The Life of a Bat. How Bats Navigate

The life of a bat. Many species of bats live in colonies that may have thousands or even millions of members. Others live alone or in small groups. Most bats spend the day sleeping in their roost. They also may groom their fur and wings or tend their young during the day.

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.

Roosting bats hang upside down. Most bats spend the daylight hours resting in this position. Flying foxes, above, usually roost in trees. Many kinds of bats roost In caves and In buildings

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.