A mammal is an animal that feeds its babies with milk when it is young. There are over 4,500 types of mammals. Many of the most popular animals we know are mammals, for example, dogs, cats, horses, cows, but exotic animals like kangaroos, giraffes, elephants and anteaters belong to this group, too. Humans are also mammals.

Mammals live in all regions and climates. They live on the ground, in trees or underground. Polar bears, reindeer and seals are mammals that live in the Arctic regions. Others, like camels or kangaroos prefer the world’s dry areas. Seals and whales are mammals that swim in the oceans; bats are the only mammals that can fly.

Mammals have five features that make them different from other animals:

  • Female mammals produce milk and feed their babies with it.
  • Only mammals have hair or hair-like skin. All mammals have hair at least some time in their lives.
  • Mammals are warm-blooded. Their body temperature always stays the same and does not change with the outside temperature.
  • Most mammals have a larger and well-developed brain. They are more intelligent than other animals.
  • Mammals protect their babies more than other animals. They prepare them for future life.

People have hunted mammals for ages. They ate their food and made clothes out of their skins. Thousands of years ago wild mammals were domesticated and gave human beings milk, wool and other products. Some mammals, like elephants and camels are still used to transport goods. In poorer countries farmers use cows or oxen, to plough fields.

Today some mammals are hunted illegally. Whales are killed because people want their meat and oil, elephants are killed for the ivory of their tusks.

Mammals are often kept as pets. Among them are cats, dogs, rabbits or guinea pigs.

Mammals are useful to people in many other ways. Some help plants grow and eat harmful insects. Others eat weeds and prevent them from spreading too far. The waste of mammals is used as fertilizers that improve the quality of soil.




Types of mammals

Mammals are divided into three groups:

  1. Monotremes are mammals that lay eggs, like a bird. They live in Australia and New Zealand. The platypus belongs to this group
  2. Marsupials are mammals that raise their young ones in a pouch in their bodies.
  3. Placentals are the largest group of mammals. The babies grow inside their mothers until they are ready to be born. Humans are placentals.


Mammals and their bodies

Skin and hair cover a mammal’s body. Some mammals have horns, claws and hoofs. The hair or fur of a mammal has many functions. The colour often blends in with the world around them and allows them to hide from their enemies. Some mammals produce needles or sharp hair that protects them from attack. But the main function is to keep the body warm.

Mammals have glands that produce substances that the body needs like hormones, sweat and milk.

A mammal’s skeleton is made up of three parts:

  1. The skull contains the brain, teeth and other organs.
  2. The spine or backbone enables mammals to stand or walk.
  3. Limbs are legs and arms of a mammal, often with strong bones.

Mammals have a four-chambered heart system that pumps blood into all parts of their body. The blood brings oxygen to muscles and tissue. The red blood cells of mammals can carry more oxygen than in many other animals. Because mammals have a high body temperature they must burn a lot of food.

Mammals digest food through their digestive system. After food is eaten through the mouth it goes down the throat into the stomach and passes through the intestines. Mammals that eat plants have a complicated system with long intestines that help break down food. Flesh is easier to digest so meat-eating mammals have a simpler stomach.

Mammals breathe air through their lungs. Most of them have noses or snouts with which they take in air. Dolphins and whales breathe through a hole in the top of their back.


Mammals and their senses

Mammals have five senses that tell them what is happening in their surroundings. Not all senses are developed equally among mammals.

Mammals rely on smell to find food and warn them of their enemies. Many species use smell to communicate with each other. Humans, apes and monkeys have a relatively bad sense of smell.

Taste helps mammals identify the food that they eat. Most mammals have a good sense of hearing. Some mammals use their hearing to detect objects in the dark. Bats, for example, use sounds to navigate and detect tiny insects. Dolphins also use such a  system to find their way around.

While higher primates, like humans, apes and monkeys have a highly developed sense of sight other mammals are nearly blind. Most of these mammals, like bats, are active at night.

Mammals have a good sense of touch. They have nerves on all parts of their body that let them feel things. Cats and mice have whiskers with which that they can feel themselves around in the dark.


What mammals eat

Herbivores are mammals that eat plants. They have special teeth that allow them to chew food better. Examples of herbivores are deer, cows and elephants. The giant panda is a plant eater that only eats bamboo.

Carnivores are mammals that eat other animals. Cats, dogs, tigers, lions, wolves belong to this group. They are hunters that tear their prey apart with sharp teeth. They do not chew their food very much.

Omnivores are mammals that eat plants and meat. Bears, , apes, pigs and humans are examples of omnivores.


How mammals move

Most mammals live and move on the ground. They have four legs and walk by lifting one foot at a time or by trotting. Kangaroos hop and use their tail for balancing.

Mammals that live in forests spend a lot of their time in trees. Monkeys can grasp tree branches with claws and can hang on to them with their curved tail. Often mammals spend time hanging upside down in trees.

Dolphins and whales are mammals that live and move around in water. Instead of limbs they have flippers which they use to move forward. Other animals, like the hippopotamus, only spend some time in the water.

Bats are the only flying mammals. Their wings are made of skin stretched over their bones. They can fly by beating their wings up and down.

Gophers and moles are mammals that spend most of their life underground.


How mammals have babies

Mammals reproduce when a male’s sperm gets into contact with a female egg and fertilizes it. A young mammal grows inside the female’s body. Before this can happen mammals mate. Males and females stay together for a certain time.

Unborn mammals live their mother’s body for different periods of time. While hamsters are born after only 16 days, it takes elephants 650 days to give birth. Human pregnancies last about 9 months.
Many new-born mammals, like horses and camels, can walk and run shortly after they are born.

Marsupials give birth to babies that attach themselves to their mothers. They stay in pouches because they are too weak to live alone. Almost all marsupials, including kangaroos, koala bears or wombats live in Australia .

After birth the glands of a female mammals produce milk. Some mammals nurse their babies for only a few weeks. Others, for example elephants, give milk to their babies for a few years.

The duck-billed platypus and echidnas are the only mammals that lay eggs. After the young hatch they drink milk from their mother, just like other mammals do.


Life habits

Many mammals live in families or groups. Wolves and lions help each other in their search for food and protect each other from attackers.
Leopards, cats, tigers and other mammals prefer living alone . They do not share their living space and food that they have, however males and females get together to mate.
Mammals can mark the areas that they live in. They defend these areas by fighting off attackers. Some mammals claim territories only during the breeding season.

Many mammals migrate during special times of the year in order to get food and survive. North American bats travel to the south because insects become scarce during the cold winter months. Zebras and other wild animals follow the rainy seasons in Africa to find green grass. Whales migrate to warmer southern waters off the coast of Mexico to give birth to babies because they could not survive in the cold waters of the Arctic Ocean.

Some mammals hibernate because they cannot find enough food to survive. Their body temperature falls, heartbeat and breathing become slower. During this period hibernating mammals do not eat. They live from the fat of their bodies. Bats, squirrels and other rodents hibernate.

Mammals defend themselves from attackers in many ways. Hoofed mammals can run quickly in order to get food or escape. Squirrels rush into trees to hide. Some animals have special features that protect them from enemies. Skunks spray a bad smelling liquid to keep off attackers. The fur of mammals sometimes changes  with its surroundings. Arctic foxes, for example, are brown in summer and in the winter their coats turn white.


History of mammals

The first mammals probably evolved from reptiles about 200 million years ago during the Mesozoic period. They were rather small in a time when dinosaurs ruled the lands. When the dinosaurs died out about 65 million years ago mammals became the dominant land animals. Many mammals became extinct during the Ice Age , which ended thousands of years ago.

Today, some species are in constant danger of becoming extinct because they are hunted by humans. Hunters and poachers earn money by selling fur, tusks and other parts of mammals. Larger wild animals are often brought to zoos where they are protected.


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Related Topics


  • ages = a very long time
  • anteater = an animal that has a very long nose and eats insects
  • attach = connect
  • attack = violence against someone
  • balance = to keep steady
  • bamboo = tall tropical plant with hollow stems
  • beat = hit, move
  • blend in = to have the same colour as
  • brain = organ inside your head that controls the way you feel, think and move
  • branch = part of a tree that grows out from the main stem; it has leaves and fruits on it
  • breathing = take in air
  • breeding season = time during which animals mate in order to have babies
  • certain = special
  • chew = to bite food many times before you swallow it
  • claim = show that something belongs to them
  • claw = sharp curved nail on an animal
  • coast = where land meets the sea
  • communicate = get into contact with
  • constant = always
  • deer = a large wild animal that can run very fast, eats grass and has horns
  • defend = guard, protect
  • detect = find
  • develop = grow
  • digest = to change food that you have eaten into substances that the body can use
  • digestive system = the way food passes through your body
  • domesticate = to train an animal so that it can work for other people or be a pet
  • dominant = number one
  • duck-billed = with a mouth like a duck
  • echidna = anteater
  • enable = allow, let
  • enemy = person or animal that hates you and wants to fight against you
  • equally = the same
  • escape = to get away from a dangerous situation
  • evolve = grow, develop
  • exotic =  unusual, different
  • extinct = die out
  • feature = quality, characteristic
  • feed = to give food to
  • female =about a woman
  • fertilize = to make a new plant or animal grow
  • fertilizer = substance that is put on the soil to make plants grow
  • flesh = meat
  • flipper = flat part of the body of some sea animals that is used for swimming
  • four chambered = with four separate parts
  • fur = thick soft hair that covers the bodies of animals
  • future = coming
  • gland = organ of the body that produces material that the body needs, like hormones, sweat or milk
  • goods = products
  • gopher = north and Central American animal like  a large rat that lives in holes in the ground
  • grasp = get hold of
  • guinea pig = small furry animal with short ears and no tail; it is often kept as a pet
  • harmful = dangerous
  • hatch = the egg breaks and a young animal comes out
  • hibernate = to sleep the whole winter
  • highly-developed = very good
  • hippopotamus = large grey African animal with a big head and mouth that lives near the water
  • hoof = hard foot of a cow, horse or a camel
  • hop = jump
  • hormone = chemical substance that the body produces and influences how you grow and develop
  • however = but
  • human = a person
  • Ice Age = one of the long periods of time thousands of years ago when ice covered the northern countries
  • identify = recognise, find
  • illegal = against the law
  • including = also
  • instead of = in something’s place
  • intestine = long tube through which food passes after it leaves your stomach
  • ivory = the hard smooth yellow material from the tusks of elephants
  • limb = leg or arm
  • liquid = something watery
  • mark = show the position of something
  • marsupial = animal that carries its baby in pocket of skin
  • mate = to have sex in order to produce babies
  • Mesozoic = the geologic middle ages
  • migrate = to travel regularly to another place in the world
  • mole = small dark furry animal that is almost blind ; moles usually live under the ground
  • navigate = travel around, steer
  • nurse = feed with milk
  • oxygen = gas that has no colour or smell and which we need to breathe
  • platypus = a small furry animal that has a mouth and feet like a duck
  • plough =  turn over the earth so that seeds can be planted
  • poacher = someone who catches or shoots animals illegally
  • popular = well-known
  • pouch = pocket of skin
  • prefer = like
  • pregnancy = when a female has a baby growing inside her
  • prepare = to get ready
  • prey = victim, target, the animal they want to eat
  • primate = a member of a group of animals that include humans and monkey
  • protect = defend against enemies
  • raise = bring up
  • rather = relatively, quite
  • reindeer= a large deer with long horns that lives in northern, colder areas
  • rely = depend on, need
  • reproduce = to have babies
  • reptile = animal like a snake or lizard whose body temperature changes according to the temperature around it
  • rodent = small animal that has long sharp front teeth , like a rat
  • rule = to have the power over others
  • rush = hurry
  • scarce = rare, nor enough
  • seal = a large sea animal that eats fish and lives around the coast
  • search = look for
  • sense = one of the five natural powers : seeing, hearing, feeling, tasting, smelling
  • sense of hearing = the way an animal can hear
  • share = use with another animal
  • sight = vision, ability to see
  • skull = bones of a person’s or animal’s head
  • skunk = a black and white North American animal that produces a strong bad smell when it is attacked
  • snout = long nose of an animal
  • soil = the top layer of the earth, on which plants grow
  • species = group of plants or animals that are alike and can produce young ones
  • sperm = a cell of a man that can produce new life
  • spine = the row of bones down the centre of your back
  • spray = a stream of very small drops
  • spread  = to move from one place to another
  • squirrel  = small animal with furry skin that climbs trees and eats nuts
  • stretch = to go from one place to another
  • surroundings = the world around us
  • survive = continue to live
  • sweat = drops of salty liquid come through your skin because it is hot or you are doing a lot of exercise
  • tail = part that sticks out of the back of an animal
  • tear = rip
  • territory = land
  • throat = the passage from your mouth to the tubes that go to your stomach
  • tiny = very small
  • tissue = the material that forms cells
  • trot = to move quickly with each front leg moving at the same time as one of the back legs
  • tusk = long curved tooth of an elephant
  • upside down = with the top at the bottom and the bottom at the top
  • warm-blooded = animals that have the same body temperature all the time
  • waste = the material that animals leave after they digest food
  • weak = not strong
  • weed = wild plant that prevents crops or garden flowers from growing in the right way
  • well-developed = something that works very well
  • whale = very large mammal that swims in the sea
  • whisker = long hair that grows near the mouth of a cat or mouse
  • wombat =an Australian animal  like a small bear whose babies live in a pocket of skin