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.