My Science School

Turtles and tortoises are reptiles with shells on their backs. Most can pull their heads, legs, and tails inside the shell for protection.

Many turtles spend a lot of time in the water. They can swim much better than they can walk. The sea turtle spends almost all its time in the water and has strong flippers for swimming. These turtles eat animals and plants.

Tortoises are turtles that live only on land. They have club-like legs for walking on sand, mud, or grass. The shells of most tortoises are tall and round, while the shells of many other turtles are flat to help them glide through water. Most tortoises eat plants.

Turtles don’t watch over their eggs before they hatch. Female turtles dig holes in the mud or sand. They lay their eggs in the holes, then cover up the eggs and go away. The warm sun hatches the eggs, and the babies dig their own way out.

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It’s the middle of the night in the desert. A small lizard lies almost covered with sand. Only its head sticks out. It is using the sand like a blanket to keep its body warm during the cool night.

When the sun comes up, the lizard crawls out of the sand. It moves very slowly because it is still cold. It lies on a rock for a long time, letting the sun warm it. When its body is warm enough, the lizard dashes off to look for food.

Lizards and all other reptiles are cold-blooded. Their bodies get just as hot or cold as the air or water around them. If their bodies get cold, reptiles can’t move well. If they get too hot, reptiles die. So reptiles must spend their time playing hide-and-seek with the sun. If they are cold, they lie in warm sunshine. If they are hot, they hurry into the shade.

A reptile that lives where winters are cold moves more and more slowly as cold weather comes. The reptile curls up in the warmest hole it can find. Soon its body grows cold and stiff. It cannot move at all. Only when warm weather returns can the reptile move again.

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Have you ever seen a big, fat frog? Did its bulging eyes and raspy croak make you laugh?

Have you ever seen a tiny garden snake zipping through the grass? Were you amazed at how fast it could travel with no feet?

Snakes and frogs belong to two groups of animals called reptiles and amphibians.

Amphibians and reptiles slither, scamper, hop, or swim. Some hiss, some croak, and some make no sound at all. Some amphibians have scaly skin that feels like tree bark. Some snakes have skin that feels like warm glass. Some frogs are slimy, but most snakes are not.

Amphibians and reptiles live all over the world - in woodland forests and rain forests, the Australian outback and the African plains, and maybe in your own garden.

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Suppose you found some eggs lying on the ground. Now suppose that some little creatures with scales hatched out of them. What kind of animal would they be?

Could they be fish? Fish have scaly skin, but fish eggs do not have hard shells. Besides, most fish lay their eggs in water. So they could not be fish.

Could they be birds? Birds lay eggs, too. But birds don’t have such scaly skin. So they could not be birds.

They must be reptiles. Only reptiles have scaly skin and lay their eggs on land. Alligators, crocodiles, lizards, snakes, turtles, and tuataras are all reptiles.

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Did you ever swim wearing flippers? If so, you know that they help you swim faster. Flippers are like the webbed feet of ducks, geese, and swans. Webbed feet are like paddles. They push lots of water, so the bird can move faster.

Ducks, geese, and swans are all waterfowl. They spend most of their time in lakes, ponds, rivers, or the sea.

Different kinds of waterfowl have different ways of getting their food. Some kinds of ducks, such as mallards, wigeons, and teals, are known as dabbling ducks. To get food - water insects, snails, and water plants - a dabbling duck puts its head underwater. Its feet and tail stick straight up in the air. Swans feed this way too, but they eat mostly plants.

Ducks such as pochards, canvasbacks, and grebes are known as diving ducks. They dive underwater and eat mostly water plants.

Geese usually feed on land. They like grass, seeds, and plants. Their bills can clip off the tops of plants as neatly as a pair of scissors.

Colourful mandarin ducks often perch in trees when they aren’t swimming.

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Would you be able to grasp a tree branch with your toes and then fall asleep, without falling? No, because your feet are not made for living in trees.

Birds have feet that suit their way of life. Birds that perch on branches have toes that curl around the branch to give a tight grip. The grip is so tight that the bird doesn’t fall off even when it sleeps.

Birds that find their food in the ground have short, blunt toes like tiny rakes. They scratch the ground to turn up insects and seeds. Ducks, geese, and swans have feet like paddles to help them swim in water. Birds of prey, which eat small animals, have sharp, curved claws - just right for grabbing the creatures they hunt.

Climbing birds, like parrots and woodpeckers, have two toes pointing forwards and two toes pointing backwards. Cassowaries and most other fast-running birds have three toes on each foot.

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A baby swift is getting ready to fly. Ever since it hatched, its feathers have been getting longer. Its wings have been growing stronger. Now, the little bird is ready.

It hops to the edge of the nest. Even though it has never flown, the swift knows just what to do. It spreads its wings and pushes itself off the nest with its legs. Air pushes up on the swift’s wings and holds the little bird up. The swift begins to flap its wings. Feathers on the ends of the wings spread out and twist. This pulls air under each wing and pulls the swift forwards.

Now the little swift is tired. It lands by spreading out its wings and tail as a brake. Many birds can fly the very first time they try. Some birds, such as sparrows, need a little practice. They flutter weakly out of the nest. Before they can really fly, they hop about on the ground, flapping their wings for a few days.

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You know that all birds have feathers. Some feathers are quite beautiful. But what are feathers for? Feathers help most birds to fly, but they are important for other reasons, too.

In cold weather, a bird’s feathers make a warm winter coat. The bird fluffs up its feathers to keep its body warm. For some birds, waterproof feathers act like a raincoat. These birds can swim and dive without getting too wet and sinking.

The colours of feathers can be important, too. Bright colours help some birds attract mates. Other colours make birds blend in with their habitat so they are hard to see. Then hungry enemies won’t notice them.

All birds have wings. Wings are for flying, of course, and most birds can fly.

A bird’s wings are thin and very light. They are nothing but a few little bones and small muscles covered with thin skin and feathers.

Bird wings aren’t all the same, however. The kind of wings a bird has depends mainly on the bird’s way of life.

Inside an egg, a tiny baby bird is curled up in a ball. Its head is bigger than its body. Its eyes are closed. All the food it needs is inside the egg. The baby bird has grown so much that it fills up the egg. It is ready to hatch.

The baby bird begins to move inside the egg. The eggshell cracks, the crack grows bigger, and bits of the shell fall off. Soon there is a big hole. The baby bird wiggles through the hole. A new life has begun.

When some kinds of birds hatch, they are helpless. Their eyes are still closed and they have no feathers. They can’t stand on their tiny, weak legs. Birds such as robins and nuthatches are helpless for weeks after they hatch. They need their mothers to feed them and keep them warm. But other kinds of birds can see, walk, and hunt for food soon after they hatch, even though they cannot fly yet. Two days after hatching, a duckling can run, swim, and find food.

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It’s springtime. A bird flies by with a piece of red string in its mouth. Soon it flies by again with a twig. What is it doing? The bird is getting ready to build its nest. The nest is where the mother bird will lay her eggs. After the chicks hatch, they will stay in the nest until they grow up.

Different kinds of birds build different kinds of nests. Many birds make nests in trees. Some of these are layers of twigs piled together. Others are like bowls made of mud and grass. Nests can also be holes in tree trunks, or hanging pouches or sacs made of woven twigs and grass.

Some water birds make nests that float on water. They make the nests out of weeds and sticks and fasten them to rushes.

Some birds don’t make nests at all. Some sea birds lay their eggs on a ledge on the side of a cliff. Other birds lay their eggs in holes in the ground. And some birds lay their eggs in the nests of other birds.

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Not its wings. Some other animals have wings, too.

Not its bill. Some other animals have bills, too.

Not its eggs. Many other animals lay eggs.

Not the fact that it can fly. Some birds can’t fly.

Give up?

Feathers! All birds have feathers. In fact, birds are the only animals that have feathers.

So if it has feathers, it’s a bird!

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The Largest Mammals

A humpback whale swims near the top of the water. From time to time, it comes up for fresh air, filling its lungs. Then the whale dives down again. A few minutes later, it surfaces once more, and whoosh! the whale blows used air through the blowhole on top of its head. It breathes in again and dives.

Whales live in the water and look like fish, but they are really mammals. They are warm-blooded and feed their babies with mother’s milk. They don’t have gills like fish - they have lungs. That’s why they must come to the surface for air.

Big whales eat big things, right? Well, not all whales do. The throats of many whales are too small to swallow anything bigger than an orange! And many whales have no teeth. Baleen whales, such as right whales, gray whales, and rorquals, strain food from the water through hundreds of thin plates in their mouths. These whales eat plankton, which is made up of tiny plants and animals.

Toothed whales include sperm whales, belugas, and narwhals; dolphins and porpoises; and killer whales. These whales are meat eaters. Favorite meals include squid, crabs, lobsters, sharks, cod, and skates.

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Mammals in the Sea

Most kinds of mammals live on land. But seals, whales, and a few other mammals live in the sea. They can stay underwater for a long time, but these mammals breathe air through their lungs. They rise above the water to breathe.

Whales look so much like fish that many people think they are fish. But they are mammals. They have hair, they are warm-blooded, and their babies drink mother’s milk. Dolphins and porpoises are small whales.

Seals, sea lions, and walruses are mammals that spend much of their time in the water and some time on land. When they come onto land, they waddle about on their fins.

Another group of sea mammals includes dugongs and manatees, which are sometimes called sea cows. These animals look a bit like walruses without tusks. Instead of hind flippers, each of these animals has a wide, flattened tail.

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Flying Mammals

Here they come! And seeing those black shapes flutter against the darkening sky could give you goose-bumps.

Bats are the only mammals that can fly. Their two leathery wings are supported by arm bones and spread-out finger bones. When bats are resting, their wings fold up like umbrellas.

Most bats live in caves, usually in large groups called colonies. But sometimes they live in barns, trees, or attics, where they hang upside down by their toes!

Bats are nocturnal animals. They sleep during the day and come out to eat at night. Some people think bats are blind, but they really have good eyesight. They have to find their food in the dark. They do this by squeaking as they fly. The squeaks bounce off objects, and the bats hear the echoes.

Most bats eat moths and other insects. Some bats eat only fruit. The famous vampire bat of South America drinks blood. It bites the skin of a sleeping animal with its teeth and then laps up the blood.

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Mammal Homes

The winter wind howls. Snow falls in thick flakes. Rain soaks the ground. Hungry animals prowl. Some mammals don’t need a house of any kind. Whales don’t. Neither do many mammals with hoofs, such as elk and moose.

Some mammals look for shelter only at night or when they are giving birth. Most monkeys, for example, sleep in trees. The elephant looks for a hidden spot in which to have her baby.

But some mammals make houses to keep out the sun, wind, snow - or other animals. A beaver’s house of branches and twigs is often built in a pond. The top of the house freezes in winter, keeping out the cold and the other animals. But the bottom of the house doesn’t freeze. The beaver can go in and out to get the food it has stored there. Every animal’s house is just right for the animal that lives in it.

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