For Specific Issues


QUESTION: If I install a bat house, will the bats move into it AND leave my house?

ANSWER: Bat houses are excellent management tools that can provide displaced bats with a safe alternate roost away from structures where they are unwelcome. And while it is true that bats in a bat house are not in your house, bats are faithful to their homes, and very rarely voluntarily leave an active roost for a bat house.

Even the most well-planned and humanely-intentioned bat exclusion means habitatloss and displacement for bats. For that reason, when an exclusion is planned, BCI recommends installing one or more bat houses nearby, well in advance. Learn more by visiting our bat house page

QUESTION: How can I get bats to leave and not come back?

ANSWER: When bats roosting in a structure are unwelcome, exclusion is the only permanent solution. The objective should be to get all bats safely out of a building and to keep them out permanently. Although projects can vary in scale depending on structure type, species present and roost location, the process is the same regardless of the number of bats or how long they’ve been there. A complete description of the bat exclusion process can be found here.

QUESTION: What if I find a bat (or a colony) out in the open?

ANSWER: Bats are sometimes found alone or in large numbers roosting on the exterior of structures, or in open structures like parking garages. These are usually temporary stopovers, sometimes during fall and spring migration. Left alone, these bats will usually continue on their way within a few days or weeks.

QUESTION: What if you WANT bats in your attic?

ANSWER: Each year, BCI staff field hundreds of inquiries about excluding bats from buildings. Occasionally, however, we get a call from somebody wanting to increase the numbers of bats in their building! Often these are abandoned buildings used for interpretive purposes, structures housing endangered or threatened species, or buildings owned by people who simply realize that the benefits of bat residents can outweigh drawbacks. See our bat house page where we have re-posted the archive of Bat House Research Project newsletters we published during our 10-year research project, for ways to accommodate more bats, while minimizing problems from guano or noise.

QUESTION: How I can discourage bats from roosting on my porch?

ANSWER: Some species such as pallid bats (Antrozous pallidus) use open porches, patios, or garages as temporary night roosts for feeding or social activity. Bats are usually absent from these sites during the day, and insect parts or guano may be the only evidence that bats were roosting the night before. These night roosting bats can be discouraged by making their roosting area ‘less comfortable’ by adding clutter or making roosting surfaces difficult to hang on.

Bat Roosting Deterrents (To be employed only when bats are NOT present)

  • Mylar Balloons floating near the roost
  • Strips of mylar material or even tin foil tacked up at the roost so they move in the breeze
  • Curling ribbon (long pieces, curled and tacked at the roost)
  • Plastic taped over the roosting spot (to make it too slick for their feet to hold on and hang there)
  • Bright lights and fans


These ideas are intended for night roosting bats (i.e., bats roosting under eaves of a roof or on a porch, etc., digesting the insects they have eaten), and the idea is for the bats to develop new habits. Day-roosting bats are usually in nooks, crannies, and crevices and must be properly excluded.

QUESTION: What if I find a bat in my patio umbrella?

ANSWER: Some bat species, including tri-colored bats, evening bats and southeastern myotis, find the crevice-like folds of a closed patio umbrella to be a perfect day or night roost. These are often transient solitary bats , but small maternity groups of Evening bats have been observed in early summer. If mothers and pups are present, they should be left undisturbed until pups are flying on their own. Then, if the bats are not welcome, the umbrella can be carefully opened after the bats leave at night and left partially open to discourage roosting.

QUESTION: Are bats dangerous?

ANSWER: Bats do not attack people, and reports that they do are usually related to incidents where bats fly near people in swimming pools as they swoop in for a drink, or near people outdoors in the summertime, when insects are abundant around us; bats DO attack insects! However, bats, along with several other mammal species, are a “rabies vector” species. That means that there will always be incidences of the rabies virus in bat populations. However, bats do not “carry” rabies. The vast majority of bats do not become rabid and there is no evidence of epidemic outbreaks in bat colonies. That is because when bats become infected with rabies, they die from the disease. Rabies can only be contracted if the virus enters the nervous system through a bite wound or mucous membranes (eyes, mouth or nasal passages). The virus is not spread through contact with blood, urine or droppings (guano), but through contact with saliva or central nervous system tissue. The virus is almost always contracted by way of a bite from a rabid animal.

CREDIT: J. Scott Altenbach

QUESTION: What is an ‘undetected’ bat bite?

ANSWER: Many people believe that it is common to be bitten by a bat and not feel it. Though it is not impossible for that to happen under unusual circumstances, most professionals who handle bats on a regular basis will tell you that bat bites hurt. Bats have small, sharp teeth made for biting through insect parts and a bite from an insectivorous bat feels very much like a needle jab. However, because those teeth are small and sharp, a bat bite might not bleed and might not leave a very noticeable mark on human skin.

QUESTION: Is bat guano harmful to my family?

ANSWER: Histoplasmosis is a respiratory disease caused by a fungus that grows in soil enriched by animal droppings, including those from bats. Ninety percent of all reported cases in humans come from the Ohio and Mississippi River valleys and adjacent areas where warm, humid conditions favor fungal growth. The disease is rare or nonexistent in most of Canada and in the far northern and western United States. The majority of cases are asymptomatic or involve flu-like symptoms, though some individuals, primarily those who are immune-compromised, become seriously ill, especially if exposed to large quantities of spore-laden dust. To be safe, avoid breathing dust in areas where there are animal droppings; if you must clean an area of bat or bird droppings, wear a respirator that can guard against particles as small as two microns.

The U.S. Centers for Disease Control and Prevention provides information about Histoplasmosis here.

Excluding a Colony

Excluding bats from buildings—How to do it

Removing, or excluding, bats from buildings requires establishing one-way exits through which the bats can leave but cannot return, while also sealing all other potential entry points. This process of eviction and exclusion is the only effective and permanent solution when bats in a building are unwanted.

Trapping and relocating is ineffective since bats have powerful homing instincts and will simply return, even when released at great distances. The use of pesticides against bats is illegal and counterproductive, and greatly increases the likelihood of bats coming into contact with people and pets. Naphthalene, the active ingredient in mothballs, and ultrasonic devices are often promoted as bat repellents. Ultrasonic devices have proven ineffective, however, and naphthalene, to be effective, would have to be used in such large quantities that it would pose a significant health hazard to humans.

How to Exclude Bats:

Excluding bats with tubes

In most cases, tubes make the best bat-exclusion devices. These include openings on buildings with rough exterior walls, such as brick or stone houses and log cabins. Tubes also work best for holes at corners where walls meet and on horizontal surfaces such as soffits.

Catching bat with box

Exclusion tubes should have a diameter of two inches (five centimeters) and be about 10 inches (25.4 centimeters) in length. Exclusion devices can be purchased commercially or made from PVC pipe or flexible plastic tubing. Bats are unable to cling to the smooth surface of these tubes, so the tube should project no more thanone-quarter inch (six millimeters) into the opening.

This will ensure exiting bats can easily enter the tube. Empty caulking tubes also work well after caps at both ends have been cut away. Caulking tubes must be thoroughly cleaned before they can be used for exclusions because dried caulk forms a rough surface that could allow bats to reenter. These flexible, plastic tubes let you squeeze one end so it fits into a crevice. Or you can cut one end into flaps that fit over an opening and can be caulked, stapled, nailed or screwed into place (see diagram).

Once the tube has been secured over the hole, a piece of lightweight, clear plastic can be taped around the tube’s outside end (see diagram) to further reduce the likelihood of bats reentering, though this is usually not necessary.

Catching bat with box

After the tube has been secured into or over an opening used by bats, any spaces between the outer rim of the tube and the building must be sealed shut. Also be sure to seal any other openings in the building that bats could use. Leave the tube in place for a minimum of seven days to ensure all bats have left. After the bats have been excluded, the tube should be removed and the opening permanently sealed with water-based silicone caulking, caulk-backing rod, hardware cloth or heavy-duty plastic mesh. In some cases, sealing may require repair or replacement of old, deteriorated wood. When bats are using multiple openings to enter and exit, exclusion devices should be placed on each opening. If the bats do not appear to be exiting or seem to be having trouble doing so, add new valves as needed.

Never simply wait for bats to fly out at night and then seal openings. Not all of the bats leave at the same time, and some may remain inside all night, especially during storms.

Keep in Mind:

Catching bat with box

Seasonal Concerns

Bats often roost in buildings during maternity periods, when they give birth and raise their pups. Exclusions should not take place until young bats are able to fly; otherwise, they will be trapped inside, away from their mothers, and die of starvation. Separating pups from their mothers may also lead mother bats to search for other entrances to reach their young. In North America, the maternity season begins as early as mid-April in the southernmost United States and in the mid-June in the northern U.S. andCanada. Young bats are usually flying by late August.

Exclusions should not be conducted between April and late August.

Cool or Severe Weather

Catching bat with box

Contrary to popular belief, not all house-dwellingbats migrate to warmer climates or enter caves or abandoned mines to hibernate in the late fall. However, a few species can hibernate in buildings. If hibernating bats are present in cold regions during the winter, exclusions should be postponed until spring when they emerge to feed. In mild climates, some bats may remain active year-round, but exclusions should be carefully monitored or avoided during cool weather when night-flying insects are not present, and at any time of year when rain, wind or severe weather is occurring or expected.

When bat exclusion should not be performed

Bat exclusion should NEVER be performed during any period when bats do not leave their roost on a regular nightly basis. This includes during maternity season in the summer, hibernation or torpor (a less lengthy period of inactivity) in winter and during periods of inclement weather. Maternity season dates vary by region and are species-specific; though not typical, some tropical and subtropical species in southern regions may give birth twice a year.

In North America, the maternity season begins as early as mid-April in the southernmost United States and in mid-Junein the northern U.S. and Canada. Young bats are usually flying by late August. Exclusions should not be conducted between April and late August. Some U.S. states and Canadian provinces have passed regulations governing bat exclusion dates. Please check with your state or provincial wildlife agency for the rules in your area.

Methods to Avoid:

Methods that pose a danger to bats or the public and are NOT recommended:

  • Any products or structural modifications that block natural ventilation, like hanging plastic sheeting over an active roost entrance, thereby altering roost microclimate
  • Silicone, polyurethane or similar non-water-based caulk products
  • The use of flexible netting as an exclusion device, or one-way door, is overly complicated and there are multiple draw-backs, including entangling bats, which can result in permanent injury or death. In the majority of situations, BCI does not recommend its use.
  • Any exclusion device attached with duct tape. Duct tape or similar adhesive tapes fail when surfaces are rough, coated with dust, mold or mildew, or when used in high humidity or during rain, and can result in re-entry or entrapment.
  • Expandable foam can block ventilation and break down in the heat, allowing bats to re-enter. It can kill bats that are exposed to the material before it dries--dead bats have been found entombed in foam.

Hiring a Professional:

Should I Hire a Professional or Do it Myself?

Safely and permanently excluding bats from buildings requires patience and attention to detail. It can involve working high on ladders, scaffolding or even a hydraulic lift. Though detailed exclusion instructions are included here, many prefer to contact a bat management professional. Bat Conservation International no longer maintains a list of BCI-approved bat exclusion professionals, but we do provide criteria for selecting a qualified professional.

BCI recommends that the company:

  • Have verifiable bat exclusion experience (both the company and the individual)?
  • Be licensed by the state and insured against any incidental damage that may occur?
  • Have demonstrated knowledge and familiarity with local bat species (e.g., specific roosting preferences, behavior and seasonal activity, including maternity season date range for the species identified)?
  • Provide at least three recent client references (with phone numbers) for similar projects?
  • Offer a workmanship and materials guarantee for at least two years?
  • Offer a written contract?
  • Use BCI-approved materials and methods

Be wary:

  • If they use scare tactics to convince you that your family is in danger from roosting bats and must act immediately?
  • If they advise or use ineffective methods such as ultrasonic repellents (one study found that ultrasonic devices may even attract bats), or materials that degrade quickly like expandable foam, paper, steel wool or rags to close holes?
  • If they advise or use illegal methods (in the U.S. and most European countries) such as chemical pesticides?
  • If they agree to exclude bats during maternity season.

Common Roosting Species

U.S. and Canadian Bat Species Which Use Human-Made Structures

For more detailed information about these species, including range maps, see

Pallid bat
Antrozous pallidus
Western and southwestern United States and extreme south-central British Columbia, mostly in arid areas. Roosts in various human structures such as bridges, barns, porches, bat boxes, and human-occupied as well as vacant buildings. Winter habitat unknown, presumed to hibernate locally in deep rock crevices.
Jamaican fruit-eating bat
Antrozous pallidus
North America’s only fruit-eating bat, this species occurs in the lower Florida Keys, and occasionally uses buildings throughout its range.
Mexican long-tongued bat
Choeronycteris mexicana
Occasionally roosts in human structures, but is easily disturbed and will readily flee.
Rafinesque’s big-eared bat
Corynorhinus rafinesquii
These bats are known to form nursery colonies in large hollow trees, but as trees in the swamps of the southeastern U.S. have been harvested, they have moved their maternity roosts into old buildings or attics.
Townsend’s big-eared bat
Corynorhinus townsendii
Females form maternity colonies in mines, caves or buildings..
Big brown bat
Eptesicus fuscus
One of the most widespread bats in North America, found across most of the United States and Canada, except for extreme southern Florida and south and central Texas. Maternity roosts are commonly found across North America in buildings, barns, bridges and bat houses. These bats are cold-hardy and occasionally are found hibernating in caves, abandoned mines and buildings in winter. Frequent bat house users, they have overwintered in bat houses from Texas to New York.
Florida bonneted bat
Eumops floridanus
Florida’s largest and rarest bat may be one of the most critically endangered mammals in North America, listed as Critically Endangered by the IUCN. Today this bat is only known to occupy a few bat houses, an abandoned house, and a few tree cavities in south Florida. At least one maternity colony was confirmed using a bat house with a 11⁄2-inch chamber.
Please see our Florida bonneted bats in buildings guide, in English or Spanish to learn how you can protect the Florida bonneted bat in your home or bat box.
Guide [English]
Guide [Spanish]
Greater bonneted bat
Eumops perotis
This is the largest bat in North America, north of Mexico, with a wingspan approaching two feet. It is known to roost in human structures in parts of its range.
Silver-haired bat
Lasionycteris noctivagans
A solitary tree-roosting bat that usually day-roosts behind loose bark but has been found roosting in open sheds, garages and outbuildings, in woodpiles and on fence posts. Sometimes hibernates in buildings.
Lesser long-nosed bat
Leptonycteris yerbabuenae
These bats feed exclusively on the fruit and nectar of night-blooming cacti including saguaro and organ pipe, as well as many species of agave. They are both pollinators and seed-dispersers, and are known to night-roost after feeding in open buildings like barns and carports.
California leaf-nosed bat
Macrotus californicus
These bats may night-roost in open buildings, cellars, porches, bridges, rock shelters, or shallow mines and caves.
Peters’s ghost-faced bat
Mormoops megalophylla
These bats most often roost in caves, rock crevices and abandoned mines, but also occasionally move into old buildings.
Pallas’s mastiff bat
Molossus molossus
In the United States, this species is found only the Florida Keys where they roost in the roof spaces of flat-roofed buildings. Individuals have been found roosting in palm fronds. Throughout the Caribbean, northern Mexico, Central America and northern South America, its roosts include hollow trees, palm fronds, rock crevices, caves, bridges, culverts and buildings. Uses bat houses year-round in Cayman Islands and Puerto Rico.
Southwestern myotis
Myotis auriculus
Southwestern myotis have been found night-roosting in buildings, mines and caves.
Southeastern myotis
Myotis austroriparius
Mostly restricted to Gulf Coast states. Rears young in caves, tree hollows, buildings, bridges, culverts and bat houses. Often non-migratory, hibernates in caves in its northern range and sometimes in tree hollows or buildings farther south. Confirmed bat house user in Florida and Georgia; believed to use bat houses in other Gulf states.
California myotis
Myotis californicus
California myotis are known to form small maternity colonies in cliff crevices, buildings and bridges.
Western small-footed myotis
Myotis ciliolabrum
These bats have been found, in Arizona, roosting under loose bark on trees and in buildings. In Montana, small maternity colonies were found in buildings, caves and mines. One of only two western forest bats that have been found regularly roosting at ground level.
Long-eared myotis
Myotis evotis
Primarily in forests of southwestern Canada and the western United States. Often lives alone or in small groups; females form small maternity colonies in summer. Roosts in hollow trees, under bark, in cliff crevices, timbers of unused railroad trestles, caves, mines and abandoned buildings. Confirmed bat house user in Washington. Day roosts have been found in New Mexico in buildings and mine tunnels. Winter habitat unknown. This western forest bat that roosts regularly at ground level.
Gray myotis
Myotis grisescens
One of the first bat species listed as Endangered by the U.S. Fish and Wildlife Service, 95% of the known population roosts in just nine U.S. caves. Over the years, a few colonies, two of them maternity colonies, have been found roosting in storm sewers, and there have been a few reports of Gray myotis roosting in mines and buildings.
Eastern small-footed myotis
Myotis leibii
This is the smallest myotis species in the eastern U.S. Nursery colonies of 12-20 bats are sometimes found in buildings.
Little brown myotis
Myotis lucifugus
Wooded areas throughout most of Canada and the northern half of the United States, except desert and arid areas. A few isolated populations farther south. Rears young in tree hollows, buildings, rock crevices and bat houses. This is one of the species most commonly found in bat houses. Travels to nearest suitable cave or abandoned mine for hibernation. This species is especially associated with humans, often forming nursery colonies containing hundreds, sometimes thousands of individuals in buildings, attics and other man-made structures. Little brown myotis has been heavily impacted by White-nose Syndrome, resulting in this once-abundant species becoming uncommon throughout much of its eastern range.
Dark-nosed small-footed myotis
Myotis melanorhinus
Widespread across western North America, from central Mexico to British Columbia, Canada. Most scientists consider this bat to be a sub-species of M. ciliolabrum (Western small-footed myotis), but IUCN designated species status in 2008. They hibernate in caves and abandoned mines.
Arizona myotis
Myotis occultus
Some subpopulations of this species have apparently declined or been eliminated. One or two of the three or four known maternity colonies in Arizona have been eliminated, and another has been partially excluded from available buildings. Maternity colonies have been found in the attics of abandoned houses and in crevices between timbers of a highway bridge. A few individuals have been found hibernating in mines in California and Sonora.
Northern long-eared myotis
Myotis septentrionalis
Found in the Upper Midwest, eastern, and some southern states and into Canada. Summer roosts vary. This species, in some parts of their North American and Canadian range, form maternity roosts in buildings and bat houses. Hibernation sites are caves and underground mines. They have also been found roosting beneath tree bark, in rock crevices, as well as caves and mines.
This species is heavily impacted by White-nose Syndrome and in 2015 the species was listed as Threatened by the U.S. Fish and Wildlife Service.
Indiana myotis
Myotis sodalis
One of the earliest bat species designated Endangered by the U.S. Fish and Wildlife Service, hibernating populations of Indiana myotis occur in just three states: Kentucky, Missouri and Indiana, where they form large, highly vulnerable aggregations. In summer, these bats mostly rear their young under loose bark or in tree hollows, but rare maternity colonies have been found in utility pole crevices and bat boxes. Occasionally they use buildings, bridges and bat houses; reported in bat houses in Illinois, Indiana and Pennsylvania. This species is associated mainly with forests and limestone caves.
Fringed myotis
Myotis thysanodes
Night and day roosts of the fringed myotis include caves, mines and abandoned buildings. Little is known about their whereabouts during winter, but they sometimes hibernate in caves and buildings.
Cave myotis
Myotis velifer
Found in southern California and Arizona into central Texas, Oklahoma and south-central Kansas. This species forms nursery colonies, usually numbering in the thousands, in caves, mines, barns, buildings and sometimes under bridges, making them very susceptible to human disturbance. The eastern subspecies hibernates in caves, but the winter habitat of the western subspecies is unknown. Shares bat houses with Mexican free-tailed bats in Texas.
Long-legged myotis
Myotis Volans
This species roosts in trees and rock crevices, and in buildings, and hibernate in caves and mines.
Yuma myotis
Myotis yumanensis
Found in southern British Columbia, Washington, Idaho, Oregon, California, Arizona, extreme western Nevada, eastern Utah, southern Wyoming to western New Mexico. Though occasionally roosting in mines or caves, Yuma myotis are most often found raising their young in buildings or bridges. Winter habitat unknown. Usually found in areas near water. Lives in bat houses from Arizona to British Columbia. Bachelors sometimes roost in abandoned cliff swallow nests.
Evening bat
Nycticeius humeralis
Evening bats get their common name from being one of the first bat species to emerge and forage in the early evening. They are true forest bats, almost never found in caves. Nursery colonies form in hollow trees, behind loose bark, and in buildings and attics. Nursery colonies often share roosts with Mexican free-tailed bats. Winter habitat largely unknown, but often found in buildings and bat houses.Found east of the Appalachians, ranges from southern Pennsylvania to Florida; west of the mountains, from southern Michigan and Wisconsin into Nebraska and south into Texas.
Pocketed free-tailed bat
Nyctinomops femorosaccus
These bats mainly live in desert areas and roost in crevices high on cliff faces, but sometimes also use buildings.
Big free-tailed bat
Nyctinomops macrotis
Desert and arid grassland bats, they typically inhabit rocky out-crops, canyons and cliffs, but occasionally will roost in buildings.
Canyon bat
Parastrellus hesperus
Formerly known as the western pipistrelle, the canyon bat day-roosts in rock crevices, beneath rocks, in burrows, mines and buildings. They hibernate in mines, caves and rock crevices.
Tri-colored bat
Perimyotis subflavus
Found in eastern North America into Canada, except northern Maine, and south to Texas and central
Florida. In summer, the tri-colored bat roosts in rock crevices, caves, buildings and tree foliage. Several tri-colored bats have been reported in bat houses. In the fall, they are sometimes found roosting on apartment building walls, especially on upper levels that are open on both ends. Hibernation occurs deep within caves and mines. Because they prefer humid hibernation sites, tri-colored bats are impacted by White-nose Syndrome.
Mexican free-tailed bat
Tadarida brasiliensis
Common in southern and southwestern United States and north to Nebraska, Colorado, Utah, Nevada and Oregon. The largest maternity colonies are found in limestone caves, but they also roost in large numbers in abandoned mines, under bridges and in buildings. Smaller colonies have been found in hollow trees and frequently in bat houses. Many populations migrate south to overwinter in Mexico and Central America, although colonies in the southeastern U.S. and West Coast typically do not migrate. The densest concentrations of this migrating species are found in Texas, where maternity colonies number in the millions of individuals. Active year round.


It is usually not necessary to enter an attic, basement or other areas to look for bats in structural voids (the spaces between exterior and interior envelopes of a building). Evidence that bats are occupying voids includes seeing them entering or exiting a roost, staining and guano accumulations near active roost entries, audible roost chatter (high-pitched chirping), a distinct musky odor, or repeatedly finding bats on the ground or roosting on an exterior wall.


CREDIT: Austin Bat Refuge


The size and shape of bat guano differs among bat species, but what all insect-eating bat guano have in common is the presence of shiny insect parts in the droppings, and the dry, crumbly texture. Bat guano can sometimes be confused with gecko, lizard, frog or rodent droppings. Rodent droppings are similar in color and size, but are hard and not easily crushed. Gecko droppings are soft and easily crushed, but pellets are tipped with white uric acid deposits not found on bat guanos.


Removing a Single Bat


A single bat flying in the house is rarely cause for alarm and can usually be dealt with easily. In most cases, the “lost” bat is trying frantically to locate an exit and will leave on its own, though leaving may be more challenging for the bat than getting in! The animal can be assisted by opening a window or exterior door. Doors to adjacent rooms should be closed, all lights should be turned on, and ceiling fans turnedoff. It is important to remain quiet and patient as the bat finds its way outside. If the bat does not leave on its own, and if no direct contact with people or pets that may have resulted in a bite has occurred, the bat can be safely captured and released outside.

CREDIT: J. Scott Altenbach

Please Note: A bat that has bitten someone MUST be tested for rabies. If there is a chance that a person or pet was bitten, contain the bat and call your local Animal Control Agency. Then consult with your doctor or your state or local health department. A bite from any wild or unfamiliar mammal, including dogs and cats, should always be taken seriously. If the rabies status of the offending animal cannot be confirmed as negative, post-exposure rabies vaccinations will be required.

Follow these steps to capture a bat for release or for testing:

1. There is no need to chase a bat; simply wait quietly until the bat lands, then, wearing leather gloves, cover it with a small box or other container.

2. Gently, slip a piece of cardboard or a large envelope between the container and the surface where the bat has landed. Be careful that no part of the bat is caught between the box or can and the cardboard. Then slowly turn the box over, containing the bat inside.

* If the bat must remain in the box for several hours (e.g., it’s daytime and you want to wait until dark to release) place a soft cloth (non-terry) in the box before securing a cover. Most bats are very small, and can escape from a container with a loose-fitting lid, so be sure your cover is secure, but not air-tight. Smallholes can be made for ventilation.

3. Place the container in a quiet, safe place and wait until dark before releasing the bat outdoors (a bat released during the day is vulnerable to predators).

4. Most bats need to drop into flight from an elevated location, so don’t place the container on the ground. Place it on its side so the bat can easily climb out onto a tree limb or a second story deck, etc.

5. Watch until the bat flies away.

6. If the bat appears unable to fly, contact a local bat rehabilitator. You can search for one by state at: HERE OR your state wildlife agency or Department of Natural Resources.


Bats found in interior (living or working) spaces are usually there by accident and a single bat flying inside does not necessarily indicate that a colony is in residence. Occasionally a bat may fly through an open door or window, or be carried in by a pet. These accidental visitations can be prevented by keeping doors and windows screened, chimneys capped, and exterior basement or attic doors closed and in good repair.

Bats that roost in buildings are usually in structural voids, the spaces between the exterior and interior envelopes of a building.

Bats enter voids through openings on the exterior of buildings. A colony may remain unnoticed unless someone sees, hears or smells them. When a resident colony is present in the structure, lost bats may find their way into the living area once or twice a year. These events are usually rare, but may occur during the summer maternity season (lost juveniles), or when they awaken briefly from winter hibernation.

Myotis Yumanensis
CREDIT: Bruce D. Taubert
Pallid bats roost inside bridge crevice
CREDIT: Bruce D. Taubert


Potential access areas for bats include structural penetrations as small as 5/16” (8mm) x 1½” (38 mm), or holes 5/8” (16mm) x 7/8” (22 mm), which can include expansion joints, holes, cracks or crevices on the exterior of a structure. As a general rule, if you can get your pinky finger in, a bat can enter. Most bat species choose roost entries in high, out-of-the-way areas (above 10 feet), but in some cases, bats will enter basements, cellars and other areas beneath a house.

Small bat colonies can usually be tolerated and simply left alone, but bats should always be prevented from entering human living quarters.

The first step in exclusions is to inspect the building’s interior for small openings through which bats could enter. All openings connecting the attic or other potential roosting areas to living quarters should be sealed, while entry points on the outside of the building are left open. Caulking, flashing, screening or insulation can be used to seal most openings on the inside. Draft guards should be placed beneath doors to attics; electrical and plumbing holes should be filled with steel wool, caulking or weather stripping.

Caulking, flashing, screening or heavy-duty mesh can be used to bat-proof most openings on the outside. Expanding foam or similar products should never be used to seal cracks in a building where bats are active because they can become caught in it. Caulking should be water-based and applied early enough in the day so it has time to dry before bats emerge in the evening.


Catching bat with box


Interior access can be prevented without disturbing the colony by closing interior openings such as those around plumbing or gas pipes, electrical wiring, or heating and air conditioning units found in utility closets, cabinets, behind appliances, and under sinks. Ensuring an interior “bat-free zone” will prevent the stress (for bat and human) of the sudden appearance of a flying bat in the home or workplace, and allows any further exclusion actions to be carefully considered and planned.

Although interior openings can be closed to prevent bat access to the living space, closing exterior penetrations can be fatal to roosting bats and should never be done without a solid plan to prevent entrapment.

Because entrapment occurs inside walls and other areas that are away from human view, exclusion attempts (or any event that prevents bats from leaving a building) can cause significant mortality that is rarely documentedand often unnoticed, making it nearly impossible to accurately quantify. Evidence of entrapment may include numerous bats suddenly appearing in the living space of a building. If recognized and acted upon quickly, bat mortality may be avoided. Signs that trapped bats have died of dehydration and starvation include strong putrid odors, and dark stains on interior walls or ceilings caused by seepage from decomposing bats.

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