Introduction to Bat
Bats are the only flying mammals.Contrary to what many people believe, bats are not vicious and are not likely to attack humans and transmit disease. Although bats can spread rabies, fewer than one half of one per cent of them are known to have the disease. Many species of bats are extremely important to the stability of the environment and some are economically important. Insect-eating bats destroy large numbers of insects, including mosquitoes and some agricultural pests. Nectar-eating bats and fruit-eating bats transfer the pollen and disperse the seeds of numerous plants, including banana plants, peach trees, and date palms. The droppings of certain cave-dwelling bats sometimes accumulate in thick layers on the floors of caves. This material, called guano, is a valuable plant fertilizer.
Many superstitions have been associated with bats. Because they fly only at night and because they often live in tombs and abandoned churches, they have been regarded as omens of evil. The legendary vampire is a supernatural creature that changes from human form into a bat and sucks human blood.
Many people believe that bats will tangle themselves in human hair, but this belief is false.
Description
Bats are found in nearly all parts of the world except the polar regions. There are nearly 1,000 species, and they vary greatly in size, color, and appearance. The smallest bat is only about one inch (2.5 cm) long. The largest, the flying fox of the tropics, has a body one foot (30 cm) long and a wingspread of nearly six feet (1.8 m). Bats may be black, red, white, or other colors. Some have tails.
The animal's wings are formed of thick skin that stretches from the forelimbs and long digits (or "fingers") down the flanks to the hind legs. The digits serve as a framework that makes the membrane rigid. Some species have a similar membrane (the interfemoral membrane) between the hind legs.
The five toes of the hind foot and the "thumb" of the forelimb have curved claws. In some species, the second digit also has a claw. The claws on the toes support the bat when it rests, hanging head downward from a branch or roof of a shelter. Bats have large ears. Most species have a lobe, called a tragus, in front of the ear opening. The ears are sometimes larger than the body and, in some species, fold up when the animal is at rest. Some bats have sensitive leaflike folds of skin around the nose and mouth that act as sense organs.
All bats have well-developed eyes and, contrary to popular belief, can see quite well. The typical bat has a pointed face and small, sharp teeth. Bats normally live 10 to 20 years.
Habits
Bats use echolocation to find obstacles and prey.Bats typically fly at dusk or at night, searching for food. Depending on the species, they may eat insects, fruit and blossoms, small vertebrate animals, fish, or nectar. The vampire bat, which is found only in the tropics, lives on the blood of other animals, including that of humans. The natural enemies of bats are owls, hawks, snakes, and some mammals, including other bats.
During the day, bats seek out dark, sheltered places and sleep head downward, wings folded about or against their bodies. They live in large groups in trees, caves, abandoned buildings, church belfries, or under overhanging eaves. They do not have nests. With some species, a community of bats is usually all male or all female. In colder climates, bats may hibernate or migrate in winter.
Bats generally mate once a year, the female giving birth to one or two young about four months later.
A number of bat species, including the flying fox and several species of fruit bats, are either threatened with extinction or endangered.
In the 2000's, a disease called white-nose syndrome killed hundreds of thousands of hibernating bats in northeastern North America. Scientists believe the disease may be caused by a fungus.
Why Do Some Bats Like Caves?Caves are the preferred housing for many kinds of animals. Bats use caves because they offer shelter, a fairly constant temperature, many different places to roost, and protection from predators.
Different species of bats like to use caves differently. Some fruit bats hang close to a cave's entrance, so that they can easily fly out and look for fruit. But other bats, such as vampire and horseshoe bats, fly farther back into the dark recesses of caves to find places to roost.
Some types of bats like to squeeze into cracked rocks or crevices, including the insides of hollowed-out logs. Many bats even roost in attics and other human-made structures.
Are Bat Skeletons Like the Skeletons of Other Mammals?Yes, the skeletons of bats do resemble the skeletons of other mammals. A bat has hands, as do many other mammals. But, a bat's hands are not “just like” other hands—they act as wings. Each hand on a bat has a thumb and four very long fingers. The bones of the fingers support the flexible skin of the wings.
Some types of bats have tails, as do some mammals. And, like most other mammals, bats have legs. But bats' legs are usually weak. A few kinds of bats may use their legs and arms to walk, but many kinds do not walk at all. Instead, they use their legs only to hang from their roost. A bat's foot has five toes, each with a rounded, pointed claw that allows the animal to hang from a crevice or twig.
Are Bats Big or Little?There are more than 900 species (kinds) of bats. Some are very big. Others are tiny. Kitti's hog-nosed bat, for example, is only a little larger than a bumblebee. The combined length of this bat's head and body is around 1 inch (2.5 centimeters), while a bumblebee might be around 3?4 inch (1.9 centimeters) long. The Kitti's hog-nosed bat is not only the smallest kind of bat—it is one of the smallest mammals in the world. On the other hand, the largest bat in North America, the hoary bat, has a wingspan of 16 inches (40.6 centimeters).
Both of those bats are small compared to flying foxes. Flying foxes are the largest kinds of bats. The wingspan of a flying fox can stretch up to 6 feet (1.8 meters). A spectacled flying fox can have a wingspan of nearly 5 feet (1.5 meters). No wonder flying foxes and other fruit bats belong to a group known as Megachiroptera, or the “megabats.”
Flying Foxes
Flying foxes are large bats that live in the tropical regions of Africa, Australia, and Asia. They do not migrate but, instead, stay in this habitat year round. They also stay active year round. They fly from place to place, looking for roosts and food. They feed on the pollen and nectar of the buds and blossoms of fruit trees. They also feed on the juice of fruits.
When flying foxes need a place to rest, they roost together in the branches of large trees.
Flying foxes and other bats are the only mammals that can fly. Their wings are actually extra-long arms and fingers covered with skin that stretches to the sides of their bodies and legs. In fact, scientists classify all bats into the order Chiroptera, which comes from Greek words meaning “hand” and “wing.”
Bats that fly slowly have short, wide wings that help them make sharp turns. Bats that fly quickly have long, narrow wings.
To fly, bats stretch out their arms and fingers and pull the skin of their wings tight. They flap their wings to move through the air. They move their arms and fingers to adjust the shape of their wings to make dips, dives, and turns.
What Kinds of Sounds Do Flying Foxes Make?Flying foxes make many types of sounds. They are often very noisy—squawking and chattering while they roost.
Other bats make noises, too. They make warning calls and greeting calls to other bats. Some calls sound like honks or chirps, while others sound like hisses.
Most bats also make very high-pitched noises. These noises are so high in pitch (the highness or lowness of a sound) that humans are unable to hear them. In the 1930's, scientists were able to detect these bat noises for the first time by using special recording instruments.
How Do Flying Foxes and Other Bats See?Flying foxes have large eyes, and they can see better than most other bats. They are more active during the day than are most bats. Flying foxes use their eyesight to help them move about their habitat.
Most other bats, such as the long-eared bat, fly at night and need another way to “see” their surroundings. Instead of relying upon their eyesight, they use sounds to help them figure out where they are and where they are going. They send out their high-pitched sounds and listen to the way the sounds bounce back to them. The echoes tell the bats how near they are to other objects. This is called echolocation (EHK oh loh KAY shuhn).
What Do Flying Foxes Eat?Flying foxes belong to the family known as fruit bats. They sometimes eat nectar and pollen but, usually, flying foxes eat juice that they squeeze out of fruit. When a flying fox smells ripe fruit, it swoops down and bites into it. It then chews the fruit to a pulp and presses the pulp up against the roof of its mouth, squeezing out the juice. It swallows the juice, but spits out the fruit's pulp, skin, and seeds.
Flying foxes eat mainly such fruits as wild figs, which are not grown in orchards. But they also eat such fruits as mangoes, bananas, and papayas, and they will sometimes do a great deal of damage to orchards in which these fruits are being grown. As a result, flying foxes are considered by farmers to be pests. Compared with fruit diseases and insect pests, however, flying foxes cause very little damage to orchards.
How Do Flying Foxes Help Plants?Flying foxes have special relationships with many kinds of plants. They help spread the seeds of these plants, allowing them to grow in new areas. Flying foxes often carry the fruit they find to another place to eat. While eating this fruit, they may drop seeds on the ground. Further, the seeds they do swallow are not digested and are eliminated with their waste. The seeds end up on the ground and some of them grow into new plants.
Flying foxes also help to pollinate plants. Some flying foxes eat nectar from flowers. They then carry the pollen that gets stuck to their face from one flower to another flower. This pollinates the flowers—a process that must occur if the flower is to produce fruits and seeds.
Where Do Flying Foxes Hang Out?Like many other kinds of bats, flying foxes live together in groups called colonies. They often travel together from their roost to feeding areas. When they have eaten all the fruit in one place, they fly to other areas where there is more ripe fruit.
When flying foxes are resting, they hang upside down from the high branches of trees. Often, hundreds of bats hang next to each other on a single tree. When it is cold and raining, they fold their wings around their bodies like shawls. When it gets hot, their wings can be used like fans.
Sometimes, so many bats huddle together that they have to fight for space. Over time, the movements made as they struggle strip most of the leaves from their roosting tree.
Do Flying Foxes Ever Turn Right-side Up?Flying foxes and other bats spend a lot of their time upside down. But, they turn themselves right-side up, as well. For instance, many types of female bats are right-side up when they give birth, and bats almost always turn right-side up to get rid of waste.
Of course, when a bat flies it is right-side up and facing forward. And most bats land at their roost right-side up as well. Flying foxes are clumsy when they land, however. They look as if they are crashing into their perch. Other bats can land smoothly on their feet. They land right-side up and swing themselves upside down. Some bats are so acrobatic that they can flip themselves upside down in the air before they land on their perch.
How Do Flying Foxes Care for Their Young?Flying foxes and most other bats have one baby at a time. When it is time to give birth, the mother bats often leave their roost to go to a nursery roost.
Many types of mother bats turn themselves right-side up and hang from their thumb claws during birth. The mother catches her baby in her tail membrane, then turns upside down again and holds the newborn under her wing to nurse. Unlike many other types of bats, flying foxes often give birth while upside down and catch the young in their wings.
Infant flying foxes hang on to their mothers all the time—even when their mothers fly. After the first few weeks, though, the young are too heavy for that. Young flying foxes then hang by their claws from a branch when their mothers search for fruit.
Some other types of bats, especially those that hunt for food instead of feeding on fruit, never carry their young. They always leave their young to hang within a cave, crevice, or other hiding place.
Bat Notes
Who Has a Summer Home and a Winter Home?A type of bat known as the little brown bat can be found throughout the United States and Canada. During the summer, these bats spend the day roosting in caves, attics, or other shelters. At night, they come out to hunt for insects.
When autumn comes, little brown bats fly to their winter roosts. The winter roost may be fairly close to the summer roost. Little brown bats do not usually fly south, as do most birds and some other kinds of bats. Instead, they fly to large caves and abandoned mines, where they spend the winter. A large abandoned mine may hold up to 300,000 roosting little brown bats. Little brown bats return to the same winter homes for many generations.
Who Flies South for the Winter?Unlike the little brown bat, many other bats, including the Mexican free-tailed bat, follow migrating patterns much like those of birds. They travel hundreds of miles each spring and fall.
Most Mexican free-tailed bats spend their summers in the southern United States and in Mexico, where they roost in caves and human-made structures. They live in colonies that may include several hundred bats each. The largest colonies are made up of mothers and young.
As the days grow shorter and the weather cools, most of the adult Mexican free-tailed bats and their grown young fly to southern Mexico and Central America. Since the young are born in June, they are old enough to make the migration with their colony when it's time to leave in the fall. In spring, most of the Mexican free-tailed bats make the long trip north again.
Who Likes to Camp Out?Tent-building bats and white bats of the wet forests of Central and South America make themselves little A-frame tents in which to roost. There, they find shelter from violent rainstorms, sun, and predators.
To make their homes, these bats bite ridges into the underside of large leaves belonging to a plant called Heliconia. This plant has tough leaves that fold neatly along the ridges into a tent shape. Once they have made their tent, a group of bats gets under it and hangs on.
A single large leaf can provide shelter for over 20 bats. A colony of bats may make numerous leaf tents throughout a forest.
Who Lives in Houses?Though many people are not fond of bats, some bats do not mind living close to people. Little and big brown bats, for example, like to live indoors. They often find shelter in caves, but sometimes they live in sheds, barns, garages, or even houses. Mexican free-tailed bats roost in houses, too.
Evening bats actually seem to prefer houses—although you also can find them in tree hollows. These bats are not the only bats to live in houses. Dozens of kinds of bats find good roosting places there. Some bats are small enough to squeeze into such tiny spaces as gaps between bricks and under eaves. Any place they can go to escape predators and the weather will work.
Who Roosts Alone?Bats enjoy many different kinds of roosting places. Some bats, such as the pallid bat of the American Southwest, will hide in just about any outdoor crevice. But they will form a small colony in an indoor space, as well.
Like pallid bats, most bats are social and roost in colonies. Some, however, are more solitary and prefer to hide alone in small, outdoor spaces. The silver-haired bat often hides alone in the bark of a tree or in an abandoned woodpecker's hole. Sometimes, silver-haired bats will roost in sheds or garages, but usually only when these buildings are open or abandoned.
Red bats and hoary bats also like to be alone. Both like to rest in the thick foliage of hardwood trees. You might mistake a red bat resting alone in a tree for a dead leaf.
How Long Will Those Bats Hang There?Bats that live in cooler climates hibernate through the winter. Their heartbeat slows. Their rate of breathing lowers so much that it can seem as if they have stopped breathing. Their bodies cool to match the temperature of their shelter. They spend the winter in a deep sleep. Hibernation helps bats survive until the weather is milder and food is more plentiful.
Sometimes a bat must wake from hibernation to move from a disturbed roost or to drink water. Waking can cause a bat to use up the energy it had stored as fat for the winter. A bat that is awakened several times might not survive the winter.
In spring, when the air temperature warms up, the bat will shiver and shake itself awake. It will stretch its legs and its wings and then venture out of the cave in search of food.
Who's an Expert Bug Zapper?The little brown bat—one of the most common bats in North America—can eat more than its own body weight in insects in only one night.
The little brown bat can eat hundreds of mosquitoes a night. Its relative, the big brown bat, can eat hundreds of beetles a night.
It has been estimated that a large colony of Mexican free-tailed bats can eat over 200 tons (some 200,000 kilograms) of insects in a single night.
Although many orchard owners consider fruit bats to be pests, nearly all farmers appreciate other bats for their ability to help control insects.
Who Fishes for a Living?Fisherman bats fly over the calm lakes, rivers, and even the seacoasts of Mexico and South America in search of food. They are good at locating it, too. They can catch over 30 fish in a single night. A fisherman bat uses echolocation to sense the ripples that fish make when they approach the surface of the water. Then the bat dives down and hooks the fish using the large claws on its feet. Sometimes the bat eats its fish as it flies, but the bat may fly off to roost in a safe place to enjoy its meal.
Who Listens for the Sound of Dinner?Unlike most meat-eating bats that use echolocation to find their prey, frog-eating bats simply listen for calling frogs. When they hear frogs croaking out mating songs, the bats home in on the sound.
Frog-eating bats can tell the difference between the calls of poisonous frogs and those of harmless ones. So, they hunt for the frogs that are edible.
In addition to eating frogs, a few species of bats eat lizards, rodents, small birds, and other bats. Some bats can even catch fish with their claws. Most bats eat insects.
Do Bats Carry Rabies?Rabies is a disease that infects and kills all types of mammals. Many people think it is common for a bat to get rabies and survive it, becoming a carrier of the killer disease. But that is not quite true.
Bats rarely get rabies, but when they do, it kills them. However, a bat with rabies will usually die quietly rather than becoming obviously sick as some other mammals do. So, it is wise never to pick up a wild bat, even if it appears injured and in need of help. If frightened, the sick bat may bite and spread a disease to you.
Who Are a Bat's Predators?Because they can fly, roost in hard-to-reach places, and are nocturnal, bats are safe from most predators. And most predators will not bother with a single bat, because it is too small to make much of a meal.
But snakes, raccoons, opossums, skunks, and even tarantulas prey on bats that they find roosting in trees or crevices. Hawks and owls can sometimes catch bats in midair. A young bat that falls from its roost may be eaten by the insects that live on the floor of the cave.
Another danger faced by bats comes from parasites. Parasites are organisms that live off of other animals' bodies. For example, tiny ticks, mites, and fleas can attach themselves to a bat's body and live off its blood. Often, parasites can make a bat weak and sick.
How Do Bats Help Humans?Having insect-eating bats around can be better than having an electronic bug-zapper. In fact, humans often try to attract bats to their backyards by providing bat houses. A bat house is a small box that resembles a birdhouse, which gives bats a safe place to roost.
Bats are helpful in other ways, too. They spread seeds and pollinate plants. Even their waste, which is called guano, is useful. Bat droppings return nutrients to the soil of their habitats. Guano is even “mined” from the floor of large caves. It is then used by farmers as fertilizer.
Are Bats in Danger?Some kinds of bats are common, but others are rare or endangered. Some are already extinct. Though they do not have many natural predators, some bats are threatened by humans.
People who fear bats often destroy their habitats. Sometimes fruit growers kill fruit bats to keep them from eating their crops. Ranchers kill vampire bats to protect their livestock, too. And bats that roost in trees lose their habitats when forests are cut down.
In Asia, bats are sometimes killed for food. Even cave explorers who mean the bats no harm can accidentally disturb their roosts.
In several countries, efforts have been made to help bats survive. For example, in the United States several large caves and abandoned mines have been protected. Some of these places have been fitted with gates that keep humans out but let bats in. Several Asian flying foxes are considered endangered and are protected by international laws.
Bats make up the order Chiroptera. The fruit bats, found in the Old World, make up the suborder Megachiroptera; all other bats make up the suborder Microchiroptera.