Environment and Natural Resources

Bats – Wonder Flying Machines

William N. Grafton
Wildlife Specialist
WVU Extension Service
February 2000

Bats are wonderful flying machines that can eat 1/4 to 1/3 their weight in mosquitoes each night. However,”bats in the belfry” (attic or eaves) can make enough noise, produce such stinky smells, or be such a health hazard that we don’t want them around. Let’s look at these graceful flyers that comprise 1/4 of all mammals on earth. Bats either live in large colonies or as solitary animals in West Virginia.

Bat Species: West Virginia’s most common bat is the little brown bat, which lives in colonies of several dozen up to several thousands. They live in attics, roof spaces, outbuildings, hollow trees, beneath bridges and in caves. These small bats are a rich, glossy, sleek, dark brown color. From May until September they are superb predators of numerous insects, many of which are pests to humans, pets, or farm crops and gardens.

The big brown bat also prefers attics, caves, tree cavities, etc. It is not as numerous as its smaller cousin. However, it is the bat most often encountered by humans. It often hibernates in buildings. During warm periods of late fall or early spring the big brown bat becomes active. It may fall down a chimney or find openings into our human living space. For many people this is a scary time as they try to kill the intruding bat or evict it with brooms and newspapers. Bats on ceilings or walls can be easily caught with fish nets or cardboard boxes and released outside. Another option is to open windows and outside doors, which will cause the bat to seek refuge outside the house. At nighttime lights can be turned “off” inside and “on” outside to encourage the bat to fly outside.

Big brown bats are known to eat spotted cucumber beetles, June bugs, stinkbugs and leafhoppers, all of which are destructive to crops, gardens, and landscape plants.

Solitary bats tend to spend the day in the foliage of trees, under shaggy bark, or in tree cavities and crevices. The red, silver-haired, and hoary bats are three of West Virginia’s common solitary bats. The Indiana bat (a federal endangered species) is occasionally found in hardwood forests of eastern West Virginia, where it shelters under shaggy bark or in cavities and crevices.

Natural History: Many solitary bats migrate southward for winter or hibernate in buildings and tree cavities. Bats are mammals, and their young are born from May through July. From late April until they hibernate, bats eat thousands upon thousands of mosquitoes, tree bugs, beetles, moths, flying ants, mayflies, caddis flies, etc.

Bats are experts at flying in the dark and through narrow, difficult passages. They can locate tiny insects by use of squeaking sounds that are emitted and bounce back to be picked up by their ears. This sonar system is similar to radar and is called echolocation.

Populations: Bat populations have greatly decreased over the past 50 years. Increased use of chemical pesticides to protect farm crops, gardens, lawns, and forests is a major factor in this decline. Other factors are as follows:

Human disturbance of maternity and hibernating roosts in attics, buildings, caves, etc.
Sealing and flooding of old coal mines
Forest harvesting of hollow trees
Insulating and sealing of homes to reduce energy costs.
Bat Control: Exclusion and repellents are the most common ways to control or eliminate bat populations. Exclusion involves blocking all entry/exit points to a building either before the young are born or after they are able to fly. These holes can be blocked using caulking, flashing, insulation materials, screening/wire mesh, self-expanding polyurethane foam, etc. All holes larger than 5/8” in diameter or more than 2” x 1 2” must be sealed to keep bats out.

Repellents such as napthalene (moth balls) sometimes work in airtight spaces. Lights, air drafts (fans), and ventilation are helpful and seem to discourage bats.

Bat Houses: Since bats are extremely useful, many people want bats in the neighborhood to eliminate pest insects. Bat houses offer an alternative when you force bats out of attics and outbuildings. Plans for bat houses can be obtained from the Internet or from any of the following:

Bat Conservation International
PO Box 162603
Austin TX 78716

WVU Wildlife Extension Specialist
West Virginia University
PO Box 6125
Morgantown WV 26506-6125
Phone: (304) 293-4797 Ext. 2493

Bat House Report
PO Box 67
Elkins WV 26241
Phone: (304) 367-0245

Bat houses mounted on the sides of buildings are preferred sites. Houses located on poles or trees will occasionally be used.

Health Hazards: Bats can be especially noisy and smelly on hot days. Other more serious problems can and do develop.

Cockroaches, bat bugs, ticks, mites, and fleas are common parasites around bat colonies and the associated fecal material (guano). Control of these parasites is sometimes necessary. Some people prefer to fumigate the entire space with an aerosol pyrethrum if the area is fairly airtight. Dusting the guano and roost area with boric acid powder or diatomaceous earth can also offer control. (Follow label recommendations.)

Histoplasmosis is a serious disease caused by breathing fungal mold spores that grow in dry guano or soil where the nitrogen-rich guano has dropped. Histoplasmosis can also be caused by chicken manure or starling droppings. The disease is caused by breathing airborne spores usually caused when guano or infected soil is disturbed.

Histoplasmosis is very common in the Mississippi and Ohio river drainages. It causes lesions on the lungs and general failure of the lungs. It is most damaging to young children and immunocompromised adults.

The fungus can be killed by treatment with formalin. However, this is a job for professionals because formalin is a dangerous chemical to use.

Rabies is probably the biggest fear people have of bats. Facts have shown that less than 1% of bats are infected with rabies. Bats also rank 3rd, behind raccoons and skunks, as causing humans to get rabies. To help prevent rabies, people should:

Keep vaccinations of pets up-to-date. This prevents our pets from getting rabies and spreading it to people.
Don’t mess with sick, grounded, or dead bats. Use heavy leather gloves if you must move a sick or grounded bat.
If you are bitten, seek medical advice immediately. Identify and collect the bat that bit you for medical diagnosis.
Summary: Bats are fascinating mammals. They eat many insect pests. They frequently scare people because of our fear of bats as carriers of rabies.

If we take the time to understand bats we realize that their positive values far outweigh our fears and their true health hazards.