? And if we’re mammals, how do we differ from other mammalian creatures?
  • Are Marsupials Mammals? There are over 250 species that are classified as marsupials. But are they mammals?
  • Are Penguins Mammals? Penguins can swim under water and traverse the land, but they lay eggs. Do they qualify as mammals?
  • Are Fish Mammals? There are some species of fish that can breathe air, but are they considered mammals?
  • Are Chickens Mammals? Chickens have feathers, beaks, a four-chambered heart, and they lay eggs. Does that make them a mammal or a bird?
  • Are Rodents Mammals? Rodents have hair, tails, teeth, and they give live birth — is that enough to make them mammals?
  • Are Dogs Mammals? Have you ever wondered whether or not man’s best friend is a mammal? Read on to find out!
  • Are Platypuses Mammals? Platypuses lay eggs while mammals do not. They are also semi-aquatic. But is it possible that platypuses are still mammals?
  • Are Seals Mammals? There are over 30 species of seals, and they live all over the world. They have fur, they’re semiaquatic, and they happen to have flippers. So, are they mammals or not?
  • Are Elephants Mammals? Elephants are warm-blooded vertebrates that nurse their young, but they aren’t covered in fur like most mammals. Or are they?
  • Are Turtles Mammals? Is a turtle a mammal or a reptile? Turtles breathe air and don’t lay their eggs underwater. Find out more!
  • Are Cats Mammals? How many mammalian traits do cats have? Is it enough to classify them as mammals?
  • Are Armadillos Mammals? An armadillo certainly looks reptilian, with its hairless body. But is it a reptile or a mammal?
  • Are Owls Mammals? Owls hunt small animals, but are they considered to be one themselves?
  • Are Coconuts Mammals? Coconuts share some interesting characteristics with mammals, including the fact that they possess hair and milk. Read on to find out more about their similarities and differences.
  • Are Snakes Mammals? Some snakes give birth to live young, yet they’re cold-blooded. Does this make snakes a mammal or a reptile?

List of Mammals

Mammals by Letter Lists

Jump to a filtered list of Mammals that start with a specific letter!

Share on:

FAQs (Frequently Asked Questions) 

What is considered a mammal?

Mammals are those animals that have some of the 10 characteristics listed above. The most notable mammal characteristics include having hair or fur, having live births, and feeding their young milk.

What animals are Mammals?

There are nearly 6,500 publicly recognized mammal species with more being discovered all the time. Popular mammal examples include cats, dogs, horses, elephants, whales, and humans.

Are whales mammals?

Yes! Whales are marine mammals. Surprisingly, they even exhibit one of the hallmark traits of mammals and even have hair. Though, whales mostly have hair in the womb and it is mostly gone at or slightly after birth.

What is the largest mammal on earth?

The largest mammal on earth is the blue whale. At over 100ft in length and 350,000lbs blue whales are also the largest animal alive on earth today, as well as the largest animal that has ever lived!

What did mammals evolve from?

Mammals are believed to have evolved from reptiles during the triassic period (approximately 200 – 250 million years ago), specifically of the order Therapsida.

What is the smallest mammal?

At approximately 1.6 inches long and less than 1 ounce the smallest known mammal on earth today is the Etruscan Shrew.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.