When your Nuisance Animal is a Bat...

Bat control should be done by excluding entry into buildings, not by killing bats.

Some people wrongly believe bats are flying mice. In fact, bats form a separate and distinguishable group of mammals more closely related to moles, shrews, and even monkeys than to rodents. Bats are the only flying mammals, and, except for certain unique features, their anatomy is similar to that of most other mammals.

Bat's wings are very different from those of birds, and built upon the same general pattern as the limbs of other mammals. The wing is composed of an upper arm, forearm, wrist, and hand with thumb and four fingers. The hand and fingers are greatly elongated in order to spread and control the wing. The hind limbs of the bat are attached at the hip in reverse, pointing the knees backward. This arrangement is thought to facilitate the bat's ability to alight upside down and hang by its toes.

Bats occur worldwide. Of the approximately 850 species of bats only 39 occur in the United States and of those, 17 occur in Florida. (For details on specific species see "A Checklist of Florida's Mammals", Florida Game and Fresh Water Fish Commission (GFC).)

Taxa	Florida Range	Abundance	Roosting Habitat	Comments
Twilight Bats
Big brown bat (eptesicus fuscus)	Statewide except Keys	Rare	Caves, trees, buildings	Roost near entrance
Silver-haired bat (Lasionycteris noctivagans)	Panhandle	Rare	Trees	Migratory species
Red bat (Lasiurus borealis)	Northern 1/2	Common	Trees	Sexually dimorphic, females less colorful
Hoary bat (Lasiurus cinereus)	Northern 1/3	Uncommon	Trees	Large bat, white-tipped fur
Northern yellow bat (Lasiurus intermedius)	Statewide except Keys	Common	Trees, palm fronds	Very common in southern Florida
Seminole bat (Lasiurus seminolus)	Statewide except Keys	Common	Trees, Spanish moss	Southeastern species named for Seminole Indians
Southeastern bat (Myotis austroriparius)	Northern 2/3	Abundant	Caves, trees, buildings	Large mixed-species maternity colonies
Gray bat (Myotis grisescens)	Panhandle	Rare Endangered	Caves, year-round	Endangered by loss of cave habitit
Little brown bat (Myotis lucifugus)	Northern border	Few records	Caves, buildings	Probably do not reproduce in Florida
Northern long-eared bat (myotis septentrionalis)	Panhandle	Few records, Endangered	Caves, trees, buildings	Probably do not reproduce in Florida
Indiana bat (Myotis sodalis)	Panhandle	Few records, Endangered	Caves, trees	Summer migrant
Evening bat (Nycticeius humeralis)	Statewide except Keys	Common	Trees, buildings	Residents joined by northern migrants
Eastern Pipistrelle bat (Pipistrellus subflavus)	Statewide except Keys	Common	Caves, trees	Florida's smallest bat
Rafinessque's big-eared bat (Corynorhinus rafinesquii)	Northern 3/4	Uncommon	Trees, buildings	Prefers cypress tree cavities
Free-tailed Bats
Florida wagner's mastiff bat (Eumops glaucinus floridanus)	Southern 1/4	Rare: State Endangered	Tree hollows, buildings	Florida's largest bat
Little mastiff bat (Molossus molossus)	Keys	Rare	Buildings	Tropical species
Brazilian fee-tailed bat (Tadarida brasiliensis)	Statewide except Keys	Common	Buildings, trees	Live in colonies year round
New World Fruit/leaf-nosed Bats
Jamaican fruit bat (Artibeus jamaicensis)	Lower Keys	Few records	Trees	Florida's only fruit eater, prefers figs
This table comes from Fact Sheet WEC 186, one of a series of the Department of Wildlife Ecology & Conservation, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: October 2004. Please visit the Edis Web site at http://edis.ifas.ufl.edu.

Florida bats are highly beneficial because they consume tremendous numbers of night-flying insects, including mosquitoes. Bats locate insects at night using a very sophisticated sonar system (echolocation), emitting supersonic sounds and listening for echoes. Bats are most frequently seen on warm nights feeding over bodies of water, around buildings or forest edges, or around lights. During the day, bats find shelter in a variety of secluded places, preferring small, dark, poorly ventilated spaces that heat up during the day. Tree cavities, snags, and especially unpruned cabbage palms are important roost sites. Due to increasing urbanization, the number of these natural roosting sites has been reduced and window shutters, drain pipes, billboards, roof tiles, and attics have become popular roosting site substitutes.

Bats in the home

If the bat "disappears" in the room, it probably has landed behind a curtain or in some hidden nook. In this case: open a window, turn off the lights, close the door behind you, and isolate the bat by blocking the space under the door with a towel. The bat should find its way out within an hour after dark as long as the weather is not too cold. One or two bats in the home may mean only that they came in through an open window. However, their presence could be a sign that a colony of bats has established a roost in a crawl space or attic. An obvious sign that a bat colony has taken up residence is when bats are observed flying in and out of a hole in the house. If they become a nuisance, the only long-term solution is to bat proof the building ( Figure 1) .

Bat Control Methods

Exclusion Method

To remove a bat colony, locate where the bats are entering or exiting. Since bats leave their roost shortly after sunset, watch the outside of the house from 30 minutes before sunset until 30 minutes after. Bats may enter and exit through an unscreened attic vent, a chimney, and cracks or openings along eaves, window sills, and siding. Note: Bats do not need an opening they can fly through. A crack only 3/8" wide will admit bats.

Once all entrances have been located, seal all but the primary entrance. Next install a one-way door over the entrance as shown in Figure 1 . Wait three or four nights, and if bats are no longer seen leaving the building, seal the remaining hole. If all the holes have been sealed, there will be no further problems.

Cracks, separations, or other openings should be repaired as soon as they are noticed. Keeping the house weather-tight and energy efficient is the best way to prevent bat problems from recurring.

Methods of habitat manipulation

Since bats prefer dark spaces, artificial light can be used quite successfully, but only if the light is kept on continuously and moved regularly. Otherwise, the bats will soon find dark corners to avoid the light. This method also may cause bats to move deeper into the house as they avoid the light, making them more likely to enter living areas and come into contact with people.

Repellents

Although a number of methods have been devised to repel bats, this approach is only a temporary solution. Naphthalene (mothball) flakes can be applied to the area of infestation. As long as a strong odor remains, bats may not return. The effects will not last long and repeated applications are required to deter bat re-entry. Ammonia can be used to clean areas infested by bats. Pans of the solution then can be placed in a former roost to act as a repellent. Neither of these methods will be successful as long as bats can reenter the habitat once the odor has begun to fade. The strong odor is also offensive to humans and repeated applications may not be a tolerable long-term solution. Repellents are not as effective as simply waiting for the bat's normal departure at dusk and taking appropriate exclusionary measures.

Fumigants

There are serious disadvantages to the use of fumigants against bats. The results are not permanent, and the building may be recolonized at a later time. Also, poisons used in the extermination of bats may cause an increase in human or pet contact with bats as sickened bats fall to the ground and slowly die. Even if fumigation quickly killed all bats present, it would provide only a very temporary solution at best. Other bats could safely move in within just 2 days unless entry holes are plugged--a solution that would negate the need for fumigation. If fumigation killed a significant number of bats within the walls of a home, a serious odor problem would result. Simple exclusion after the bats' nightly departure is a far preferable solution.

A fumigant can be considered for bat control only in a real public health emergency under the authority of a special permit issued by the Florida Game and Fresh Water Fish Commission and only after all other feasible methods of exclusion and removal have failed.

Ultrasonics Ultrasonic repellents are ineffective as a deterrent against an animal that uses ultrasound waves in many aspects of its life. They may actually attract bats.

Credits

This document is WEC32, one of a series of the Wildlife Ecology and Conservation Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date June, 1991. Revised September, 2002. Reviewed September, 2002. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.
Authors: Amy K. Taylor, former undergraduate assistant; Frank J. Mazzotti, Ph.D., associate professor, Wildlife Ecology and Conservation department, University of Florida, Everglades REC, Belle Glade, FL 33430, and Craig N. Huegel, former assistant extension scientist, Pinellas County, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611.
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