ANIMALS (Part 2 of 4)

Homes

Many animals build temporary or permanent homes for themselves and their young. Birds occupy their nests only while they are incubating eggs and feeding the helpless nestling’s A few fish make temporary nests for their young.

No animal dwelling has excited more wonder and interest than the lodge built by the beaver. Almost as remarkable is the dome-shaped winter home of the muskrat.

Underground burrows with sleeping rooms, food-storage rooms, connecting tunnels, and emergency exits are constructed by ground hogs, prairie dogs, European rabbits, gophers, kangaroo rats, and field mice. Chimpanzees and gorillas build temporary nests and sleeping platforms of sticks in trees. The living quarters made by the different kinds of ants can be intricate and complex. Certain tropical bats cut palm fronds in such a way that they droop to form a leafy shelter from the hot sun and torrential rains.

Defences

All animals have some means of defending themselves against enemies. A cat can usually outrun a dog and climb the nearest tree. If cornered, it will scratch and bite.

Moose, largest member of the deer family; called elk in Europe.

Many animals rely on speed, camouflage, teeth, claws, and even intimidation to escape other animals. The variety of means of protection is extensive. Porcupines and hedgehogs roll into a ball and raise their sharp quills. The quills come off and stick into the nose or paw of an unwary dog or some other enemy. Skunks spray a foul-smelling fluid from a gland when they are frightened. Deer, moose, and antelope fight with their antlers. An elephant's trunk is a powerful weapon. It can be used to pick up another animal and smash it to the ground.

Squids shoot out a cloud of inky material and escape under its cover. Torpedo fish and several other kinds of fish have built-in electric storage cells by which they can deliver a paralysing shock. Some insects, snakes, and lizards protect themselves with their venom.

Many amphibians produce poisonous skin secretions.

Many animals hide by means of protective colouration A baby deer is almost invisible in the forest because its spotted coat looks like patches of sunlight in the brown leaves. Many fishes, birds, insects, lizards, and snakes use nature's camouflage to avoid being seen.

Feeding Behaviour

Vorticella (popularly called bell animalcules), genus of bell-shaped Protozoa.

Heliozoan, any protozoan of the order Heliozoa; often called sun animalcule; a single pseudopod may engulf food or several may work together.

Cilia (plural of cilium), hairlike, vibratory appendages found in some plants and animals.

Many one-celled animals (the vorticella and collar flagellate, for example) live in water. These very tiny animals and their feeding habits can be studied only under a microscope.

They feed on even tinier organisms in the water. The vorticella is attached by its stalk to some solid object. At the upper end is a mouth surrounded by tiny hairs called cilia. The hairs sweep food particles into the mouth by setting up a whirlpool action in the water. The food is enclosed in a bubble called a food vacuole, where it is digested.

Flagellum (plural flagella), a whip like extension of certain protozoans.

The collar flagellate has a delicate, transparent collar. From the centre of it grows a whip like organ, the flagellum. The beating of the whip draws a current of water toward the cell. Food particles in the current pass through the wall of the cell into the food vacuoles.

The heliozoan, also called sun animal, moves about and captures food by means of pseudopodia. In this case the pseudopodia are stiff spines that radiate from the centre of the cell. The spines wrap around the food and enclose it in a vacuole.

Hydra, primitive water animal of the class Hydrozoa and the genus Hydra.

The hydra feeds most commonly on the larva of a kind of shellfish. It has a mouth surrounded with long tentacles. The tentacles sting and paralyse the prey and then shove it inside the mouth.

Common swallow (in North America, barn swallow), bird (Hirundo rustica).

Butterflies and moths have tube like mouth parts. With these they suck nectar from flowers. Grasshoppers and beetles have chewing, grasping, and tearing mouth parts

Birds and bats catch insects in flight. Woodpeckers hammer into the bark of trees for grubs, other birds comb the leaves with their bills for small insects, and hawks swoop down on rodents and on other birds.

The kangaroo rat is a harmless little animal that lives in the deserts of the south western United States. It lives on dry thistle and cactus leaves, seeds, and small juicy tubers that grow abundantly in the desert 1 to 2 inches (2.5 to 5 centimetres) below the surface. It collects seeds in its cheek pouches and stores them in underground chambers. Gophers and chipmunks also collect food in their cheek pouches and store it in underground pantries for future use.

Carnivores, Herbivores, Insectivores

Animals that eat other animals are called carnivores. The shark is a fierce carnivore. It lives on smaller fish, such as mackerel. Many mammals are carnivores. They all have special kinds of teeth for tearing their food into chunks and chewing it. Most of them have claws for catching and holding their prey. Among the carnivores are cats, dogs, raccoons, weasels, bears, hyenas, and civet cats. Some fish subsist on plant and animal life known as plankton. The baleen whale is an enormous animal, growing up to 100 feet long. It feeds upon shrimp like creatures only about 1 inch in length. When it finds a school of shrimp, it opens its mouth and gulps in several barrels of water. Horny strainers that hang from the roof of its mouth catch the shrimp and drain out the water.

A large group of animals are plant eaters (herbivores). Many herbivores are prey of the carnivores. Insects are the dominant herbivores in most parts of the world, although they may be less conspicuous than plant-eating mammals and birds. Herbivorous mammals include horses, cattle, sheep, goats, rabbits, rodents, elephants, deer and antelope, and monkeys and apes.

A few mammals live on insects moles, shrews, and hedgehogs, bats, armadillos, aardvarks, and anteaters. Many bird species are insect eaters, as are certain kinds of insects, such as ladybugs.

How Animals Sense Their Surroundings

The ability of animals to sense and respond to their surroundings is one way in which they differ from plants. Higher animals have sense organs to perceive light, sound, touch, taste, and smell.

Eyes are very important to most mammals. Animals that hunt and feed by night have very large eyes. Cats' eyes have pupils that can open wide in the dark and narrow down to slits in the sunlight. Insects have compound eyes, made up of tiny units that break up the image into many small pictures. They also have two or three simple eyes that probably detect motion. The eyesight of some fish is especially keen.

Fennec fox, name of several species of small, fox like animals characterized by large pointed ears.

Ears are perhaps as important as eyes to some species. The fennec is a fox like animal that lives in the Sahara and hunts by night. Its large ears help it detect its prey in the darkness of a hot, dry climate, where food may be very scarce. The cat is also a night prowler, and it too has large, erect ears. The hearing organs of the field cricket and katydid are located on their forelegs. The organ is a thin membrane that vibrates in response to sound waves.

Many animals have sense organs unlike those of the mammals. The antennae of the moths, butterflies, and other insects seem to correspond to the organs of taste, touch, smell, and hearing.

Barbel, a soft, slender feeler around mouth of certain fishes, such as catfish, cod, drum fish, goat fish,

sturgeon.

The barbels of the catfish and the whiskers of the flying squirrel and the cat are organs of touch. They are very useful for animals that explore in the dark. The lateral line of the fish is a rod of nerve cells running the length of the body. It probably helps the fish feel movements in the surrounding water.

The delicate forked tongue of the snake tastes the air. With it the snake can locate food and other snakes. The rattlesnake has sensory pits on the head through which it can detect a nearby warm-blooded animal. Even the simplest one-celled animals respond to touch. If a flatworm is touched, it may jerk away or curl up into a ball. It moves away from strong light or from water that is too hot or too cold.

In the warm, muddy rivers of Western Africa there are fish that send out small electric impulses and surround themselves with an electric field. Whenever another fish or other object approaches, the fish is made aware of it by the changes in the charged field. Thus a built-in electric system takes the place of eyesight in the dark waters and keeps the fish informed of its surroundings. Bats emit high-pitched squeaks and use the reflected sound waves to avoid objects and locate prey while flying. Dolphins and whales send out ultrasonic signals and are able to detect objects by reflections of the sound.

Migration and Hibernation

When winter comes to northern or high-mountain regions, animals must find some way to keep warm. Many birds and some mammals seek a mild climate by moving south or to lower elevations. They are said to migrate. Other kinds of mammals (bears and woodchucks, for example) store up fat in their bodies in the fall by eating all they can. Then they curl up in a cave or some other protected place and sleep during the cold period that is, they hibernate.

Most insects die in the wintertime. They leave well-protected eggs which hatch in the spring. Fishes, frogs, and aquatic arthropods and other water-dwelling animals may hibernate in mud or move to deeper water and become inactive.

Living Together in Colonies

Social insects, those living in communities and having differentiated forms or castes, as queens, workers, drones.

Some animals live with others of their own kind. Ants, honeybees and bumblebees, and wasps are called social insects because they live together in highly organized societies.

Some birds live in large colonies. Penguins, anis, and eider ducks are examples. Weaver finches work together to build huge community dwellings.

South American monkeys travel through the jungles in family groups. They scatter while they are searching for food but stay within sight or hearing of one another. Toward evening they regroup and spend the night together. Baboons live in large bands. They cooperate in getting food and post sentries to watch for danger when the group stops.