Nature’s Bug Zappers

Bats. Just the word makes some people cringe. I remember, as a kid, ducking from swooping bats in the evening, believing they would attack me or get caught in my hair. They’re probably one of the most misunderstood and maligned animals. Despite what movies, television and literature would have you believe, bats are not terrors of the night.

Bats are incredibly important not only to our natural world but to our economy as well. As primary predators of night-flying insects, bats help to control many of our most annoying pests. A single little brown bat can catch 1,200 mosquito-sized insects in an hour. Big brown bats consume costly crop pests, including cucumber beetles, June beetles, leafhoppers, cutworm moths and corn earworm moths.

Bats in tropical areas feed on nectar, pollen and fruit. These bats, like bees, butterflies and hummingbirds, are crucial to the pollination of economically valuable plants. Some tropical bats even feed on fish or frogs, swooping over lakes searching for prey in the dark of night. The infamous vampire bat of Mexico and South America is the only species to feed on blood, mainly that of cattle or other domestic animals.

Bats are the only flying mammal. The fingers in a bat’s hand are the same as a person’s except the bat’s bones are elongated and connected by skin to form a wing. Like all mammals, bats have hair and their young are born live and feed on milk.
We often associate bats with rabies. Like all mammals, bats can contract the disease but less than one percent of bats carry it. Bats with rabies are not very aggressive and die quickly. And, like most wild animals, bats will only try to bite when handled.
Bats are not blind. Those that do hunt in the dark have developed a system to help detect objects. These bats produce sounds at high frequencies. By listening to the echoes of these sounds, bats are able to discern objects. This is known as echolocation. Using the reflected sounds, they form pictures in their brains just like we do by interpreting reflected light with our eyes.

While tropical bats are active year ’round, those in temperate regions either hibernate or migrate during the winter. Many bats hibernate in caves in winter and move to trees and buildings during summer. Some bats reside in caves all year but have different summer and winter roosts. Bats often use the same hibernation sites and summer roosts from year to year. During hibernation, a bat’s metabolism slows so that it uses very little of its stored fat. Heart rates slow drastically, and body temperatures drop dramatically. To control body temperature, bats often roost together in great numbers.

Disturbance by people is a major cause of the decline of many bat species. Bats are also threatened by loss of feeding or roosting habitat, usually wooded areas near water sources. Disturbing a maternity colony can cause mothers to drop their young or move them to a less suitable site. Disturbance during hibernation wakes bats, causing them to burn the precious fat reserves they have stored for the winter. Even responsible cave explorers can inadvertently disturb bats at critical times of the year.

Two endangered species of bats live in the Chesapeake Bay watershed, Indiana bats and Virginia big-eared bats. During summer, Indiana bats roost under tree bark along wooded streams. Females usually bear only one young in June. During the winter, Indiana bats hibernate in caves in dense clusters, averaging 300 bats per square foot. Because they mass together in winter, disturbance to one wintering cave can lead to high fatalities. The loss of streamside summer habitat stresses the population even more.

The Virginia big-eared bat, another endangered species, occupies caves during both the summer and winter. They too bear only one pup each year, are very intolerant of people, and suffer many of the same threats as Indiana bats.

Protecting these habitats is crucial to saving these species. Wooded streamside areas need to be protected for roosting. Preventing people from entering maternity caves and winter hibernation caves is critical. Since bats use these caves seasonally, entry may only have to be restricted during certain months. A cave entrance can be gated or fenced, preventing people from entering while allowing bats to fly in and out.

For more information about bats, bat houses and ways to protect bats, contact Bat Conservation International,, P.O. Box 162603, Austin, Texas, 78716, or phone 800-538-2287.

Bat Facts:
• There are roughly 1,100 different species of bats in the world, living on every continent except Antarctica.
• A colony of 150 big brown bats can protect local farmers from up to 33 million rootworms each summer.
• The 20 million Mexican free-tail bats from Bracken Cave, Texas, eat approximately 200 tons of insects nightly.
• In the wild, important foods, like bananas, mangoes, cashews, dates and figs rely on bats for pollination and seed dispersal.
• Nectar-feeding bats are the primary pollinators of giant cacti, including the famous organ pipe and saguaro cacti of the American Southwest.
• Bats occasionally fly into homes and other buildings. They will usually leave on their own if a window or door to the outside is left open while others leading to the rest of the building remain closed.

After 10 years as a biologist, Kathy Reshetiloff now writes on a variety of topics for the U.S. Fish and Wildlife Service, U.S. Department of the Interior.


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