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Mammal facts for kids

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Mammals
Temporal range: Upper Triassic–Recent
Procyon lotor (Common raccoon).jpg
Raccoon (Procyon lotor )
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Subphylum:
Vertebrata
Infraphylum:
Amniota
Superclass:
Tetrapoda
(unranked):
Synapsida
Class:
Mammalia

Linnaeus, 1758
Subclasses & Infraclasses

Mammals are a group of vertebrate animals. This means they have a backbone. They are part of the class Mammalia. Mammals have fur or hair and can control their body temperature very well. Female mammals give birth to live young. They also produce milk to feed their babies. All mammals take care of their young. This is very important because they usually have only a few babies at a time.

Main characteristics

Myresluger2
The insect-eating giant anteater eats about 30,000 insects every day.
A Bonobo at the San Diego Zoo "fishing" for termites
A bonobo fishing for termites with a stick.
Borneo elephants
Female elephants live in stable groups with their young.
- fighting red kangaroos 2
Red kangaroos "boxing" to show who is stronger.

Reproduction and life cycle

Most marsupial and placental mammals have a special oestrous cycle for reproduction. Females are only ready to mate during a short time each month. This is called being 'on heat'. If an egg is not fertilized, the lining of the uterus is absorbed back into the body. These cycles can happen once or twice a year, or many times. It depends on the type of mammal.

Humans and primates are different. They have a menstrual cycle. Females can be sexually active at any time. However, they can only get pregnant when an egg is released from an ovary. If the egg is not fertilized, the uterus lining is shed. This includes some blood. Eggs are usually released in the middle of the cycle, away from the menstrual period. This ovulation is "hidden." This means it's not obvious when it happens. Scientists think this helps keep males and females together, which is unusual for many other mammals.

Skeleton

One key feature of mammals is their lower jaw. Unlike earlier animals, it has only one bone, called the dentary. This feature helps scientists identify mammals from their fossils. Mammals also have three tiny bones in their inner ear. These are called ear ossicles. A long time ago, these bones were part of the lower jaw in early mammal-like animals.

There are many other special features in a mammal's skull and limbs. Because of this, it is usually possible to identify a mammal just by looking at its skeleton.

Brain and behavior

Another special feature of mammals is the neocortex in their brain. No other vertebrate has this. The neocortex helps mammals have flexible behavior and learn new things. This is very typical of mammals. Animals like reptiles and birds often rely more on "instincts." While almost all animals can learn, mammals learn much more than other vertebrates. Their behavior is much more flexible than, for example, lizards. This is all thanks to their neocortex.

Other parts of mammal life seem connected to this flexibility and learning. Play is like an early learning period. One idea is that through play, mammals develop skills they will need later in life. All young mammals play. This is very clear in more intelligent mammals like primates and cats.

Mammals also show strong emotions, which are quite similar to ours. It is common for humans to form friendly bonds with other mammals. However, it is very hard for a human to have a relationship with a snake or a gecko. This is because reptiles do not have the same basic emotions as humans.

Other unique features

There are about 50 features that are unique to mammals. Here are a few more examples that show how different mammals are from reptiles and birds:

  • They have Sweat glands.
  • Mammals have two sets of teeth in their lifetime. They do not replace teeth continuously. Their teeth have enamel. Reptile teeth are all similar, but mammal teeth follow a pattern: incisors, canines, premolars, and molars.
  • Mammals have two knobs at the base of their skull (occipital condyles). These fit into the top neck vertebra. Most other tetrapods have only one knob.
  • Mammals have separate openings for waste and for reproduction. Reptiles and birds have one common opening called a cloaca.
  • Mammals excrete urea. Reptiles and birds excrete uric acid.
  • Most mammals do not see colors well or at all. Primates are an exception.
  • In reptiles and birds, the main blood vessel carrying oxygen-rich blood from the heart is on the right side of the body. In mammals, it is on the left side.
  • Mammals have specific skeleton features:
    • Their neck always has seven vertebrae, no matter how long it is.
    • Their lower jaw has only one bone on each side, the dentary.
    • Their inner ear has three tiny bones: the malleus, incus, and stapes.

These unique features show that mammals are a distinct group of animals. They all came from a common ancestor.

Main groups

Almost all mammals give birth to live young. There are only two types of mammals that lay eggs. These are called monotremes. They are the duck-billed platypus and the spiny anteater Echidna, which has four species. All monotremes live in Australia and New Guinea. They are the only survivors of an older group of mammals. However, like other mammals, they feed their young with milk and take care of them.

Other mammals are divided into marsupials and placental mammals. Marsupials are mammals with pouches to carry their young in, like the kangaroo. Placental mammals, like humans, develop their young inside the mother's body with a placenta.

Modes of life

Mammals have about 5,488 species. This is not the largest number of species among vertebrates. Birds have about 10,000 species, and reptiles have just as many. Fish have even more species, with about 27,000.

Even so, many zoologists see mammals as a very successful group. One reason is that they live in almost every habitat on Earth. They live in the air, in the water, in forests, in cold places, and especially on grasslands. They are very successful in these areas.

In the air, bats (Chiroptera) are the mammal group with the most species. They are active at night, while most birds are active during the day. Bats are very successful, mostly as nighttime hunters of insects.

Mammals that live in the sea, like whales and pinnipeds, are also very successful. This group includes whales, seals, walrus, and dolphins. They are important predators in the ocean.

There are fewer species of land mammals than lizards. However, there are huge numbers of individual land mammals. They are very important in the life of land biomes. Their ability to move and adapt has made them a very effective group. Many mammals live in cold places. These mammals have thick hair or blubber to stay warm. Others live in rainforests. On land, rodents (like rats and mice) are extremely successful. They are more common in numbers than any other mammals. Large land mammals have been hunted to extinction in some parts of the world. But the ones that remain are now better protected.

Finally, there are the primates. Most primates live in forests. They live in trees, with hands that can grasp, good colour vision, and high intelligence. During the Pliocene period, some primates moved out onto the savannahs as grasslands replaced forests. Mankind developed from this shift to the savannahs.

Taxonomy

Hand milking a cow at Cobbes Farm Museum
Cattle have been kept for milk for thousands of years.
Extinctions Africa Austrailia NAmerica Madagascar
This chart shows the number of large mammal species per continent before and after humans arrived.

Scientists classify animals to show how they are related through evolution. Here is a simplified look at how land vertebrates are grouped:

* Mammalia (give live birth, produce milk, raise their young)

This way of classifying animals helps us understand their history and how they evolved.

Main mammal groups

Most textbooks use a standard way to classify mammals based on living animals. Class Mammalia

  • Subclass Prototheria: These are the monotremes, like platypuses and echidnas. They lay eggs.
  • Subclass Theria: These are mammals that give live birth.
    • Infraclass Metatheria: These are marsupials, like kangaroos, which often carry their young in a pouch.
    • Infraclass Eutheria: These are placental mammals, like humans, where babies develop inside the mother with a placenta.

List of orders

Mammal species pie chart
More than three-quarters of mammal species belong to the orders Rodentia (blue), Chiroptera (red), Soricomorpha (yellow), and Primates (green).

Mammals are divided into many different groups called orders:

Images for kids

See also

Kids robot.svg In Spanish: Mamíferos para niños

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