Bat

There are more than 900 species of bats. Bats live in all parts of the world except Antarctica and the Arctic. Most kinds make their home in the tropics, where they can find food the year around. About 40 species of bats live in Canada and the United States.

Through the centuries, people have passed on many superstitions and mistaken ideas about bats. For example, the expression "blind as a bat" is false. All species of bats can see, probably about as well as human beings. The beliefs that bats carry bedbugs and get tangled in people's hair are also untrue. Bats tend to be timid. At night, they will try to fly out a window if they find themselves in a room.

Many people in Western countries fear bats, but these animals are well liked in China and Japan. A number of Oriental artists have portrayed bats as signs of good luck, happiness, and long life.

Most bats are harmless to people. But bats may have rabies. For this reason, bats should not be handled.

Bats perform a valuable service for people by eating large numbers of insects. In addition, bat guano (manure) has commercial value as fertilizer. Some caves have been the home of bats since prehistoric times and have large deposits of guano.

The largest bats, called flying foxes, have a wingspan of more than 5 feet (1.5 meters) and a body about the size of a pigeon's. The Kitti's hog-nosed bat of Thailand, the smallest species, is about the size of a bumble bee and weighs only about 1/14 ounce (2 grams). It is one of the smallest known mammals in the world. Many common North American bats have a wingspan of about 12 inches (30 centimeters) and weigh from 1/6 to 2/3 ounce (5 to 19 grams).

The skeleton of a bat resembles that of other mammals. Like many other mammals, a bat has hands with fingers and feet with toes. A bat's breathing rate, heartbeat, and body temperature, unlike those of many other mammals, vary greatly, depending on its activities and the temperature of its surroundings. Among some species, the temperature of a resting bat becomes the same as that of its environment.

Head. The face and head of bats vary greatly among the various species. Some bats have a head shaped like that of a miniature bear or dog. Other bats have a flatter face. Some species have folds of skin called a nose-leaf on their snout. The nose-leaf may look like a spearhead or a blade. Bats have a good sense of smell that helps them find food and their roost.

Most bats have small, sharp teeth that reduce food to a soupy texture. Bats digest their food more quickly than many other mammals. This rapid digestion helps them avoid having extra weight while flying.

Wings and legs. A bat's hands serve as its wings. Its long fingers support the flexible skin of the wings. The upper arm, forearm, and second and third fingers make up the front edge of the wing. The fourth and fifth fingers help support the wing. The inner edge of the wing extends down the side of the body and along the leg to the ankle and foot.

The length of a bat's wings varies from species to species. The swiftest species of bats have long, narrow wings. Some species, which can hover in one place, have short, broad wings. Some bats can fly as fast as 15 miles (24 kilometers) per hour, but most of them travel from 5 to 8 miles (8 to 13 kilometers) per hour.

Bats have weak legs. Many species have a tail and a membrane between their legs. Some fold up their wings and use their arms and legs to walk. But a number of species do not walk at all. They use their legs simply to hang from their roost. Each foot has five toes with semicircular pointed claws that enable the animal to hang securely from twigs and rocks.

About an hour before dusk, bats start to move around or take short flights. At dusk, they begin to fly from their roost and head for their feeding grounds. Many species eat insects, and each species seeks its own kind of feeding area. Some bats feed in open areas. Other kinds feed in heavy jungles or above a pond.

Many bats eat as much as half their weight in food each night. They then rest in either their daytime roost or a different night roost. After digesting their meal, they may eat again. Sometime before dawn, they return to their daytime roost in order to sleep.

Bats have few enemies. Such animals as cats, hawks, owls, snakes, and weasels sometimes prey on bats. Bats avoid many enemies on the ground by hanging from high places. Some species of bats live as long as 15 to 25 years.

How bats navigate. Some bats depend on their vision and sense of smell to navigate and to find food at night. Other bats cannot see well in the dark. They navigate by means of echoes. These echoes result from a series of short, high-frequency sounds that the bats make continually while flying. From these echoes, the animals can determine the direction and distance of objects in the area. This process of navigating is referred to as echolocation. Each species of bat that uses echolocation makes its own kind of noises. Most of these sounds extend beyond the range of human hearing. Some zoologists believe that a bat may use its lips or nose-leaf to direct the sounds in a particular direction or at a specific target, such as an insect. Echoes from the insect give the bat information about the movement of the prey, in addition to its direction and distance.

Food. Many species of bats feed on insects that fly at night. A bat catches insects in its mouth, tail membrane, or wings as it flies.

Numerous species of bats prey on large insects, scorpions, or spiders on the ground. Other bats pluck insects from the surface of water with their mouth or claws. Some bats catch fish with their claws, and a few species eat lizards, rodents, small birds, tree frogs, and other bats. The vampire bat feeds on the blood of other animals.

Several kinds of tropical bats feed on plants. Some of these species gather nectar and pollen from flowers. Such bats pollinate the plants on which they feed. Other tropical bats eat fruit and thus help spread the seeds of many plants. These bats may drop small seeds from their mouth as they eat at their feeding ground. They also may bring fruit with large seeds to their roost and drop the seeds there after eating the fruit. Seeds also are deposited with the bats' guano. The seeds may land on soil and sprout.

Bats that eat moist foods do not need to drink much water. Many species of bats lap up water with their tongue as they fly near the surface of a pond or stream.

Hibernation and migration. Many bats hibernate or migrate during the winter because of low temperatures and a poor food supply. Insects and plant foods become scarce in winter. Most North American bats hibernate in caves or rocky places. While hibernating, they live off the extra fat that they gain during the late summer.

Some North American bats migrate in the fall to find food or a better place to hibernate. They may fly long distances to find a suitable shelter that will protect them from the harsh winter weather. Most cave bats spend each winter in the same place, and each summer in the same roost.

Bats of the tropics do not hibernate. The temperature and food supply there remain suitable all year. Scientists know little about the migration of tropical bats.

Reproduction. Among many species of bats, the males and females occupy different roosts. The males and females of some species even live in different regions of a continent except during the mating season. The mating season, which lasts for only a few weeks, may occur during the spring, fall, or winter, depending on the species. The female may carry the male's sperm within her body for several months before she becomes pregnant. In the spring, pregnant bats may leave their usual colony and join together in a nursery colony, where they give birth and rear their young.

The females of most species of bats have one baby a year. Some bats have a baby twice a year. A few species have up to four young at a time.

A newborn bat weighs about a fifth as much as an adult bat. Bats do not build nests, and so the infant must hold on to its mother or its home roost. Among some species, the infant clings to the mother for several weeks. The infants of other species stay in their roost, where they hang from a rock alone or with a group. Female bats nurse their young for six to eight weeks.

Flying foxes and similar species known as fruit bats live in most tropical regions of Africa and Asia. These bats eat mostly fruit and occasionally damage orchards. Flying foxes also eat flower buds, nectar, and pollen. Flying foxes have large eyes and better vision than many other bats.

Vampire bats include a few kinds of bats that feed on the blood of other animals. The common vampire bat lives in Central and South America. It weighs about 1 ounce (28 grams) and has a wingspan of about 12 inches (30 centimeters). It preys mainly on cattle. It sometimes bites human beings, but such incidents are rare. Vampire bats approach their prey on foot. They scoop out a small piece of the victim's skin with their sharp teeth and then lick blood from the wound. Vampire bats consume about 1 tablespoon (15 milliliters) of blood a day. The wound they give their victims heals quickly, but these bats may carry rabies.

Brown bats include the big brown bat and the little brown bat, both of which live in the United States. Brown bats live in buildings or caves, and some migrate before they hibernate in winter. The big brown bat has dark brown fur and a wingspan of about 12 inches (30 centimeters). The little brown bat has dark brown fur and black forearms and ears. Its wingspan measures about 8 inches (20 centimeters).

Free-tailed bats are a group of dark brown bats that live throughout the world. Their tail extends beyond the tail membrane. A few kinds of free-tailed bats, especially the Mexican free-tailed bat, can be found in the Southern United States. The Mexican free-tailed bat has large ears, sharp teeth, and a wingspan of up to 12 inches (30 centimeters). Mexican free-tailed bats live in colonies, mostly in caves.

The hoary bat, the largest bat of North America, has a wingspan of about 16 inches (41 centimeters). White hairs cover its reddish-brown underfur, giving the bat a spotted appearance. Hoary bats live alone in trees and migrate south for the winter.

The red bat has white-tipped red fur. The male is bright red, and the female is grayish-red. Red bats have short, rounded ears covered with fur. Their wingspan measures about 12 inches (30 centimeters). They live alone in trees and fly south every winter.

The silver-haired bat has dark underfur with white outer hair. Both males and females have brownish underfur, but the male has blacker coloring. The silver-haired bat has a wingspan of about 13 inches (33 centimeters). It lives in trees. In summer, the males live alone, and the females in groups. Some hibernate in winter, but most migrate south.

Scientific Classification. Bats make up the order Chiroptera in the class Mammalia and the phylum Chordata. Flying foxes and their relatives make up the suborder Megachiroptera; all other bats belong to the suborder Microchiroptera.

Contributor: Clyde Jones, Ph.D., Prof. of Biological Sciences, Texas Tech Univ.

Halton, Cheryl M. Those Amazing Bats. Dillon Pr., 1991. For younger readers.

Hill, John E., and Smith, J. D. Bats: A Natural History. Univ. of Texas Pr., 1984.

Pringle, Laurence P. Batman: Exploring the World of Bats. Scribner, 1991. For younger readers. Describes the life and work of Merlin Tuttle, a noted mammalogist.

Tuttle, Merlin D. America's Neighborhood Bats. Univ. of Texas Pr., 1988

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