Snakes

(MS.Encarta) - Put yourself in the place of a harmless snake. You’re just lying in the grass, minding your own business, when suddenly a great big foot comes crashing down right next to your head. You take off through the grass like greased lightning. In the distance someone screams, “Snake!” Which one should be more afraid, the human or the snake?

A snake is simply a long, thin animal. It does not have arms or legs. It crawls along the ground on its belly.

Snakes are reptiles. Like all reptiles, snakes are cold-blooded. They can’t control their own body temperature, and so they have to lie in the sun to get warm and in the shade to get cool.

WHERE DO SNAKES LIVE?

Snakes live almost everywhere in the world. They live in grasslands, deserts, and rain forests. Some snakes live in water. There are no snakes, however, in Ireland, Iceland, Antarctica, or New Zealand. There are more than 2,500 species (kinds) of snakes.

HOW BIG ARE SNAKES?

The world’s smallest snake is about 5 inches (about 13 centimeters) long at full growth and weighs less than 0.1 ounce (less than 2 grams). The largest snakes are the anaconda and the reticulated python. They both can grow as long as 33 feet (10 meters) and can weigh up to 550 pounds (250 kilograms).

DO SNAKES HAVE BONES?

Like other reptiles, snakes are vertebrates—they have a backbone. A snake’s long backbone is made up of small bones called vertebrae. Snakes have between 100 and 400 vertebrae. Humans have just 32 vertebrae.

A snake’s jawbones are not attached to its skull. They are linked together by muscles and stretchy tissues called ligaments. This type of jaw lets a snake open its mouth wide and eat animals that are much larger than its head!

A SNAKE’S SKIN

The dry outer layer of a snake’s skin is made of scales. Scales give a snake its color. The color of some snakes lets them blend into their surroundings and avoid being seen. Some poisonous snakes are brightly colored to warn off enemies.

Snakes regularly shed their skin. First, a new layer of skin forms underneath the old one. Then the snake loosens the skin around its lips. Finally, the snake crawls out of its old skin. A brand new skin takes its place.

SNAKE SENSES

Snakes don’t see or hear as well as other animals. A snake has eyes but no eyelids. They have clear scales over their eyes. Most snakes can see movement, but some snakes are blind.

Snakes do not have ears. They have bones in their heads that can sense low sounds and vibrations.

Snakes have a great sense of smell. A snake flicks out its forked (divided) tongue to collect scents. It doesn’t mean the snake is hungry. The snake pulls its tongue in and sticks the forked tips into a place in the roof of its mouth called Jacobson’s organ. This way of smelling lets snakes find other snakes as well as prey (animals it hunts for food).

Pit vipers, boas, and pythons have small pits on their heads that can sense heat. These pits help a snake sense when a warm-blooded animal is near.

POISONOUS SNAKES

Most snakes will not harm people. Garter snakes and ribbon snakes are harmless snakes. But some snakes can be deadly. They inject a poison called venom when they bite. They use venom to defend themselves or to kill prey.

Poisonous snakes have two big, hollow teeth called fangs. When they bite, the venom comes down through these fangs. Pit vipers keep their fangs folded in their mouths until they are ready to strike. Rattlesnakes are a well-known kind of pit viper. Cobras and coral snakes are also very poisonous.

Spitting cobras do not have fangs. Instead, they spit poison to defend themselves. They aim their venom at the eyes. The venom can cause blindness.

Someone bitten by a poisonous snake should get medical help immediately. Snake venom can be deadly.

BOAS AND PYTHONS

Boas and pythons are kinds of snakes known as constrictors. These snakes have thick bodies and strong muscles. Instead of biting, they wrap themselves around their prey and squeeze. They squeeze so hard that the animal can’t breathe and dies.

HOW DO SNAKES MOVE?

Some snakes move by wiggling and squirming forward. Some snakes make leaping, twisting movements called sidewinding.

Snakes that live in trees coil their tail around a branch. Then they hook their neck into a higher part of the tree and pull the rest of their body up behind them.

WHAT DO SNAKES EAT?

Snakes eat a variety of things: worms, insects, lizards, small mammals, birds, and frogs. Some snakes, such as the Australian bandy-bandy, feed only on other snakes. Other snakes like to eat the eggs of other animals. An adult reticulated python eats larger prey, such as wild pigs, monkeys, and small deer.

Snakes don’t chew their food. They swallow it whole. Their teeth point backward, which helps to keep prey from escaping. Many snakes begin to swallow their prey while it’s still alive. Others kill the animals before eating them.

LIFE CYCLE OF A SNAKE

Most snakes lay eggs. Some sea snakes and snakes that live in cold places give birth to live baby snakes.

Some snakes can begin reproducing at two years of age. Others take slightly longer to mature. Snakes may live for as long as 20 to 30 years.

SNAKES AND PEOPLE

People in Asia and other places kill snakes for meat. Some people make shoes, belts, purses, and other things out of snakeskin. When people build houses and farms, the places where snakes live are often destroyed.

Scientists and other experts fear that some snakes could become endangered if the killing of snakes or the destruction of their habitat (living places) continues. Some countries have laws against killing or selling snakes for their skins or their meat.
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Spiders

“If you want to live and thrive, let a spider run alive!” That is an old English saying that means not killing spiders will bring you good luck. There is also a myth that killing a spider will bring bad weather.

Letting a spider live won’t bring you good luck or good weather. But scientists say there is no good reason to kill a spider. Most spiders will not harm you. They rarely bite. Only 30 of the 40,000 species (kinds) of spiders cause illness when they bite people. The black widow and the brown recluse are two spiders that have painful or deadly bites.

Spiders are important to the balance of nature. Spiders eat mosquitoes and other insects. Spiders help keep insects under control.

ARE SPIDERS INSECTS?

Spiders are arachnids. They are not insects. Daddy longlegs, mites, ticks, and scorpions are also arachnids.

You can tell spiders and insects apart. Spiders have eight legs. Insects have six legs.

The bodies of spiders have two parts. The head and thorax (chest) form one part, and the abdomen is the second part. The two parts are linked by a thin stalk called the pedicel. The bodies of insects, on the other hand, have three parts. A spider’s body has a hard outer shell.

Insects have antennae, and most of them have four wings. Spiders do not have any wings or antennae.

HOW BIG ARE SPIDERS?

The biggest spiders are tarantulas. They have bodies that are more than 4 inches (10 centimeters) long. A tarantula’s legs spread out over 8 inches (20 centimeters). The smallest spiders have bodies that are less than 0.04 inch (1 millimeter) long.

HOW DO SPIDERS MAKE WEBS?

Spiders spin webs out of silk threads. The silk comes from glands in the spider’s abdomen.

The glands make a liquid. The liquid goes out through tubes as thin as a hair. The tubes are called spigots. The spigots go to spinnerets on the spider’s abdomen. Dozens of spigots go to each spinneret. The spinnerets are like fingers. They can move to stick silk threads to a wall or wrap prey (animals they eat) in silk.

WHY DO SPIDERS MAKE WEBS?

House spiders, garden spiders, and other spiders spin webs to catch prey. Some webs are shaped like funnels. Some webs are flat. Some webs are like a circle. The spiders feel the web vibrate when a fly or other insect gets trapped in the web’s sticky threads.

Not all spiders spin webs, but all spiders make silk threads. Spiders leave a silk thread behind them as they go. They can use this thread to make a quick escape. Spiders use their silk to make nests.

Some spiders use their silk to wrap up captured prey. All spiders are carnivorous (meat eaters). They eat insects and sometimes other spiders.

Scientists divide spiders into two groups called web spiders and ground spiders. Ground spiders hunt their prey. Wolf spiders and other ground spiders have long, thick legs. They wait for an insect to come along and then jump on it.

HOW DO SPIDERS EAT?

A spider has special mouthparts called chelicerae. There is a sharp fang at the end of each chelicera. The fang is hollow. The spider stabs its prey with the fang. Poison from a poison gland in the spider’s body goes through the fang and into the prey. Big tarantulas are powerful enough to kill frogs and lizards. Small jumping spiders that live in the tropics can jump a long way to attack prey.

Spiders cannot chew their food. The spider spits juices into the wound made by its fang. The juices start to digest (break down) the prey outside the spider’s body. The spider’s stomach has muscles that are powerful enough to suck in the digested prey.

A spider can use its mouthparts for things other than eating. It can use them to carry prey. Ground spiders use their mouthparts to dig tunnels in the soil.

DO SPIDERS HAVE HAIR?

Some spiders have hair on their bodies. All spiders have hairs on their legs. Spiders use their hairs to feel and smell things. Each leg has seven parts with joints between them.

The hairs of many tarantulas have barbs like tiny fishhooks. Tarantulas can brush off their abdominal hairs when they feel threatened. The barbed hairs fly through the air. They cause a burning feeling if they get in your skin or up your nose.

HOW DO YOUNG SPIDERS GROW?

The male spider fertilizes eggs from a female spider. The female makes a silky cocoon for her eggs.

Some spider mothers hide their cocoons and then leave them. Other spiders guard their cocoons until the eggs hatch. Female wolf spiders carry their cocoons on their bodies until the eggs hatch.

Spider eggs hatch inside the cocoon. The young spiders go through different life stages. The first stage is as a white, wormlike larva. After about two weeks, the larva changes into a spiderling. Spiderlings look like grown-up spiders, only smaller.

Spiderlings lose their hard outer shell a number of times as they grow. A new shell takes the place of the old one. This is called molting. Small spider species may molt about 5 times. Some large tarantulas may molt as many as 40 times. The last time a spiderling molts it becomes a grown-up spider.
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Panda - Da Xiong Mao

(MS. Encarta) - Giant Panda, bamboo-eating bear that lives in forests high in the mountains of central China. As one of the rarest but most recognized animals in the world, the giant panda has become an international emblem of endangered species and wildlife conservation efforts. The Chinese name for the giant panda, da xiong mao, means “great bear-cat.”

Physical Description

he giant panda resembles other bears in general appearance, with the exception of its coloring. The giant panda is white with black patches over its eyes, ears, and legs and a black band across its shoulders. Like other bears, the giant panda has long, shaggy fur. It keeps the giant panda warm in the cold and damp forest.

Giant pandas have an enlarged wrist bone on the forefoot that functions as an opposable thumb. Their premolar teeth and molars are generally larger and broader than those of other bears, and their jaw bones and cheek muscles are exceptionally strong. These adaptations assist giant pandas in holding, crushing, and eating bamboo.

An adult giant panda usually weighs between 75 and 160 kg (between 165 and 350 lb). Males are generally 20 percent heavier than females. The giant panda grows to about 1.5 m (about 5 ft) in head-and-body length, plus a 12.5-cm (5-in) tail.

Habitat and Behavior

Giant pandas are found in the wild in the Sichuan, Gansu, and Shaanxi provinces of central China. They live in a few rugged mountain ranges at the eastern edge of the Tibetan Plateau where temperate broadleaf and coniferous forests contain dense stands of bamboo. Giant pandas are usually found at elevations between 2,300 and 3,800 m (7,500 and 12,500 ft) but will relocate to lower elevations in winter and spring. However, the zone of bamboo vegetation below 1,200 m (3,800 ft) has been cleared for agriculture in many areas, greatly restricting the giant panda’s range.

Unlike other bears that live in temperate climates, giant pandas do not hibernate. Bamboo is usually abundant and green even in winter, so they generally have no lack of food.

Although giant pandas eat bamboo, they have the digestive system of a carnivore like other bears. Their system cannot efficiently digest bamboo, so they must eat large amounts to obtain enough nutrition. A giant panda must consume between 12 and 38 kg (26 and 84 lb) of bamboo each day. It spends 10 to 16 hours a day foraging and eating. A giant panda usually feeds in a sitting position, enabling it to grasp a bamboo stalk between its “thumb” and first two digits. It strips away the bamboo’s tough outer layer with its teeth, and then slowly eats the peeled stalk. It also eats bamboo leaves, shoots, and roots. If its usual food supply is unavailable, a giant panda may feed on other plants, such as irises and crocuses, or even small animals, such as rodents.

When not eating, a giant panda spends most of its time sleeping and resting. Giant pandas seem to have no permanent den, although they find shelter and give birth in caves or hollow trees.

Giant pandas are fairly solitary most of the year. Small groups of giant pandas share a large territory and sometimes meet outside the breeding season. Both males and females may have overlapping ranges, and males show no evidence of territorial behavior other than scent-marking their routes. Giant pandas make a variety of sounds to communicate with each other, including bleats, honks, barks, growls, moans, and squeals. However, they never roar like some other bears.

Mating takes place from March to May, and the young are born during August or September. A newborn cub usually weighs only 90 to 130 g (3 to 5 oz) and is about the size of a stick of butter. Born nearly hairless and unable to open its eyes for 40 to 60 days, the cub is completely defenseless and dependent on its mother. A giant panda mother will cradle her tiny cub in one paw and hold it close to her chest, nursing it often. Nearly half of giant panda pregnancies produce twins, but only one cub usually survives in the wild because the mother will neglect the other one. In captive breeding centers, human caretakers will switch the cubs so each receives enough milk from the mother to survive.

A giant panda cub begins to walk when it is three to four months old. It starts eating bamboo around the fifth month of its life but will not be fully weaned from its mother’s milk until the eighth or ninth month. Giant panda cubs may stay with their mothers for up to three years before striking out on their own.

In the wild, a female giant panda will usually have a cub every other year for about 15 years of her life. However, many panda cubs do not survive to adulthood, and losses of young hinder the recovery of giant panda populations. Giant pandas generally live to between 20 and 35 years of age in captivity, and it is believed their lifespan is longer in the wild.
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Tigers

(MS.Encarta) - They can move silently through the forest. They can kill a huge wild boar with a single bite. Their roar sends shivers down your spine. They are perhaps the perfect killing machines. They are tigers.

TIGERS ARE HUGE CATS

Tigers are members of the cat family. Lions, leopards, cheetahs, and house cats are also members of the cat family. Tigers are the largest cats, and the only cats with stripes. They live in large forests in southern and southeastern Asia.

A tiger’s short fur is usually colored dark orange with black stripes. Each tiger has different stripes, and you can use them to tell tigers apart. The stripes make a tiger stand out if you see them in the open. In the forests where tigers live, however, the stripes make them almost invisible.

Like house cats, tigers have soft pads on the bottoms of their paws. These pads allow tigers to move silently through the forest. Tigers have long, sharp claws at the ends of their feet. They pull the claws in until they need them. When needed, the claws pop out like knives.

Their big, yellow eyes give tigers sharp sight to help find prey. Tigers see as well as people during the day, and much better than people at night. They also hear very well. They can turn their ears toward sounds.

Tigers have explosive speed. They have strong muscles and long legs that help them move extremely fast over short distances. Their long tails give them balance while running fast. Powerful jaws and sharp teeth help tigers grab and kill prey once they catch it.

Some tigers in zoos and circuses are white with blue eyes. People bred these tigers because white tigers fetch more money from tourists. In the wild, white tigers are very rare. Zoos no longer breed tigers to be white.

WHAT DO TIGERS EAT?

Tigers eat the largest animals they can catch. They hunt wild boars, deer, wild cows, young elephants, and young rhinos. Tigers also kill farmers’ cows and goats. Tigers prefer to avoid people. Sometimes they attack and kill people, but only if they can’t find other food.

HOW DO TIGERS HUNT?

Tigers hunt alone. They usually hunt at night. Tigers will travel 6 to 20 miles (10 to 30 kilometers) in one night while searching for prey.

Tigers sneak up on their prey. They use the trees and grass to hide. A tiger slowly and silently sneaks until its prey is about 30 feet (about 10 meters) away. The tiger then lunges, lightning-fast, and grabs the animal in its paws and wrestles it to the ground. It sinks its teeth into the animal’s neck to kill it.

The tiger then drags the dead animal to a hiding place. The tiger will eat for two or three days until the meat is gone. On average, a tiger must kill once every eight days to avoid starving. Even though tigers are built to hunt, they are only successful in 1 out of 10 or 20 hunts!

WHY DO TIGERS ROAR?

Tigers roar to scare other tigers away. A tiger’s roar tells other tigers to keep out of its hunting ground. Tigers also use smells and scratch marks to mark their territory.

FEW TIGERS REMAIN

Tigers are disappearing in the wild. There are less than 7,000 tigers still alive. People pose the biggest threat to tigers. People destroy the tiger’s forest home. People have taken away tigers’ food.

People also hunt tigers for sport and sell their skins and bones. Most countries have passed laws against hunting tigers, but poachers continue to kill them.

A tiger in a zoo can live to be 20 years old. A wild tiger will likely not live to be 15. Only half of the tiger cubs born live long enough to leave their mother. Adult tigers have violent fights with each other. Other animals injure and kill tigers. They can also starve to death when there is no food.

SAVING TIGERS

Many nations have passed laws to protect tigers. Scientists are trying to create more national parks for tigers to roam in and make the forests they live in bigger. Zoos also breed many tigers.
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Turtles and Tortoises

(MS.Encarta) - Turtles were crawling and swimming around when gigantic dinosaurs walked Earth. The first turtles lived about 185 million years ago. The dinosaurs died out, but turtles lived on. Many kinds of turtles still thrive today.

Tortoises are a kind of turtle that lives all its life on land. Other turtles live at least part of the time in water.

WHY DO TURTLES HAVE SHELLS?

A turtle is the only reptile with a shell. The shell is made of a bony or a leathery material. A shell is like a suit of armor. Most turtles can protect themselves by pulling their heads, necks, and legs into the shell.

The top part of the shell is called the carapace. This part covers a turtle’s back. The bottom part is called the plastron.

Most turtle shells are brown, black, or olive green. Some turtles have red, orange, yellow, or gray spots or lines on their shells. The painted turtle is very colorful. It has a yellow plastron and a black or olive carapace with red markings around its rim.

Tortoises have big, heavy shells to protect them from enemies on land. Sea turtles have light shells so they can swim more easily.

WHAT’S A TURTLE SHELL MADE OF?

Most turtles have shells that are covered with horny scales called scutes. The scutes are made from skin tissue. They overlap and make the shell hard and strong. Some turtles do not have scutes. Instead they have soft shells covered with tough skin.

The inner part of a turtle’s shell is made up of many bones. These bones include part of a turtle’s backbone and its ribs. The backbone and ribs are attached right to the shell. This is why a turtle cannot crawl out of its shell.

DIFFERENT KINDS OF TURTLES

There are about 270 species (kinds) of turtles alive today. Scientists group turtles by how they pull their heads into their shells.

Some turtles fold their necks sideways under the top of their shell. They are called side-necked turtles. Hidden-necked turtles bend their heads directly back into the shell. Sea turtles cannot pull their heads into their shells at all. But they are grouped with hidden-necked turtles.

Turtles come in all sizes. The largest turtle is the leatherback sea turtle. Its shell can be 8 feet (2.4 meters) long, and it can weigh over 2,000 pounds (900 kilograms). Other sea turtles, such as the green turtle and the loggerhead turtle, are also very large.

The largest land turtles are the giant tortoises that live on the Galápagos and Aldabra islands. They can measure 4 feet (1.2 meters) long and weigh as much as 600 pounds (270 kilograms).

Among the smallest turtles are the American mud turtles and musk turtles. Many mud and musk turtles have shells that are less than 5 inches (13 centimeters) long. The shell of the tiny speckled cape tortoise of South Africa is only 4 inches (10 centimeters) long.

A TURTLE’S BODY

The kind of limbs a turtle has depends on where it lives. Turtles that live on land have thick legs for walking. Turtles that live in water have long webbed toes for swimming. Sea turtles have flippers to paddle through the water.

All turtles have tails. Most turtles have short tails. American snapping turtles have long tails. The Asian big-headed turtle has a large, strong tail covered with scales.

Turtles, like other reptiles, breathe air through lungs. Even sea turtles must come to the surface to breathe. Some turtles can hold their breath for months at a time. They do this when they hibernate at the bottom of a pond or river during winter.

WHERE TURTLES LIVE

Turtles are cold-blooded animals. This means they cannot produce their own body heat. If it is cold outside, the turtle will be cold. If it is warm, the turtle will be warm. For this reason, turtles cannot live in very cold places, such as Antarctica. But they can live in most other places.

Side-necked turtles live in South America, Africa, and Australia. Hidden-necked turtles live in North America, Europe, and Asia. Turtles live in ponds and rivers. They live in forests and grasslands. Some turtles even live in deserts. Sea turtles live in the ocean.

WHAT TURTLES EAT

Some turtles only eat animals, such as insects, worms, and small fish. Some turtles only eat plants. Most turtles eat both animals and plants.

Turtles do not have teeth. They have a beak, similar to a bird’s, with ridges that they use to cut food. Turtles that eat animals have knife-sharp ridges for slicing through their prey. Plant-eating turtles have ridges with sawlike edges that help them cut through tough plants. Turtles have a tongue that helps them swallow food.

HOW TURTLES REPRODUCE

After mating, female turtles lay from 1 to 200 eggs on land. They dig a nest to keep the eggs safe. The baby turtles must take care of themselves as soon as they hatch from the eggs. Turtles that survive can live a long life. Some turtles can live more than 60 years. Some tortoises live to a very old age—up to 150 years!

THREATS TO TURTLES

Animals such as raccoons, snakes, and skunks love to eat turtle eggs and baby turtles. Many birds eat baby turtles as they crawl toward the sea. Fish eat baby turtles once they enter the water. Most turtles never live to grow up.

People are the biggest threat to turtles. People hunt turtles for their meat, eggs, and shells. They destroy places where turtles live by building farms and towns. They pollute the water where turtles swim. Sea turtles get trapped in fishing nets. Some species of turtles have become endangered. Many states and countries have passed laws to protect endangered turtles.
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