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Check out more on a-z-animals YouTube Channel.

The art of cool. Who doesn't want to think they have a firm grasp of what it takes to be cool? We like to practice and hope to perfect the skill. Our wardrobe, the walk, the dance, our Top Gun shades. Many of us aim - struggle - to project cool. But the best cool has a natural flow. It's showing up and being ourselves, being a slice of mellow you can't generate artificially.

This is why you gotta love cool animals! While there are animals that indeed try to get your attention (we're talking to you, dog world) but overall, animals are just going about their business as they project an aura of cool that you want to wear.

These are the 10 coolest animals in the world:

#10. Okapi

The Okapi has a very long tongue. Their tongues are so long, in fact, that okapis use them to wash their eyelids, clean out their ears, and even swat insects away from their neck.
seth miles/Shutterstock.com

You might think this creature is a relative to the zebra with its striping. But they are cousins of the giraffe. Herbivores, the okapi mostly diets on grass, leaves, and other plants. You'll find them in Africa's Democratic Republic of Congo.

Among the okapi's predators are leopards and humans. The okapi does have these cool natural defenses. Their large ears can detect the slightest disturbance in the environment, warning them of danger. But - wait for it! - all the animals have to do is turn away as the brown and white markings on their butts make for great camouflage in the forest.

#9. The Fossa

Found in the forest habitats of Madagascar, the fossa has the physical characteristics of a hairless cat. These carnivores are more Mongoose than feline though. They hunt day and night with more than half their feed consisting of lemurs.

Despite its cat-like appearance, the animal can grow up to six feet in length. Fossas are fierce predators with semi-retractable claws. Unlike many animals in trees who usually jump down, the fossa can climb down headfirst, which can be jarring to see. And young females are temporarily guys until they achieve adulthood.

#8. The Maned Wolf

This lanky critter is more dog than anything and has no relation to either fox or wolf. It calls home the grasslands of central-west, south, and southeastern Brazil. The maned wolf's a loner and splits it dining between plants and meats.

The maned wolf uses horrible smelling feces and urine to mark its territory. And it works. Not many animals or humans will stay in the vicinity long. Surprisingly, this wolf doesn't howl, another trait that separates it from the family. Instead, similar to dogs, the creature emits loud or roaring barks. They use the sounds to scare other wolves and to let mates know where they are. Ain't that cute?

#7. The "Blue Dragon"

Blue Dragon, Glaucus atlanticus, eat large, venomous prey, such as the Portuguese man o' war and the blue button jelly, and store their prey's stinging cells in their bodies to later use against predators.

Its formal name is Glaucus atlanticus. It floats upside down in the water, using its blue side to blend unseen into the water. If you spy it, you see what looks like a small dragon. Hence, the "Blue Dragon" moniker. These cool animals feed on the infamous man o' war, a species it's actually related to. The Blue Dragon also delivers an effective sting you want nothing to do with.

Considered a sea slug, the blue dragon is a relatively new find. But unlike a lot of new species that habitat select regions, this species is popping up in what seems everywhere. Initially calling the Indian Pacific Oceans their home, researchers had to revise their findings after the animals showed in the Bay of California. Next, the critters showed up in Taiwan. Later, they, apparently ready to take over the world, showed up in South Padre Island in Texas and, the same year, South Africa 's Cape Town.

#6. Japanese Spider Crab

This arachnid makes the cool list for its ability to scare the heck out of you. If you fear spiders, stay out of the waters surrounding Japan. This spider crab, from claw to claw, has been sighted in sizes of up to 18 feet. The only sea creature heavier than the Japanese spider crab is the American lobster. The Japanese spider crab's a delicacy in its region but not easy to catch.

These creatures have extremely long legs, adding to the creepy. At their largest, they stand at least two to three feet (or more) off the ground. And their legs never stop growing throughout their lifespan! Fortunately, they tend to keep to shallow, colder water. Oddly enough, they don't swim!

#5. Slow Loris

If a slow loris gives you the eye, your heart will melt. Just melt like butter. And while you embrace its adorability, it may take the opportunity to share a bite that'll be seriously venomous. They're also capable of being completely silent to prevent discovery.

The slow loris has two - that's dos - tongues. The jagged tongue's in play for cleaning teeth. The longer one sucks at flowers to get nectar. These cool animals are the only primates with a venomous bite. But usually, it's only applied to protect themselves from predators and rivals.

#4. Angora Rabbit

The hairiest breed of rabbit, the angora is famous for being one of the most touchable creatures in the world. Fluffy and cute, they originate in Turkey but spread across Europe before import to these United States. The angora rabbit sheds its fur at least three or four times a year. As angora is a highly sought-after fabric, we wonder if owners wait around with brooms.

Angora is as much as seven times comfier and warmer than sheep wool. Unfortunately, that's a challenge for owners who have to manage high temps around angora rabbits. They're pretty hardy but do thrive better in winters. Some suggest you keep the rabbit trimmed during heated seasons. And why not? Make a sweater.

#3. Pacu Fish

Catch a pacu, open its mouth and guess what you'll see? A mouth full of what looks like human teeth and a tongue. A member of the piranha family, it's a larger sea creature and resides in South American waters and in the rivers of the Amazon. The pacu does not chow on meat though. It prefers nuts and seeds, though they have the capacity to injure other animals.

Owners of the pacu fish find they have a laid-back temperament. Like a canine, the fish has the capacity to nuzzle comfortably with its owner. (How a fish nuzzles is beyond us and we haven't found any video to confirm this.) Still, we'd imagine it'd be pretty cool to have a fish the size of a small child sitting in your lap while you read James Joyce.

#2. Axolotl

An Axolotl in an aquarium. The axolotl is a freshwater salamander that spends its entire life underwater. This highly intelligent amphibian's behavior can range among individuals from social to solitary and active to dormant.
Spok83/Shutterstock.com

The axolotl could be a Pokémon or even the new character in a Pixar hit. It can even look like it's smiling at you. Spotted in lakes around Mexico, the salamander is amphibious but strictly lives its adult life in the water. Unfortunately, they're an endangered species, falling prey to predators and the urbanization of their ecosystems.

What's extremely cool about these animals is their ability to regenerate. Well, it's not unusual for many species of amphibians, but axolotls go into territory no amphibian has. They too regenerate limbs but also spines, jaws, and even parts of the brain with no sign of scarring. Science has studied the creatures for years trying to figure out how they do it.

#1. Blobfish

The female Blobfish lays thousands of small pink eggs on the seafloor. Either the female or male blobfish will sit on the eggs to protect them from predators.

At first study, the blobfish looks like melted wax, the face resembling a grouchy old man. It has dark eyes on opposite sides of its face, a big punchdrunk nose, and the countenance of constipation. Living in the deepest waters of Tasmania, Australia, and New Zealand, the blobfish's density is barely above that of water. They hunt by floating lazily until creatures wander into its mouth. Now, that's either cool or really lazy.

They have strong familial instincts. The female can lay thousands of eggs and either parent will sit on the hatchlings to protect them from predators. Unlike other fish, blobfish don't have a swim bladder. They carry an air sac that lets them adjust their buoyancy. And, for the record, the blobfish only has that melted look out of water.

In order, the coolest animals in the world are:

Okapi

The Fossa

The Maned Wolf

The 'Blue Dragon'

Japanese Spider Crab

Slow Loris

Angora Rabbit

Pacu Fish

Axolotl

Blobfish

BONUS Coolest Animals!!! - Tigers

Young Siberian tiger, Panthera tigris altaica, walking in a forest stream in a dark green spruce forest. Tigers are very good swimmers and have been known to drown their prey.
Martin Mecnarowski/Shutterstock.com

So many of the animals on the list are unique and exotic. We thought this won't be a well-rounded piece if we didn't include at least one familiar creature that didn't feel like we made it up.

The tiger, with its majestic stance, has always been a cool animal. It reeks of elegance and leadership. The largest of all cats, it calls home to Turkey, Asia, Russia, and many other parts of the world. They are fierce and powerful creatures. And those stripes!

You can hear the tiger's roar up to two miles away. Their vocal stretch would make opera divas stomp off in a jealous funk. And while you don't want to cuddle with them, they have a lot in common with the house cat. They play, rest much of the day and get a kick out of catnip. But unlike most felines, the tiger loves water and is known to swim up to five miles a stretch.

Next Up: 10 Most Beautiful Animals in the World

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The art of cool. Who doesn't want to think they have a firm grasp of what it takes to be cool? We like to practice and hope to perfect the skill. Our wardrobe, the walk, the dance, our Top Gun shades. Many of us aim - struggle - to project cool.

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This is where you'll discover fun (and furry!) animal facts about our planet's incredible wildlife. From majestic mammals and soaring birds to super sea creatures and curious creepy crawlies - it's an animal lover's dream!

Discover rare and unusual species, brilliant bears, fierce felines, awesome reptiles and incredible marine life, just to name a few.

Learn animal facts about habitat, behaviour, speed and appetite (beware, the great white shark!) and most importantly, discover the threats that many of these amazing animals face today.

Ready for an adventure, gang? Click about to get started!

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The golf-ball sized blue-ringed octopus has enough poison to kill 26 humans in a matter of minutes.

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The 9 Most Interesting Animals in the World

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The 9 Most Interesting Animals in the World

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Did you know we share our planet with over 1 million species of insects? That's a lot of bugs! Scientists are discovering more insects every day. Insects are also called arthropods. Some have wings, and some don't. But all have a few things in common.

Fun Facts about Insects for Kids

Insects don't have bones or a backbone like us. They're called invertebrates. That means they have a hard exoskeleton, or shell, on the outside of their bodies that protects them.

All insects have three parts: the head, the thorax, which is the middle part, and the abdomen, or end part.

Insects have two antennae. They also have six legs.

Spiders are not insects. Spiders have eight legs. They are related to scorpions and belong to the arachnid family.

All insects hatch from eggs. The babies are called larva.

All insects go through the same life cycle. Life begins as an egg. The egg hatches and larva emerge. Larvae usually look nothing like the adult insect. The larvae enter a pupa, chrysalis or cocoon. An adult insect emerges from the pupa.

Insect Vocabulary

Learn More All About Insects

Check out this awesome video about how insects in the animal kingdom interconnect:

A video documentary all about insects and their lives.

Insect Q&A

Question: How many insects live on the planet?

Answer: Insects make up over 90 percent of the animal life living on earth.
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Question: What's an Anthropod?

Answer: Actually there's no Anthropod insect. Anthropoids are actually something that is similar to the shape of a man, like a chimp. Some various extinct kangaroo species were called Anthropoids, as are also some non-living things such as machines or artworks.
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Question: What is an Arthropod?

Answer: Arthropods are invertebrate animals with segmented bodies, jointed limbs (legs) and cuticles. Spiders, insects, crabs and so forth are all arthropods. Their rigid cuticle inhibits growth, so arthropods replace it periodically by moulting.
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Question: How large is an Arthropod?

Answer: Arthropods range in size - from microscopic plankton up to a few meters long.
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Question: How many insects are Arthropoids?

Answer: Actually, all insects arthropods but not all arthropods are insects...
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Question: Are insects helpful?

Answer: Some insects, such as bees, help humans by pollinating crops. Others, like mosquitoes or fruit flies, can carry disease or damage crops.

Enjoyed the Easy Science for Kids Website all about Insects info? Take the FREE & fun all about Insects quiz and download FREE all about Insects worksheet for kids. For lengthy info click here.

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Did you know we share our planet with over 1 million species of insects? That's a lot of bugs! Scientists are discovering more insects every day. Insects are also called arthropods. Some have wings, and some don't. But all have a few things in common. Insects don't have bones or a backbone like us.

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And it seems we're not the only ones - wildlife presenter Chris Packham chatted to us about all things bugs...

"When I was a child, at the front gate of my parents' house was a bush which was the home to the most beautiful ladybirds. I would stand on the wall and catch ladybirds of all different colours," he says.

"My favourite bug is the Hornet." Chris tells us. "They're fantastic insect predators. Watch them hunting, they are like aerial tigers. Equally they are very beautiful with their patterning and colouring."

"It's really important for kids to explore the bug life in their garden because it's been proven that being connected to nature makes you happier."

Shockingly, new research from intu Shopping Centres found that one in six kids hasn't seen a bug in six months!
Yikes! Come on gang, we're going to find out what makes insects so amazing, in our 25 cool facts about bugs!
Facts about bugs

1) A ladybird might eat more than 5,000 insects in its lifetime!

2) Fruit flies were the first living creatures to be sent into space.

3) Dragonflies have been on earth for 300 million years!

4) A bee's wings beat 190 times a second, that's 11,400 times a minute.

5) The stag beetle is the largest species of insect to be found in the UK.

6) Caterpillars have 12 eyes!

7) One dung beetle can drag 1,141 times its weight - that's like a human pulling six double-decker buses!

8) A single honeybee colony can produce around 100kg of honey each year - that's 220 jars!

9) An ant-eating assassin bug piles its victims onto its body to scare predators.

10) Large groups of fireflies sometimes flash in unison.

11) To breathe underwater, the water scorpion uses a snorkel-like tube on its abdomen.

Did you know that we have a FREE downloadable 'Make a bug hotel' primary resource? Great for teachers, homeschoolers and parents alike!

12) There are 36 species of dragonfly found in the UK.

13) Bulldog ants can leap seven times the length of their bodies!

14) Mosquitos are attracted to smelly feet!

15) Some male stoneflies do push-ups to attract a mate.

16) Butterflies taste with their feet.

17) Grasshoppers have special organs in their hind legs that store energy for jumping.

18) A hornet's favourite food is a... bee!

19) The red postman butterfly develops its own poison by eating toxic plants!

20) A sea skater's leg hair traps air, enabling it to float on water.

21) Grasshoppers existed before dinosaurs!

22) A ladybird might eat more than 5,000 insects in its lifetime

23) Damselflies have been on earth for more than 300 million years

24) Greater water boatmen breathe through their bottom!

25) Male giraffe weevils use their long necks to fight each other.

Photos: Getty Images UK.

Look for bugs in the garden!

There are lots of exciting things you can find if you go on a bug safari in your garden!

"You can find everything from ladybirds, bees and beetles, such as the stag beetle," says Chris Packham.

"What's also great about your insects in your backyard is that there are seasonal changes and you can always find something new."

Wow! If you want to go exploring in your garden, you can use our insect safari primary resource to help you!

What do you think to these cool facts about bugs? Let us know by leaving a comment, below!

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25 cool facts about bugs! | National Geographic Kids

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And it seems we're not the only ones - wildlife presenter Chris Packham chatted to us about all things bugs... "When I was a child, at the front gate of my parents' house was a bush which was the home to the most beautiful ladybirds.

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They are warm-blooded and lay eggs. Their bodies are covered with feathers and they have wings. Feathers have three functions: flight, temperature regulation and display. Most birds have hollow main bones with air sacs in them. This makes them lighter and makes flight easier.

Birds are bipedal: they have two legs which are often covered with scales (small, flat plates which over-lap in the same way as feathers). They have a hard beak with no teeth.

Because birds keep a high body temperature, they use lots of energy. So, they need to eat a lot of food compared with their weight.

More than 9000 different species of birds are known.

Birds are found on every continent of the world. Birds of different types can live in freezing cold environments, and others can live in hot deserts. Birds live in forests, in grasslands, on cliff faces, in river banks, on stony sea shores, down mine shafts and in the roofs of houses.

Different types of birds eat different foods. Most birds are carnivorous meaning that they eat flesh, at least some of the time. Many birds live on insects or on fish. Some eat small reptiles and mice. Birds of prey eat mammals and other birds. Some birds are scavengers and eat the bodies of creatures that have died. Many birds such as parrots and finches live on seeds and fruit. Some birds that eat mainly seeds feed their young on insects. A few types of birds eat green plants, but only one species lives on leaves (the hoatzin). Hummingbirds and honeyeaters live on the nectar or honey in flowers.

All this applies to living birds. Birds are the descendants of theropod dinosaurs, and the early birds looked much like small carnivorous dinosaurs. Much is now known about the origin of birds. From fossils we know that these dinosaurs had feathers, and early birds had teeth.

Because birds live on every continent and have adapted to all sorts of conditions, different types of birds look very different from each other. The most noticeable differences are the size, the shape of the beak, the length of the legs, the length of the neck and the colour.

The smallest types of birds are tiny birds that feed on nectar, honey and insects. The biggest birds are flightless birds with long legs - ostriches, emus and cassowaries. However, very large birds are also found soaring high in the sky - eagles, vultures, albatross and pelicans. One way to understand the living habits of a bird is to look at its legs and feet, its beak, its neck and its wings.

Birds that are shaped like torpedoes are good at diving. Albatross, seagulls and kingfishers all have long strong beaks for catching fish. Some birds, such as eagles, owls vultures and hawks, have beaks which are hooked and very large claws (also called "talons") with which they can tear and carry meat.

Some birds have very long thin beaks that they use for dipping into flowers or poking into holes in the ground. These include hummingbirds, bee eaters and avocets. Some birds have short beaks but wide mouths that are perfect for catching insects in the air, like swallows, swifts and nightjars. Some birds that eat fruit, like toucans and hornbills, have beaks which are enormous, but are very light in weight. The curved beaks of parrots are good for eating large seeds and cracking nuts, while birds that peck small seeds and food from the ground have short beaks like pigeons.

Bird colours

Birds come in a huge range of colours. These colours can be useful to a bird in two ways. Camouflage colours help to hide the bird, and bright colours identify the bird to others of the same species. Often the male is brightly coloured while the female is camouflaged.

Bird camouflage

Many birds are brown, green or grey. These colours make a bird harder to see; they camouflage the bird. Brown is the most common colour. Brown birds include sparrows, emus, thrushes, larks, eagles, falcons and the female birds of many species such as wrens, ducks, blackbirds and peacocks. When a brown bird is in long grass or among tree trunks or rocks, it is camouflaged. Birds that live in long grass often have brown feathers streaked with black which looks like shadows. A bittern is almost invisible in long reeds. Other birds, including starlings and minahs, are quite dark in colour, but are flecked with little spots that look like raindrops on leaves.

Many birds from hot countries are green or have some green feathers, particularly parrots. Birds that live in green trees often have green backs, even if they have bright-coloured breasts. From the back, the birds are camouflaged. This is very useful when sitting on a nest. The bird's bright-coloured breast is hidden. Budgerigars are bred in different colours such as blue, white and mauve, but in the wild, they are nearly all green and yellow. Even though they fly very well, they normally spend a lot of time on the ground, eating grass seeds. Their yellow and black striped back helps to hide them in the shadows made by long dry grass, while their green breasts are a similar colour to the leaves of gum trees.

Black birds include crows, ravens and male blackbirds. Some birds that are dark colours spend quite a lot of time on the ground, hopping around in the shadows under bushes. Among these birds are the male blackbird and the Satin Bowerbird which is not black but very dark blue. Crows and ravens often perch high on bare trees in the winter, where their black shape against the sky looks like the dark bare branches.

Noticeable colours

Many birds are not camouflaged, but stand out with vivid colours. They are usually male birds whose females are dull and camouflaged. The function of the colours is two-fold. First, the colours help them get mates, and second, the colours identify them to other males of the same species. Many birds are territorial, especially in the nesting season. They give out territory sounds and are easily seen. This lets other males know they will defend their territory. It sends out a "look elsewhere" signal to their competitors.

Many other birds are very brightly coloured, in countless combinations. Some of the most colourful birds are quite common, like pheasants, peacocks, domestic fowl and parrots. Colourful small birds include blue tits, the gold finches, humming birds, fairy wrens and bee eaters (which are also called rainbow birds). Some birds, like those of the bird of paradise in Papua New Guinea have such beautiful feathers that they have been hunted for them.

The peafowl is the best example of a display of colour to attract a mate. Also the male domestic fowl and junglefowl have long shiny feathers above his tail and also long neck feathers that may be a different colour to his wings and body. There are only a very few types of birds (like the eclectus parrot) where the female is more colourful than the male.

'Pied birds' are black and white. Black and white birds include magpies, pied geese, pelicans, and Australian magpies (which are not really magpies at all). Pied birds often have brightly coloured beaks and legs of yellow or red. The silver pheasant, with its long white tail striped with fine bars of black, has a brightly coloured face.

Most birds can fly. They do this by pushing through the air with their wings. The curved surfaces of the wings cause air currents (wind) which lift the bird. Flapping keeps the air current moving to create lift and also moves the bird forward.

Some birds can glide on air currents without flapping. Many birds use this method when they are about to land. Some birds can also hover and remain in one place. This method is used by birds of prey such as falcons that are looking for something to eat. Seagulls are also good at hovering, particularly if there is a strong breeze. The most expert hovering birds are tiny hummingbirds which can beat their wings both backwards and forwards and can stay quite still in the air while they dip their long beaks into flowers to feed on the sweet nectar.

Types of flight

Different types of birds have different needs. Their wings are adapted to suit the way they fly.

Large birds of prey, such as eagles, that spend a lot of time soaring on the wind have wings that are large and broad. The main flight feathers are long and wide. They help the eagle to stay on rising air currents without using much energy, while the eagle looks at the ground below, to find the next meal. When the eagle sees some small creature move, it can close its wings and fall from the sky like a missile, opening its great wings again to slow down as it comes to land. The world's largest eagle, the Philippine eagle has a wingspan of about 2 metres (6.7 ft) wide.

Birds that live in grassland areas or open forests and feed on fruit, insects and reptiles often spend a lot of time flying short journeys looking for food and water. They have wings that are shaped in a similar way to eagles, but rounder and not as good for soaring. These include many Australian birds like cockatoos.

Birds, such as geese, that migrate from one country to another fly very long distances. Their wings are big and strong, because the birds are large and they stock up on food for the long flight. Migrating water birds usually form family groups of 12-30 birds. They fly very high, making use of long streams of air that blow from north to south in different seasons. They are very well organised, often flying in a V pattern. The geese at the back do not have to flap so hard; they are pulled on by the wind of the ones at the front. Every so often, they change the leader so that the front bird, who does most work and sets the pace, can have a rest. Geese and swans are the highest-flying birds, reaching 8,000 metres or more when on migration. Geese often honk loudly while they are flying. It is thought that they do this to support the leader and help the young ones.

Birds that fly very quickly, such as swifts and swallows, have long narrow pointed wings. These birds need great speed because they eat insects, catching most of them while they are flying. These birds also migrate. They often collect in huge flocks of thousands of birds that move together like a whirling cloud.

Birds that live in bushes and branches have triangular wings that help the bird change direction. Many forest birds are expert at getting up speed by flapping and then gliding steadily among the trees, tilting to avoid things as they go. Members of the kingfisher family are expert at this type of flying.

Birds such as owls that hunt at night have wings with soft rounded feathers so that they do not flap loudly. Birds that are awake at night are called nocturnal birds. Birds that are awake during the day are diurnal.

A wandering albatross and Arctic tern might spend several years without coming to land. They can sleep while gliding and have wings which, when they are stretched right out, look like the wings of a jet plane.

Bird like chickens that feed mainly on the ground and only use their wings to fly to safety have small wings.

Flocks of birds can be very highly organised in a way that takes care of all the flock members. Studies of small flocking birds like tree sparrows show that they clearly communicate with each other, as sometimes thousands of birds may fly in close formation and spiral patterns without colliding (or flying into each other).

Two common behaviours in flocking birds are guarding and reconnaissance. When a flock of birds is feeding it is common for one bird to perch on a high place to keep guard over the flock. In the same way, when a flock is asleep, often, one bird will remain awake. It is also common for large flocks to send one or two birds ahead of them when they are flying to a new area. The look-out birds can spy the lie of the land to find food, water and good places to perch.

Flightless birds

Ostriches and emus do not need to fly because although they feed and nest on the ground, their great size and their speed is their protection. Some other ground-feeding birds have not been so lucky. Some birds such as the dodo and the kiwi were ground-feeding birds that lived in safety on islands where there was nothing dangerous to eat them. They lost the power of flight. Kiwis are endangered because European settlement to New Zealand brought animals like cats, dogs and rats which kill kiwis and eat their eggs. However, kiwis and also the rare New Zealand ground parrot have survived. In the case of dodos, they were fat and delicious. They were killed and eaten by sailors until there was none left. Other flightless birds which have disappeared are the great auk and the moa.

Penguins spend a great deal of time at sea, where they are in danger from seals. On land, they usually live in areas where there were few dangers, until the arrival of European settlers with dogs and cats. Their wings have adapted to life in the sea and have become flippers which help them in swimming very fast.

Reproduction

Although birds are warm-blooded creatures like mammals, they do not give birth to live babies. They lay eggs like lizards do. Unlike most reptiles, the shell of a bird's egg is hard. The baby bird grows inside the egg and after a few weeks, breaks out, or hatches.

Birds in cold climates usually have a breeding season once a year in the spring. Migratory birds can have two springs and two mating seasons in a year. So can birds that live in hot climates.

When the breeding season arrives, the birds choose partners. Some birds are mated for life, like married couples. These birds include pigeons, geese, and cranes. Other birds look for new partners each year and sometimes a male bird or cock will have several wives.

For birds that choose new mates, part of the breeding season is display. The male bird will do all sorts of things to attract females. These include singing, dancing, showing off the feathers and building a beautiful nest. Some male birds have splendid feathers for attracting females. The most famous is the peacock who can spread the feathers above his tail into a huge fan.

When the nest has been prepared, the birds mate so that the eggs are fertilised and the chicks will start growing. Unlike mammals, birds only have one opening as the exit hole for body fluids, and for reproduction. The opening is called the cloaca. A female bird, called a hen, has two ovaries, of which the left one usually produces eggs.

Once the hen has mated, she produces fertile eggs which have chicks growing inside them. She lays the eggs in the nest. There might be just one egg or a number of them, called a clutch. Emus might lay as many as fifteen huge dark green eggs in a clutch. After the eggs are laid, they are incubated, or kept warm so the chicks form inside. Most birds stay together for the whole nesting season, and one advantage is that the work is shared. Many birds take turns sitting on the eggs, so that each adult can feed.

This is not always the case. With emus, the male does all the sitting and all the baby-minding. With emperor penguins it is also the male that cares for the egg. There is only one egg, which he keeps on his feet and under his feathers, standing in a big group of males without feeding until the chick is hatched. While the eggs are hatching, the females are at sea, feeding, so that they can care for the chicks when they return.

Many small birds take 2-4 weeks to hatch eggs. Albatrosses take 80 days. During this time the female loses a lot of her body weight.

The quickest hatching time is for the cuckoo. Some types of cuckoos take only 10 days. This means that when they hatch in the nest of their 'foster parents', the eggs that the parents have laid are not yet ready. Newborn cuckoos are naked, blind and ugly, but they are strong. They get under any eggs that are in the nest and throw them out before they hatch. That means that the cuckoo has the whole care of both parents. Baby cuckoos grow fast and often get bigger than the parents who feed them.

When baby birds hatch, in most types of birds, they are fed by both parents, and sometimes by older aunties as well. Their mouths are open all the time and are often very brightly coloured, which acts as a ' releaser', a trigger which stimulates the parent to feed them. For birds that eat grain and fruit, the parents eat and partly digest the food for the babies. It is then vomitted carefully into the baby's mouth.

Many birds, particularly those that mate for life, are very sociable and keep together in a family group which might be anything from 4 or 6 adult birds and their young to a very large flock.

As chicks grow they change the fluffy down that covers them as babies for real feathers. At this stage they are called fledglings. Other family members may help care for fledgling chicks, feeding them, and protecting them from attack while parents are feeding. When the fledglings have their new feathers, they come out of the nest to learn to fly. In some types of birds, like pigeons, the parents watch over this and as the young ones get stronger, will give them flying lessons, teaching them how to glide, how to fly in spirals and how to land like an expert.

Communication

Most birds are social animals, at least part of the time. They communicate to each other using sounds and displays.

Almost all birds make sounds to communicate. The types of noises that vary greatly. Some birds can sing, and they are called songbirds. Examples are robins, larks, canaries, thrushes, nightingales and crows. Birds that are not songbirds include pigeons, seagulls, eagles, owls and ducks. Parrots are not songbirds, even though they can be taught to sing human songs.

All birds make noises ('bird vocalisation'), but not all sing. Songbirds are passerines, many of which have beautiful melodic songs. Songs have different functions. Danger cries are different from territorial songs, and mating calls are a third type. Fledgling may also have different calls from adults. Recognition calls for partners are quite common.

As to where the song comes from, there are three kinds of species:

Those where the song is entirely inherited, and the bird always sings the same song in the same situations.

Those where the song is partly inherited, but the bird tunes it in by copying others. In this case the slight differences between the calls of different birds may be used by partners for identification.

Those where the song is entirely learnt, and the bird often copies sounds from its environment.

Most singing birds that are kept as pets, like canaries, have several tunes and some variations.

Lorenz's studies

The Austrian naturalist Konrad Lorenz studied the way in which birds communicate, or talk to each other. He found that each type of bird had a number of sounds which they made automatically, when ever they felt a certain way. Every sound had an action that went with it. So, if the bird was frightened, it acted frightened and made a frightened sound. This told the other birds around it that something frightening was happening.

If a flock of birds were flying over a field, they would be calling "Fly! Fly!" But a hungry bird, seeing something good to eat down below might start calling "Food! Food!" If other birds were also hungry, they would make the same call until more birds were calling "Food! Food!" than "Fly! Fly!". At this point, the mind of the flock would be changed. Some of the birds would start to yell "Fly downwards! Fly downwards!" as they sank from the sky, until the whole flock was all noisily calling the same thing.

These communication sounds are often short hard sounds like chirps, squeaks, squawks. and twitters. Sometimes the calls are longer and more musical. They include the "Rookety-coo" sound of a pigeon and the "Cockadoodledoo!" of a rooster. The bird cannot change these sounds. They always make them in the same way. The bird is locked into making each sound every time a particular idea comes into its head. The connection between how they feel and how they call is innate: they are born with it. Some calls in some species are learnt. Then, it is the tendency to learn which is inherited.

The Jackdaw of Altenberg

Konrad Lorenz noticed that when birds sing, they often use a lot of their regular calls as part of the song. Lorenz had a flock of jackdaws which were scattered during World War II. One day, an old bird returned. For many months she sat on the chimney singing her song, but in the song she kept making the call which Lorenz knew meant "Come home! Come home!" One day, to the great surprise of Lorenz, a male bird flew from a passing flock and joined her on the chimney. Lorenz was sure that it was her long-lost "husband" who had found his way home at last.

Evolution and taxonomy

Palaeontologists have found some exceptional places ( lagerstätten) where fossils of early birds are found. The preservation is so good that on the best examples impressions of their feathers can be seen, and sometimes even the remains of meals they have eaten. From these remains we know that birds evolved from small carnivorous dinosaurs ( theropods) in the Jurassic period. They radiated into a huge variety in the Lower Cretaceous. At the same time, their direct competitors, the pterosaurs, dwindled in numbers and variety, and became extinct at the end of the Mesozoic.

Birds are classified by taxonomists as 'Aves' ( Avialae). Birds are the only living descendants of dinosaurs (strictly speaking, they are dinosaurs). Birds and Crocodilia are the only living members of the once-dominant Archosaur reptiles.

The class Aves is now defined as all the descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica.

The first bird-like creatures

Archaeopteryx, from the Upper Jurassic (some 150-145 million years ago), is the earliest bird which could fly. It is famous, because it was one of the first important fossils found after Charles Darwin published his ideas about evolution in the 19th century. By modern standards, Archaeopteryx could not fly very well. Other early fossil birds are, for example, Confuciusornis, Anchiornis huxlei, and other Paraves.

Many fossils of early birds and small dinosaurs have been discovered in the Liaoning Province of Northeast China. The fossils show that most small theropod dinosaurs had feathers. These deposits have preserved them so well that the impressions of their feathers can be clearly seen. This leads us to think that feathers evolved first as heat insulation, and only later for flight. The origin of birds lies in these small feathered dinosaurs.

Birds and people

Some birds are eaten as food. Most usually it is the chicken and its eggs, but people often also eat geese, pheasants, turkeys and ducks. Other birds are sometimes eaten are emus, ostriches, pigeons, grouse, quails, doves, woodcocks, and even songbirds. Some species have died out because they have been hunted for food, for example the dodo, and the passenger pigeon.

Many species have learned how to get food from people. The number of birds of these species has grown because of it. Seagulls and crows find food from garbage dumps. The feral pigeon ( Columba livia), sparrows ( Passer domesticus and starlings ( Sturnus vulgaris) live in large numbers in towns and cities all over the world.

Sometimes people also use working birds. For example, homing pigeons carry messages. Nowadays people sometimes race them for sport. People also use falcons for hunting, and cormorants for fishing. In the past, people in mines often used a canary to see if there were bad gas methane in the air.

People can catch some bird diseases, for example psittacosis, salmonellosis, campylobacteriosis, Newcastle's disease, mycobacteriosis, influenza, giardiasis, and cryptosporiadiosis. In 2005, there was an epidemic of bird influenza spreading through some parts of the world, often called avian flu.

Some people have birdboxes in their gardens to give birds a place to nest and bird tables where birds can get food and water in very cold or very dry weather. This lets people see some small birds close up which are normally hidden away in bushes and trees.

Gallery of well-known small birds

Images for kids

Confuciusornis sanctus, a Cretaceous bird from China that lived 125 million years ago, is the oldest known bird to have a beak.

Ichthyornis, which lived 93 million years ago, was the first known prehistoric bird relative preserved with teeth.

The 3 of Birds by the Master of the Playing Cards, 15th-century Germany

In Spanish: Aves para niños

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com

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Amphibians are animals that live on land and in water. 'Amphibian' comes from two Greek words: "amphi" and "bio". Amphi means "both". Bio means "life". Amphibians are members of the class Amphibia.

The living ones are frogs (including toads), salamanders (including newts) and caecilians. They are four-legged vertebrates which are cold blooded.

Amphibians lay their eggs in water, usually in a foam nest. After hatching they are tadpoles which live in the water and have gills. The tadpoles change into adults in a process called metamorphosis. When they are adults, they have lungs to breathe instead of gills and legs. Adult amphibians also use their skin to take in oxygen, and some species of salamanders do not have lungs.

They laid cleidoic eggs, which had hard shells, and could be laid out of water. Most of the large, early, amphibians went extinct in the Triassic period; a few survived to the Lower Cretaceous. Some amphibians, such as the common coquí, lay eggs out of water (in this case, on palm leaves). The eggs develop directly into adult frogs, by-passing the tadpole stage.

The only living amphibiana today are the Lissamphibia. These include the Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians). They are all rather small, compared with mammals or reptiles. The smallest frog and vertebrate in the world is the New Guinea frog ( Paedophryne amauensis). The biggest amphibian is the Chinese Giant Salamander ( Andrias davidianus).

Amphibia are world-wide, except Antarctica, though restricted in distribution by their need for moist or watery habitats to reproduce. There are about 5,565 different species: 88% of them are in the Anura.

Description

Amphibians like to live near freshwater in warm weather. There have also been species which live in forests, deserts and arctic conditions. Adult amphibians use lungs, and they also get oxygen through their skin, so long as it is moist.

Amphibians have color vision and depth of focus for clear sight. They also have eyelids, glands and ducts which keep the eyes moist. These are adaptations to life on land: amphibia were the first vertebrates to have these features.

The order Anura includes the frogs and toads. There is no fundamental difference between frogs and toads.

Frogs have a short body, webbed digits (fingers or toes), protruding eyes, forked tongue and no tail.

They are exceptional jumpers: many of their features, particularly their long, powerful legs, are adaptations to improve jumping performance. They often live in semi-aquatic or inhabit humid areas.

These features have evolved a number of times independently: convergent evolution.

The order Caudata is the salamanders.

Newts are salamanders which spend their life in the water even though they are adults. They are classified in the subfamily Pleurodelinae of the family Salamandridae. The California newt can survive a fire by spreading its mucous over its body.

Some terrestrial species lack both lungs and gills and perform gas exchange through their skin. Even some species with lungs also respire through the skin in this manner.

The skin of salamanders secretes mucus. This helps to keep the animal moist when on dry land, keeps their salt balance while in water, and lubricates during swimming.

Axolotls, from the genus (or mole salamanders), are neotenic amphibians. This means they reach maturity and reproduce while still in a larval form.

The second line of defense is to shed their tail, which can grow again. The tail wriggles a bit, attracts the predator while salamander moves off.

Gymnophiona

They are burrowing amphibians, though some are aquatic, this means that they dig themselves in wet soil like worms. Their heads are strong and have bones that help them dig. Because caecilians have a lot of vertebrae, they can bend easily.

Caecilians are found in tropical Africa, Asia and Central and South America. There are 171 different species.

Reproduction

Amphibians are the only vertebrates to go through metamorphosis. This means that their young look different from their adult. Amphibians usually reproduce in early spring to late summer, though some reproduce in winter and fall.

Most frogs and toads, such as the common frog ( Rana temporalis), gather in large groups to ponds, rivers, swamps and lakes to breed. Male frogs and toads may croak to attract a female.

Frogs can lay up to 100 to 60,000 eggs in one clutch. This is called "frogspawn".

Amphibia's reproduction is one way or another, tied to water, this is because their eggs, although covered by jelly, cannot survive long in dry conditions.

Tree frogs usually lay their eggs on a leaf in a rainwater pool. Bullfrogs, such as the male American bullfrog and the male African bullfrog, stay with their tadpoles and protect them from predators.

They also move their tadpoles by using their nose to dig a channel to another place where there is more water. They do this so their tadpoles do not dry up.

Most amphibians leave their eggs to look after themselves. Fish and other animals eat most of their eggs. Male midwife toads carry their eggs on their backs. When they are ready to hatch, the toad goes back to the water and release them.

The eggs of the spadefoot toad hatches in three days. Their tadpoles complete their metamorphosis in six to eight days. The reason for this is because spadefoot toads lay their eggs in places where water will dry up soon.

Tadpoles of frogs and toads start to grow their back legs first. They then grow front legs a few weeks later. When tadpoles grow their limbs they are called "froglets". This is because they look rather like a smaller version of adult frogs and toads. Their tails continue to get shorter until there is nothing left of them.

Salamanders and newts can be found living in streams. Salamanders can be found in rotten logs, holes or underground places that are wet such as under leaves. Web-toed salamanders live in habitats where there are a lot of rocks. They like to hide under rocks and stones.

The tailed frogs, like to live in cold water habitats. In their habitat, amphibians like to live where there are a lot of places to hide. These include nearby small trees, logs and plants. While underwater they like to hide near aquatic plants and rocks. Tree and dart frogs like to live in forests on trees, plants and on the ground under leaves.

They use their mucus to keep them wet. The mucus will harden to keep the water it produces from escaping. Once it has done this, it will stay in its cocoon and will not move. They will stay like this for several months to years until a rainstorm.

The spadefoot toad will spit on the ground. Once they have done this, they will lay on it. Their bodies will take in the water. Their bodies are thin and have a lot of blood vessels, this helps them to be able to take water through their skin.

Arctic frogs such as the wood frog, moor frog and the common frog have to live with freezing temperatures for a long time. They will burrow in places where they can get into a cocoon. Like every living organisms, amphibians must have water to survive.

Amphibians however, need freshwater. Some frogs such as burrowing frogs can keep water in their bladders. This allows them to stay underground without drying up.

Amphibians are predatory animals. They mostly eat live invertebrates and animals that do not move too quickly. These include caterpillars, earthworms, crayfish, water beetles, snails and dragon fly larvae.

Many amphibians use their sticky tongues to catch their prey. They will swallow the animal whole, but may chew it just a bit for it to go down their throats.

Most frogs are cannibalistic, and will eat each other if food is no where to be found. Some amphibians will even eat their own tadpoles and eggs if there is no food for them.

Conservation

The amphibian population have been decreasing from all locations in the world. Scientists have said that the declining of amphibians is one of the most critical threats to global biodiversity.

Ultraviolet radiation damages the skin, eyes and eggs of amphibians.

Bullfrog legs are a source of food for Southern United States and the Midwestern United States. In the state of California, people must have a license to catch bullfrogs for food. People hunt bullfrogs at night near rivers. The bullfrogs' legs are cooked, while their backs are fried.

In China, bullfrogs are sold alive for eating. However, they are later cooked dead with vegetables. The emperor newt is hunted in China for food. They are also used there for medicine.

Amphibians are also kept as pets. They are kept in aquariums or a terrarium.

Related pages

Images for kids

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Amphibians are animals that live on land and in water. 'Amphibian' comes from two Greek words: "amphi" and "bio". Amphi means "both". Bio means "life". Amphibians are members of the class Amphibia. The living ones are frogs (including toads), salamanders (including newts) and caecilians. They are four-legged vertebrates which are cold blooded.

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com

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Reptile is the common name for one of the main groups of land vertebrates. It is not used so much by biologists, who use more accurate terms.

The name "reptile" comes from Latin and means "one who creeps". All living reptile species are cold blooded, have scaly skin, and lay cleidoic eggs. They excrete uric acid (instead of urea), and have a cloaca. A cloaca is a shared opening for the anus, urinary tract and reproductive ducts. Reptiles also share an arrangement of the heart and major blood vessels which is different from that of mammals.

Many important groups of reptiles are now extinct. The great marine reptiles of the Mesozoic era, the ichthyosaurs, plesiosaurs and mosasaurs, are extinct. We used to say the dinosaurs were extinct, but they survive in the form of their feathered descendants ( birds). Ancient reptiles that do survive include the turtles, the crocodiles and the , the lone survivor of its group. The great majority of present-day reptiles are snakes and lizards.

The study of living reptiles is called herpetology.

Birds in relation to reptiles

Some reptiles are more closely related to birds than they are to other reptiles. Crocodiles are more closely related to birds than they are to lizards. Theropod dinosaurs are even more closely related, because birds evolved from them.

Cladistic writers prefer a more unified (monophyletic) grouping. This puts the birds (over 10,000 species) with what people normally call reptiles. (see Sauropsida)

Circulatory

Most reptiles have a three-chambered heart consisting of two atria, one variably partitioned ventricle, and two aortas that lead to the systemic circulation. The degree of mixing of oxygenated and deoxygenated blood in the three-chambered heart varies depending on the species and physiological state. Under different conditions, deoxygenated blood can be shunted back to the body or oxygenated blood can be shunted back to the lungs. This variation in blood flow has been hypothesized to allow more effective thermoregulation and longer diving times for aquatic species, but has not been shown to be a fitness advantage.

There are some interesting exceptions to the general physiology. For instance, crocodilians have an anatomically four-chambered heart, but also have two systemic aortas and are therefore capable of bypassing only their pulmonary circulation. Also, some snake and lizard species (e.g., pythons and monitor lizards) have three-chambered hearts that become functionally four-chambered hearts during contraction. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Because of this ridge, some of these squamates are capable of producing ventricular pressure differentials that are equivalent to those seen in mammalian and avian hearts.

Respiratory

Reptilian lungs

All reptiles breathe using lungs. Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange. Even with these adaptations, breathing is never fully accomplished without lungs. Lung ventilation is accomplished differently in each main reptile group. In squamates, the lungs are ventilated almost exclusively by the axial musculature. This is also the same musculature that is used during locomotion. Because of this constraint, most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing." This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs. Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand. This type of diaphragmatic setup has been referred to as the "hepatic piston."

Turtles and tortoises

How turtles and tortoises breathe has been the subject of much study. To date, only a few species have been studied thoroughly enough to get an idea of how turtles do it. The results indicate that turtles and tortoises have found a variety of solutions to this problem. The difficulty is that most turtle shells are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Some turtles such as the Indian flapshell ( Lissemys punctata) have a sheet of muscle that envelops the lungs. When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Turtle lungs are attached to the inside of the top of the shell (carapace), with the bottom of the lungs attached (via connective tissue) to the rest of the viscera. By using a series of special muscles (roughly equivalent to a diaphragm), turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs (indeed, many of the muscles expand into the limb pockets during contraction). Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches. They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements (Landberg et al., 2003). They are probably using their abdominal muscles to breathe during locomotion. The last species to have been studied is the red-eared slider, which also breathes during locomotion, but takes smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus. Box turtles have also been observed to breathe while completely sealed up inside their shells (ibid.).

Most reptiles lack a secondary palate, meaning that they must hold their breath while swallowing. Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains against damage by struggling prey). Skinks (family Scincidae) also have evolved a bony secondary palate, to varying degrees. Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation.

Reptilian skin is covered in a horny epidermis, making it watertight and enabling reptiles to live on dry land, in contrast to amphibians. Compared to mammalian skin, that of reptiles is rather thin and lacks the thick dermal layer that produces leather in mammals. Exposed parts of reptiles are protected by scales or scutes, sometimes with a bony base, forming armor. In lepidosaurians such as lizards and snakes, the whole skin is covered in overlapping epidermal scales. Such scales were once thought to be typical of the class Reptilia as a whole, but are now known to occur only in lepidosaurians. The scales found in turtles and crocodiles are of dermal, rather than epidermal, origin and are properly termed scutes. In turtles, the body is hidden inside a hard shell composed of fused scutes.

Excretion is performed mainly by two small kidneys. In diapsids, uric acid is the main nitrogenous waste product; turtles, like mammals, excrete mainly urea. Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure called a loop of Henle, which is present in the nephrons of birds and mammals,. Because of this, many reptiles use the colon to aid in the reabsorption of water. Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt glands in some reptiles.

Nervous system

The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Most typical sense organs are well developed with certain exceptions, most notably the snake's lack of external ears (middle and inner ears are present). There are twelve pairs of cranial nerves. Due to their short cochlea, reptiles use electrical tuning to expand their range of audible frequencies.

Reptiles are generally considered less intelligent than mammals and birds. The size of their brain relative to their body is much less than that of mammals, the encephalization quotient being about one tenth of that of mammals. Crocodiles have relatively larger brains and show a fairly complex social structure. Larger lizards like the monitors are known to exhibit complex behavior, including cooperation. The Komodo dragon is known to engage in play.

Most reptiles are diurnal animals. The vision is typically adapted to daylight conditions, with color vision and more advanced visual depth perception than in amphibians and most mammals. In some species, such as blind snakes, vision is reduced. Some snakes have extra sets of visual organs (in the loosest sense of the word) in the form of pits sensitive to infrared radiation (heat). Such heat-sensitive pits are particularly well developed in the pit vipers, but are also found in boas and pythons. These pits allow the snakes to sense the body heat of birds and mammals, enabling pit vipers to hunt rodents in the dark.

Reproductive

Most reptiles reproduce sexually, though some are capable of asexual reproduction. All reproductive activity occurs through the cloaca, the single exit/entrance at the base of the tail where waste is also eliminated.

Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion, chorion, and allantois are present during embryonic life. There are no larval stages of development. Viviparity and ovoviviparity have evolved only in squamates, and many species, including all boas and most vipers, utilize this mode of reproduction. The degree of viviparity varies: some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, and yet others lack any yolk and provide all nutrients via a structure similar to the mammalian placenta.

Asexual reproduction has been identified in squamates in six families of lizards and one snake. In some species of squamates, a population of females is able to produce a unisexual diploid clone of the mother. This form of asexual reproduction, called parthenogenesis, occurs in several species of gecko, and is particularly widespread in the teiids (especially Aspidocelis) and lacertids ( Lacerta). In captivity, Komodo dragons (Varanidae) have reproduced by parthenogenesis.

Parthenogenetic species are suspected to occur among chameleons, agamids, xantusiids, and typhlopids.

Some reptiles exhibit temperature-dependent sex determination (TDSD), in which the incubation temperature determines whether a particular egg hatches as male or female. TDSD is most common in turtles and crocodiles, but also occurs in lizards and tuataras. To date, there has been no confirmation of whether TDSD occurs in snakes.

Most reptiles are eat meat and have rather simple and comparatively short guts, meat being fairly simple to break down and digest. Digestion is slower than in mammals, reflecting their lower metabolism and their inability to divide and masticate their food. Being poikilotherms (with varying body temperature regulated by their environment), their energy requirement is about a fifth to a tenth of that of a mammal of the same size. Large reptiles like crocodiles and the large constrictors can live from a single large meal for months, digesting it slowly.

While modern reptiles are predominately carnivorous, during the early history of reptiles several groups produced a herbivorous megafauna: in the Paleozoic the pareiasaurs and the synapsid dicynodonts, and in the Mesozoic several lines of dinosaurs. Today the turtles are the only predominantly herbivorous reptile group, but several lines of agams and iguanas have evolved to live wholly or partly on plants.

Herbivorous reptiles face the same problems of mastication as herbivorous mammals but, lacking the complex teeth of mammals, many species swallow rocks and pebbles (so called gastroliths) to aid in digestion: The rocks are washed around in the stomach, helping to grind up plant matter. Fossil gastroliths have been found associated with sauropods. Sea turtles, crocodiles, and marine iguanas also use gastroliths as ballast, helping them to dive.

Defense mechanisms

Many small reptiles such as snakes and lizards which live on the ground or in the water are vulnerable to being preyed on by all kinds of carnivorous animals. Thus avoidance is the most common form of defense in reptiles. At the first sign of danger, most snakes and lizards crawl away into the undergrowth, and turtles and crocodiles will plunge into water and sink out of sight.

Reptiles may also avoid confrontation through camouflage. Using a variety of grays, greens, and browns, these animals can blend remarkably well into the background of their natural environment.

If the danger arises so suddenly that flight may be harmful, then crocodiles, turtles, some lizards, and some snakes hiss loudly when confronted by an enemy. Rattlesnakes rapidly vibrate the tip of the tail, which is composed of a series of nested, hollow beads.

If all this does not deter an enemy, different species will adopt different defensive tactics.

Snakes use a complicated set of behaviors when attacked. Some will first elevate their head and spread out the skin of their neck in an effort to look bigger and more threatening. Failure of this may lead to other measures practiced particularly by cobras, vipers, and closely related species, who use venom to attack. The venom is modified saliva, delivered through fangs.

When a crocodile is concerned about its safety, it will gape to expose the teeth and yellow tongue. If this doesn't work, the crocodile gets a little more agitated and typically begins to make hissing sounds. After this, the crocodile starts to get serious, changing its posture dramatically to make itself look more intimidating. The body is inflated to increase apparent size. If absolutely necessary it may decide to attack an enemy.

Some species try and bite, some will use their heads as sledgehammers and literally smash an opponent, some will rush or swim toward the threat from a distance, even chasing them onto land or galloping after them.

Geckos, skinks, and other lizards that are captured by the tail will shed part of the tail structure through a process called autotomy and thus be able to flee. The detached tail will continue to wiggle, creating a deceptive sense of continued struggle and distracting the predator's attention from the fleeing prey animal. The animal can partially regenerate its tail over a period of weeks. The new section will contain cartilage rather than bone, and the skin may be distinctly discolored compared to the rest of the body.

Living reptiles

Images for kids

Reptiles, from Nouveau Larousse Illustré, 1897-1904, notice the inclusion of amphibians (below the crocodiles)

"Antediluvian monster", a Mosasaurus discovered in a Maastricht limestone quarry, 1770 (contemporary engraving)

The first reptiles had an anapsid type of skull roof, as seen in the Permian genus Captorhinus

Phylogenetic classifications group the traditional "mammal-like reptiles", like this Varanodon, with other synapsids, not with extant reptiles

Varanus priscus was a giant carnivorous goanna lizard, perhaps as long as 7 metres and weighing up to 1940 kilograms

Skeleton of Champsosaurus, a choristodere, the latest surviving order of extinct reptiles. The last known choristoderes are known from the Miocene, around 11.3 million years ago

A colubrid snake, Dolichophis jugularis, eating a legless lizard, Pseudopus apodus. Most reptiles are carnivorous, and many primarily eat other reptiles and small mammals.

In Spanish: Reptilia para niños

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Marsupials are the main part of an infraclass of mammals called the Metatheria. This consists of the marsupials and their extinct ancestors.

Reproduction

Marsupials give birth to living babies. The babies are called joeys. The babies feed on milk. Their babies are born very small.

Marsupials have a special pouch where they carry their babies. After the birth the baby goes into its mother's pouch, where it can drink milk and is kept warm and safe. When the babies are young they stay in the pouch all the time, but when they are older they can leave it for short times. When they are old enough and too big for the pouch they do not go into their mother's pouch anymore.

Biogeography

Marsupials evolved before the southern supercontinent Gondwana broke off from Pangaea 100 million years ago. Early marsupial fossils have been found in Asia, from 125 million years ago.

They were outcompeted on Laurasia by placental mammals, but the placentals did not get into the Australasian part of Gondwana before it broke away into a separate supercontinent. That is why marsupials now found native only on the southern continents of Australasia and South and Central America, with the single exception of the Virginia Opossum.

Some of the 100 living species of South American marsupials have migrated north: 13 species to Central America and one to North America.

There are 334 species of living Australasian marsupials. They are mostly in Australia and New Guinea, and some are on the smaller islands.

In more recent times the land bridge between the Americas, and reintroductions to Australia, have brought in placental mammals. They have caused the recent extinction of many marsupial species.

Phylogenetic relationships

Comprising over 300 extant species, several attempts have been made to accurately interpret the phylogenetic relationships among the different marsupial orders. Studies differ on whether Didelphimorphia or Paucituberculata is the sister group to all other marsupials. Though the order Microbiotheria (which has only one species, the monito del monte) is found in South America, morphological similarities suggest it is closely related to Australian marsupials. Molecular analyses in 2010 and 2011 identified Microbiotheria as the sister group to all Australian marsupials. However, the relations among the four Australidelphid orders are not as well understood. The cladogram below, depicting the relationships among the various marsupial orders, is based on a 2015 phylogenetic study.

DNA evidence supports a South American origin for marsupials, with Australian marsupials arising from a single Gondwanan migration of marsupials from South America to Australia. There are many small arboreal species in each group. The term " opossum" is used to refer to American species (though "possum" is a common diminutive), while similar Australian species are properly called "possums".

Marsupials have the typical characteristics of mammals-e.g., mammary glands, three middle ear bones, and true hair. There are, however, striking differences as well as a number of anatomical features that separate them from Eutherians.

In addition to the front pouch, which contains multiple nipples for the protection and sustenance of their young, marsupials have other common structural features. Ossified patellae are absent in most modern marsupials (though a small number of exceptions are reported) and epipubic bones are present. Marsupials (and monotremes) also lack a gross communication ( corpus callosum) between the right and left brain hemispheres.

Description

Skull and teeth

The skull has peculiarities in comparison to placental mammals. In general, the skull is relatively small and tight. Holes ( foramen lacrimale) are located in the front of the orbit. The cheekbone is enlarged and extends further to the rear. The angular extension ( processus angularis) of the lower jaw is bent toward the center. Another feature is the hard palate which, in contrast to the placental mammals' foramina, always have more openings. The teeth differ from that of placental mammals, so that all taxa except wombats have a different number of incisors in the upper and lower jaws. The early marsupials had a dental formula from 5 / 4-1 / 1-3 / 3-4 / 4, that is, per pine half; they have five maxilla or four mandibular incisors, one canine, three premolars and four molars, for a total of 50 teeth. Some taxa, such as the opossum, have the original number of teeth. In other groups the number of teeth is reduced. Marsupials in many cases have 40 to 50 teeth, significantly more than placental mammals. The upper jaw has a high number of incisors, up to ten, and they have more molars than premolars. The second set of teeth grows in only at the 3rd premolar: all remaining teeth are already created as permanent teeth.

Few general characteristics describe their skeleton. In addition to details in the construction of the ankle, bones ( Ossa epubica) are characteristic, two from the pubic bone of the pelvis, which is a forwardly projecting bone. Since these are present in males and pouchless species, it is believed that they originally had nothing to do with reproduction, but served in the muscular approach to the movement of the hind limbs. This could be explained by an original feature of mammals, as these epipubic bones are also found in monotremes. Marsupial reproductive organs differ from the placentalp mammals. For them, the reproductive tract is doubled. The females have two uteri and two vaginas, and before birth, a birth canal forms between them, the median vagina. The males have a split or double penis lying in front of the scrotum.

A pouch is present in most, but not all, species. Many marsupials have a permanent bag, whereas in others the pouch develops during gestation, as with the shrew opossum, where the young are hidden only by skin folds or in the fur of the mother. The arrangement of the pouch is variable to allow the offspring to receive maximum protection. Locomotive kangaroos have a pouch opening at the front, while many others that walk or climb on all fours have the opening in the back. Usually, only females have a pouch, but the male water opossum has a pouch that is used to accommodate his genitalia while swimming or running.

General and convergences

Marsupials have adapted to many habitats, reflected in the wide variety in their build. The largest living marsupial, the red kangaroo, grows up to 1.8 metres (5.9 ft) in height and 90 kilograms (200 lb) in weight, but extinct genera, such as Diprotodon, were significantly larger and heavier. The smallest members of this group are the marsupial mice, which often reach only 5 centimetres (2.0 in) in body length.

Some species resemble placental mammals and are examples of convergent evolution. The extinct strongly resembled the placental wolf, hence its nickname "Tasmanian wolf". Flying and the associated ability to glide occurred both with marsupials (as with sugar gliders) and some placental mammals (as with flying squirrels), which developed independently. Other groups such as the kangaroo, however, do not have clear placental counterparts, though they share similarities in lifestyle and ecological niches with ruminants.

An infant marsupial is known as a joey. Marsupials have a very short gestation period (about four to five weeks), and the joey is born in an essentially fetal state. The blind, furless, miniature newborn, the size of a jelly bean, crawls across its mother's fur to make its way into the pouch, where it latches onto a teat for food. It will not re-emerge for several months, during which time it develops fully. After this period, the joey begins to spend increasing lengths of time out of the pouch, feeding and learning survival skills. However, it returns to the pouch to sleep, and if danger threatens, it will seek refuge in its mother's pouch for safety.

Joeys stay in the pouch for up to a year in some species, or until the next joey is born. A marsupial joey is unable to regulate its own body temperature and relies upon an external heat source. Until the joey is well-furred and old enough to leave the pouch, a pouch temperature of 30-32 °C (86-90 °F) must be constantly maintained.

Joeys are born with "oral shields". In species without pouches or with rudimentary pouches these are more developed than in forms with well-developed pouches, implying a role in maintaining the young attached to the mother's nipple.

List of Marsupials

Australasia

Thingodonta

The extinct genus Yalkaparidon (Order Yalkaparidontia) is a bizarre fossil found in the Oligocene/ Miocene deposits of Riversleigh, NE Australia. Its teeth are so strange that palaeontologists call it a 'Thingodont'.

South America

No longer marsupial

The borhyaenids and the sabertooth Thylacosmilus are no longer considered to be marsupials. They are sparassodont metatherians, the sister group of the marsupials.

Related pages

Images for kids

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Marsupials are the main part of an infraclass of mammals called the Metatheria. This consists of the marsupials and their extinct ancestors. Marsupials give birth to living babies. The babies are called joeys. The babies feed on milk. Their babies are born very small. Marsupials have a special pouch where they carry their babies.

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Looking for fun and interesting facts about a marsupial? Learn about this amazing mammal and discover other animals from tiny insects to giant mammals!

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com

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You probably know that you're a mammal, right? How about your dog or your cat? Yup, both mammals. What about seals or whales? Yes, even these creatures are mammals.

So what makes a mammal a mammal? All animals are characterized by how their body works, what they eat and how they have babies. Mammals have some special ways of doing things that no other animals have.

Fun Facts about Mammals for Kids

Most mammals give birth to live babies. The babies look a lot like their parents - only cuter! Mammal babies stay with their mothers, at least for a while. They drink mama's milk. This is called suckling. Duck-billed platypus is one of the few mammals that doesn't have live babies. Platypus mamas lay soft eggs that are the size of marbles!

All mammals have warm blood. That means they can warm up and cool down their bodies. Mammals control their body temperature by sweating, shivering and panting. A polar bear living in the snow has the same body temperature as a monkey in the jungle.

Mammals move in different ways. Some mammals move on four legs. Some, such as horses or big cats, can run very quickly. Bats are the only mammal that can fly. Moles have feet like a shovel for burrowing. Dolphins and whales have flippers and tails to swim with. How do you move?

Mammals have backbones. Mammals might look different, but they all have bony skeletons. These skeletons hold us up and keep us going. Animals with backbones are called vertebrates.

Mammals have hair or fur. Some fur or hair is short, some is long. Some comes in cool patterns. But, we all have it.

Mammal extinction is happening quickly. In the last 500 years, at least 75 species have become extinct. More than 25 percent are in danger of extinction.

Humans are the only animals that walk on two legs instead of four. Well, kangaroos, too, but they mostly hop.

Mammal Vocabulary

Suckling : A mama mammal's body makes rich milk to feed her baby

Warm blooded : Able to control body temperature

Shivering : When a mammal is cold, it shivers to warm up

Sweating : When an animal is hot, it sweats to cool down

Vertebrate : An animal with a backbone

Learn More About What is a Mammal

Understand even more what a mammal is in this video:

A video documentary about the different kinds of mammals in the world.

Mammal Q&A

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: What is the smallest mammal on earth?
: The bumblebee bat. This bat is the size of a bee. It lives in Thailand.

Enjoyed the Easy Science for Kids Website about Mammal info? Take the FREE & fun Mammal quiz and download FREE Mammal worksheet for kids. For lengthy info on What is a Mammal, click here.

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What is a Mammal? for Kids (All You Need to Know!) -

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Easy Science for Kids What is a Mammal? - learn fun facts about animals, the human body, our planet and much more. Fun free What is a Mammal? activities!

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DK Find Out! | Fun Facts for Kids on Animals, Earth, History and more!

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Visit DK Find Out! to learn about dinosaurs, space, animals, nature & more. Fun learning activities for kids with videos, quizzes & galleries at DKFindOut.com