Bats

Bats, the only mammals that truly fly, are misunderstood by many people. Their ability to fly, their secretiveness, and their nocturnal habits have contributed to bat folklore, superstition, and fear. Since bats can be both a benefit and a nuisance, this publication addresses them as both in regards to bat management. Before discussing bat management, though, it may be useful to give some explanation of their biology.

IDENTIFICATION

Bats belong to the order Chiroptera, meaning "hand-winged." A bat's forearms and hands are modified into large wings by a membranous skin that is stretched between the bones. Sixteen species of bats are found in Georgia. Two of these species, the Gray Myotis and the Indiana Myotis, are listed as endangered species by the U.S. Department of the Interior.

BAT SPECIES: Family Verpertilionidae                  BAT SPECIES: Family Molossidae

 

COMMON NAME	SCIENTIFIC NAME
Little Brown Myotis	Myotis lucifugus
Southeastern Myotis	Myotis austroriparius
Gray Myotis	Myotis grisescens
Indiana Myotis	Myotis sodalis
Eastern Small-footed Myotis	Myotis leibii
Northern Myotis	Myotis septentrionalis
Silver-haired Bat	Lasionycteris noctivagans
Eastern Pipistrelle	Pipistrellus subflavus
Big Brown Bat	Eptesicus fuscus
Red Bat	Lasiurus borealis
Seminole Bat	Lasiurus seminolus
Hoary Bat	Lasiurus cinereus
Northern Yellow Bat	Lasiurus intermedius
Evening Bat	Nycticeius humeralis
Rafinesque's Big-eared Bat	Plecotus rafinesquii

COMMON NAME	SCIENTIFIC NAME
Brazilian Free-tailed Bat	Tadarida brasiliensis

 

 

 

 

 

 

 

 

 

 

 

 

(*Those in red are considered Endangered Species)

Bats can range in size from 8 - 13 cm (about 3 – 5 in.) total length. Their color varies from dark yellowish or silver markings, grayish brown to grayish black, depending on the species. Click here for a detailed picture of a bat’s features.

HABITAT AND BEHAVIOR

Bats “roost” during the day and feed at night. The natural habitats for bats in Georgia are include forests, wetlands, or caves. However, attics, eaves, and chimneys sometimes make ideal roosting areas for bats. Bats use many different sites for summer roosts, including caves, old mine shafts, buildings, hollow trees, the area beneath sheets of loose tree bark, rock crevices, and cliff faces. Some species are very particular about their roosting site and use only one or two kinds of summer roosts. Bats hibernate in the winter and may travel as far as 482.8 km (300 mi) to get to their winter roost, which is usually a cave or abandoned structure.

Breeding generally takes place in late autumn. This would explain an increased number of sightings of bats at this time of year. In May or June of the following spring, 1 - 2 young (depending on the species) are born. In some species, females gather together to form a "maternity colony" of up to several hundred individuals, and remain together until August or September when the young are able to fend for themselves. The young are able to fly within 3 - 5 weeks after birth. Sexual maturity is reached in 1 - 2 years, depending on species. The Little Brown Myotis can live for 30 years. This is the longest life span known for a bat.

Since most bats are insectivorous, the flying insects that congregate around streetlights provide a ready source of food. Their diet is composed mostly of mayflies, midges, flies, moths, beetles, and mosquitoes. Bats locate these flying insects by using a built-in sonar system that detects objects through echolocation. Echolocation is the use of high frequency sound like sonar and radar by animals (i.e. whales and bats) to locate objects in the surrounding environment and to avoid collisions with obstacles.

NUISANCE IDENTIFICATION AND CONCERNS

Bats are quite adept at catching insects, possibly as many as 3,000 each night. Despite these beneficial qualities, bats may become a nuisance if they take up residence in a manmade structure.

People tend to immediately blame any rustling sounds in their chimney or attic on bats. In actuality, the culprits may be squirrels, rats, or chimney swifts.  Consequently, before implementing any control measures, first determine whether bats are the problem. Outside buildings, bats may roost behind shutters, under shingles or roofing, or in any other place that provides protection. One thing to look for is “bat droppings”. Bat droppings are easily distinguished from rodent droppings when they are crushed. Bat droppings contain shiny bits of undigested insects and never contain a white, chalky substance. Another sign of the presence of bats is a brown stain around entrance holes on the exterior of a building. This stain is left by oils from the bat’s body.

The health hazard posed by bats has been greatly exaggerated. From 1953 to 1998, 35 human rabies fatalities have been attributed to bats. Data on the frequency of rabies in bats is misleading because it reflects only sick animals in laboratories and not random population samples. Far more people die annually from dog attacks, bee stings, lightning, and household accidents than from bat-transmitted rabies. However, any bat bite should be treated as a potential rabies infection, and medical attention should be sought.

Another concern related to bats is histoplasmosisis, which is an airborne disease from a fungus that grows in soils enriched with bird and bat droppings. While the potential dangers of contracting histoplasmosis are slim, guano should be moistened with water before it is removed. This reduces the amount of dust that may become airborne. Bat guano (feces) and urine accumulating in attics may attract insects, and while the odor may not be pleasing, it is not dangerous.

MANAGEMENT OPTIONS

The presence of a bat colony is fairly uncommon—more common is the occurrence of one or two wayward bats in a house. The simplest solution for this type of bat problem is to open all the doors and windows. Bats usually detect the fresh air and leave. If the bat is still there at night, turn off the lights to help it find the doors and windows. Bats normally will not attack people and can be caught in a net, box, can, or a gloved hand. The captive bat can then be released outside. However, bats will bite when handled, so exercise caution.

People often think that bats are swooping at or attacking them; however, most bats are merely searching for insects. Bats may fly around swimming pools to drink and to catch insects. Any outside lights that attract flying insects may also attract bats. Both of these situations may bring bats into closer proximity with people.

Exclusion

The long-term solution to any bat problem is to exclude the bats from the area. Bats can enter a building through tiny holes, so a careful inspection must be made to block all entrances. When trying to bat-proof the interior of a house, check for air leaks that may reveal possible points of entry. One simple way to find air leaks is to hang a thin plastic bag or tissue paper from a coat hanger and place it near a windowsill. The plastic or tissue will move or wave if air is leaking through. A lighted candle can be used in a similar way—the flame will flicker and move if air currents are present. Make sure the bats are out of the building before bat-proofing it. This means doing the work at night or installing a one-way valve. One-way valves should be installed over all major entry points, with at least one valve on each side of the building the bats are using.

One-way valves can be constructed from a 6- to 8-inch length of 2-inch-diameter pipe and a 6-inch piece of plastic drop cloth rolled into a tube and taped to one end of the pipe. The bats will exit the building but will be unable to return via the one-way valve. One-way valves should not be used from May through August when flightless young are present.

 

 

Repellents

Bats can be repelled from an area for short periods of time. Floodlights or some other method of illumination in the attic may repel bats. This technique can also be useful in locating entrance/exit holes from the outside. Simply turn on the light in the attic, go outside at night, and look for the rays of light coming out of the attic. Mark the spots, and then patch them. Bats do not like to colonize areas with a lot of air movement. Drafts created by fans or open windows may be effective in repelling bats.

Chemicals

Toxicants and fumigants are not recommended in Georgia because of the protected status of bats. In addition, the dead bodies of poisoned bats and other organisms may attract even more serious pests. Buildings must be bat-proofed after the bats are trapped or repelled; otherwise, bats will be a persistent problem.

LIVING WITH BATS

The beneficial aspects of bats make them enjoyable to have around. Bats may be encouraged to take up residence in an area if bat houses are provided. This practice, similar to that of putting up bluebird boxes, provides roosting sites for bats. Be sure that the crevice widths for the bats are 3/4 inch wide. Use rough lumber so the bats can climb out easily and staple plastic mesh to interior surfaces to provide secure footing for the bats. Exterior-grade plywood is best for the front, back, and partitions. Solid wood is best for the sides and roof. Bat houses should be at least 16 inches wide and 30 inches tall.

The finished box should be placed in a sunny area about 12 to 15 feet off the ground. The side of a building or a pole makes a good site. Placing the bat box within 1.4 mile of an open, permanent water source such as a pond or river increases the chance of occupation. Areas with high insect populations, a mixture of natural vegetation and agriculture, and areas where bats are already attempting to live in buildings are also good bat house locations.

 

SOURCES

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln

Georgia Wildlife Web http://naturalhistory.uga.edu/gawildlife/mammals/chiroptera/verpertilionidae/efuscus.html