Bats, People, and Buildings

Issues and Opportunities

Martin J. Pfeiffer

United States Department of Agriculture

Forest

Service

Forest Products

Laboratory

General Technical Report

FPL–GTR–265

February

2019

Copyright MacKenzie Hall, used with permission
Abstract

Bats are amazing animals. They are among the best flyers of

the natural world and are able to maneuver in the dark to

intersect small flying insects. Bats consume large quantities

of insects, and this helps hold down the populations of pests

that could otherwise destroy agricultural crops and forests.

Bats also pollinate many species of plants that provide us

with food and medicine. Most people in the United States

view bats as pests, and this view has undoubtedly

contributed to precipitous declines for some species. 

However, in much of Europe, bats are protected and

measures are taken to incorporate bat housing into buildings

and bat-friendly habitat into neighborhoods. Many bat

species in the United States also take advantage of human

structures. With good design, bat housing could be

incorporated into buildings and other structures and could 

provide support for U.S. bat populations. This publication

provides an overview of resources available to help people

who want to support bats with their existing structures

and/or new building projects.

Keywords: bats, buildings

February 2019 

Pfeiffer, Martin J. 2019. Bats, people, and buildings: issues and 

opportunities. FPL–GTR–265. Madison, WI: U.S. Department of

Agriculture, Forest Service, Forest Products Laboratory. 9 p.

A limited number of free copies of this publication are available to the 

public from the Forest Products Laboratory, One Gifford Pinchot Drive,

Madison, WI 53726-2398. This publication is also available online at

www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries

in the United States and elsewhere.

The Forest Products Laboratory is maintained in cooperation with the

University of Wisconsin.

The use of trade or firm names in this publication is for reader information

and does not imply endorsement by the United States Department of

Agriculture (USDA) of any product or service.

Contents

Introduction........................................................................ 1 

Bats .................................................................................... 1 

Bats and Buildings ............................................................. 2 

Special Considerations....................................................... 6 

Further Research ................................................................ 8 

References.......................................................................... 8 

English unit Conversion factor SI unit

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

T°F T°C = (T°F – 32)/1.8 T°C

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offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national 

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Introduction

Buildings pose unique opportunities and challenges for 

wildlife. The structural components of buildings can mimic 

conditions found in natural landscapes and can provide 

homes for wildlife. In some cases, these “homes” can help 

sustain species of wildlife that are experiencing loss of their 

natural home sites. For example, bats that roost in buildings 

may do so because of the loss of old, decaying trees that 

provided natural roosts under bark or within cavities.

Building sites can also benefit wildlife by providing oases 

for food, water, and/or other necessities of survival. Bird 

feeders supplement natural food sources for not only birds 

but voles, mice, squirrels, rabbits, raccoons, bears, and other 

wildlife. The smaller animals may, in turn, attract hunters

such as hawks, owls, fox, and coyotes. Landscaping may 

add water features, berry- and nut-producing shrubs, and 

cover for animals.

Buildings can also create problems for wildlife. A 

significant source of problems arise from conflicts with 

people. Bats that enter homes and office spaces may cause 

distress for some people and can result in undue harm to the 

animal itself. Woodpeckers that drum on wood siding can 

damage buildings and frustrate owners. Skunks who make 

dens near buildings may not be welcomed by landowners or 

resident pets. These are but a few examples of the conflicts 

that can occur when wildlife intersect with buildings and 

surrounding land.

Buildings can also cause direct issues for wildlife. Estimates 

range as high as one billion birds lost each year to collisions 

with building glass. Feral cats, primarily found near 

buildings, account for an additional billion bird deaths every

year. Artificial lighting associated with buildings can 

discourage bats and disorient migrating birds.

Many species of wildlife found in the United States are 

threatened by loss of habitat and population declines. A 

number of bat and bird species, in particular, are showing 

precipitous declines in their populations. Some of these 

species are capable of or, in some instances, thrive on living 

among human populations.

A number of bat species, in particular, are attracted to 

building structures. This report will address issues and 

opportunities associated with bats and buildings.

Bats

Bats in North America have historically been persecuted by 

humans. There are undoubtedly multiple, interconnecting 

factors that account for negative reactions to bats. However, 

much of what people think and feel about bats is based on 

misinformation. Bats in most mythology and folklore are 

dirty and blind, get tangled in people’s hair, and associate 

with vampires. Bats are often depicted in television and 

movies as ominous creatures and bad omens. These myths 

are incorrect and obscure many marvelous characteristics of 

bats. The Truth about Bats from Bat Conservation 

International (Austin, Texas, USA) gives more information 

on this topic (BCI 2018a).

The Amazing Bat

Bats are amazing animals, and no less so than well-regarded 

animals such as (wise) owls, (majestic) eagles, and 

(cunning) foxes. Bats form the second largest order of 

mammals in the world. There are more than 1,000 species of 

bats in the world, and all can fly (USDI 2017). In fact, they 

are the only species of mammal that fly under their own 

power. Because of their unique wing structure, bats are 

capable of incredible maneuvers to capture insects in flight.

Bats are nocturnal and feed primarily at dusk, dawn, and 

night. Although bats can see as well as humans, they use 

echolocation to maneuver in the dark. This involves 

emitting high frequency sounds and listening for the return 

echo that occurs when sound reflects off an object. Bats can

discern minute differences in these echoes and it is this 

ability that allows them to fine tune flight speed and 

direction and time their arrival to intersect a small flying 

insect. This same ability enables bats to navigate around

buildings, trees, and other obstacles in flight.

Bat echolocation is so advanced that the United States Navy 

has studied bats with the hope of improving sonar 

capabilities (ONR 2002). Bats can separate two sounds 

received just a few microseconds (three-millionths of a 

second) apart. This is faster than historical sonar capabilities 

(at 12 microseconds) and gives bats a unique advantage: 

they can distinguish objects whose size and shape differ 

only by the width of a human hair, even while flying at high 

speed in the dark. Scientists are also studying bat 

echolocation for other purposes. For example, someday,

blind people may be able to take advantage of echolocation 

Bats, People, and Buildings

Issues and Opportunities

Martin J. Pfeiffer, Wildlife Biologist

USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin, USA
General Technical Report FPL–GTR–265

2

technology and “hear” their way through a room

(NOVA Next 2013).

Benefits of Bats

Bats benefit forests and farms by pollinating flowering 

plants and distributing seeds. Bats, together with birds, 

predominate the distribution of seeds and reforestation of 

rainforests worldwide. In one study, bats occupying 

artificial roosts distributed the seeds of 69 different plant 

species to deforested areas in Costa Rica (Kelm and others

2008). Worldwide, more than 300 species of fruit, including 

bananas, dates, Brazil nuts, coconut, vanilla, and avocado, 

depend on bats for pollination (USDA FS 2018). Eighty

different medicines come from plants that are dependent on 

bats for pollination (USDI 2017).

Bats also eat insect pests that can damage forests and 

agricultural crops such as tomatoes, beans, carrots, apples, 

peaches, grapes, oats, rice, wheat, almonds, pecans, and 

peanuts. One California farm has incorporated bat houses to 

host approximately 1,000 bats that consume codling moths, 

a major source of damage to walnut crops (Donahue 2015). 

Research in Indiana concluded that an average colony of 

150 big brown bats consumes sufficient cucumber beetles to 

avert 33 million rootworms, a major corn pest, every year

(Whitaker 1995). An estimated 100 tons of insects are 

consumed each summer night by Mexican free-tailed bats 

living in Bracken Cave near San Antonio, Texas, USA

(TPW 2016).

Bats at Risk

Almost half (22 of 47) of the bat species in the United States 

are at risk because of precipitous declines in population, loss 

of habitat, disease, or other causes (Table 1). Seventeen 

species or subspecies are listed as vulnerable, imperiled, 

critically imperiled, possibly extinct, or presumed extinct on 

NatureServe Explorer, an authoritative source for 

conservation information about more than 50,000 plants, 

animals, and ecological communities of the United States 

and Canada (NatureServe 2018). Eight species or subspecies 

are listed under the Endangered Species Act (ESA) (USDI 

FWS 2018a). Nine species have been confirmed susceptible 

to a significant new disease (white-nose syndrome) that 

threatens their survival (USDI FWS 2018b).

White-nose syndrome is a fungal disease causing 

unprecedented mortality and precipitous declines in 

populations for some species of hibernating bats. An 

estimated 6 million bats have died, mostly in the eastern 

United States, since the disease was first documented in 

2006. The disease was first discovered in the United States 

on the east coast, is currently found in 32 states, and 

continues to move westward. Sixteen species of bats have 

been detected with the fungus (Pseudogymnoascus 

destructans) thought to cause the disease, and nine species 

are susceptible to the disease itself (USDI FWS 2018b).

Protections for Bats

Bats have relatively few protections in the United States. Of 

the 47 species found in the United States, only eight species 

are either completely protected or have subspecies protected 

under the ESA. It is illegal to import, export, take, possess, 

sell, or transport species listed under the ESA. The term 

”take” means to harass, harm, pursue, hunt, shoot, wound, 

kill, trap, capture, or collect or to attempt to engage in any 

such conduct (USDI FWS 2018c). The prohibition against 

“take” includes destruction of critical habitat (Hodges 

2010).

Aside from the ESA, bats are not consistently protected 

across species and state lines. For some species, federal, 

state, and other partners have developed and continue to 

improve management plans for their protection. Some states 

have developed specific legislation to protect bats. For 

example, several states prohibit exclusion of bats from 

buildings that are hosting active maternity colonies during 

critical time periods. Bats are also protected from control by 

pesticides. Environmental Protection Agency (EPA)

regulations only allow the application of pesticides for 

species listed on labels, and bats are not listed on the labels 

of any pesticides (BCI 2018b).

Bats and Buildings

Importance of Buildings

Of the 47 species of bats found in the United States, 35 are 

known to use human structures, including buildings and

bridges (BCI 2018c; Table 1). Fourteen species use bat 

houses (BCI 2013). By virtue of their ability to fly and, for 

many species, crawl through small openings, bats are adept 

at entering buildings. Buildings can provide space for 

feeding, mating, rearing young, hibernation, 

thermoregulation, and protection from predators.

For some bat species, human structures have become a 

lifeline, slowing population declines and perhaps even 

staving off extinction. For these species, something has 

changed, causing their historical, natural roosts to no longer 

be available or sufficient to meet their needs for shelter and 

reproduction.

Use of Buildings

Different bat species take advantage of different structural 

features of buildings. In general, structural features used by 

bats can be simplified to four main categories: (1) cracks, 

crevices, and small cavities; (2) exterior roosts; (3) attics or 

similarly sized protected open spaces; and (4) flyways for 

bats that cannot crawl and must fly to roosts.

1. Cracks, Crevices, and Small Cavities

Cracks, crevices, and small cavities are defined as small 

spaces that provide sufficient space for one or more bats to 
Bats, People, and Buildings: Issues and Opportunities

3

will typically crawl into the space. Besides cracks and 

Table 1—Bat species of the United States

Species States found

Uses

structures?

At risk to

P. destructans?

At risk to 

white-nose 

syndrome?

NatureServe at 

risk?

Listed per 

Endangered 

Species Act

(ESA)?

Pallid bat

Antrozous pallidus

AZ, CA, CO, ID, KS, MT, 

NM, NN, NV, OK, OR, TX, 

UT, WA, WY

Yes Yesa

Jamaican fruit-eating bat

Artibeus jamaicensis

FL Yes

Mexican long-tongued bat

Choeronycteris mexicana

AZ, CA, NM, TX Yes Yes

Rafinesque’s big-eared bat

Corynorhinus rafinesquii

AL, AR, FL, GA, IL, IN, 

KY, LA, MO, MS, NC, OH, 

OK, SC, TN, TX, VA, WV

Yes Yes Yes

Townsend’s big-eared bat

Corynorhinus townsendii

AR, AZ, CA, CO, ID, KS, 

KY, MO, MT, NC, NE, 

NM, NN, NV, OK, OR, SD, 

TN, TX, UT, VA, WA, 

WV, WY

Yes Yes Yesb Yesc

Big brown bat

Eptesicus fuscus

AK, AL, AR, AZ, CA, CO, 

CT, DC, DE, FL, GA, IA, 

ID, IL, IN, KS, KY, LA, 

MA, MD, ME, MI, MN, 

MO, MS, MT, NC, ND, NE, 

NH, NJ, NM, NN, NV, NY, 

OH, OK, OR, PA, RI, SC, 

SD, TN, TX, UT, VA, VT, 

WA, WI, WV, WY

Yes Yes Yes

Eastern small-footed bat

Myotis leibii

AR, CT, GA, KY, MA, 

MD, ME, MO, NC, NH, NJ, 

NY, OH, OK, PA, SC, TN, 

VA, VT, WV

Yes Yes Yes

Gray bat

Myotis grisescens

AL, AR, FL, GA, IL, IN, 

KS, KY, MO, NC, OK, SC, 

TN, VA

Yes Yes Yes Yes

Indiana bat

Myotis sodalis

AL, AR, CT, GA, IA, IL, 

IN, KY, MA, MD, MI, MO, 

MS, NC, NJ, NY, OH, OK, 

PA, SC, TN, VA, VT, WV

Yes Yes Yes Yes Yes

Little brown bat

Myotis lucifugus

AK, AL, AR, CA, CO, CT, 

DC, DE, FL, GA, IA, ID, 

IL, IN, KS, KY, MA, MD, 

ME, MI, MN, MO, MS, 

MT, NC, ND, NE, NH, NJ, 

NM, NV, NY, OH, OK, 

OR, PA, RI, SC, SD, TN, 

UT, VA, VT, WA, WI, WV, 

WY

Yes Yes Yes Yes

Northern long-eared bat

Myotis septentrionalis

AL, AR, CT, DC, DE, FL, 

GA, IA, IL, IN, KS, KY, 

LA, MA, MD, ME, MI, 

MN, MO, MS, NC, ND, 

NE, NH, NJ, NY, OH, OK, 

PA, RI, SC, SD, TN, VA, 

VT, WI, WV, WY

Yes Yes Yes Yes Yes

Yuma bat

Myotis yumanensis

AZ, CA, CO, ID, MT, NM, 

NN, NV, OK, OR, TX, UT, 

WA, WY

Yes Yes Yes Yesd
General Technical Report FPL–GTR–265

4

crevices, typical points of entry into buildings include 

Table 1—Bat species of the United States—continued

Species States found

Uses

structures?

At risk to

P. destructans?

At risk to 

white-nose 

syndrome?

NatureServe at 

risk?

Listed per 

Endangered 

Species Act

(ESA)?

Southeastern bat

Myotis austroriparius

AL, AR, FL, GA, IL, IN, 

KY, LA, MO, MS, NC, OK, 

SC, TN, TX, VA

Yes Yes Yes

Tri-colored bat

Perimyotis subflavus

AL, AR, CT, DC, DE, FL, 

GA, IA, IL, IN, KS, KY, 

LA, MA, MD, ME, MI, 

MN, MO, MS, NC, NE, 

NH, NJ, NM, NY, OH, OK, 

PA, RI, SC, TN, TX, VA, 

VT, WI, WV

Yes Yes Yes Yes

Cave bat

Myotis velifer

AZ, CA, KS, NM, NV, OK, 

TX, UT

Yes Yes

Silver-haired bat

Lasionycteris noctivagans

AK, AL, AR, AZ, CA, CO, 

CT, DC, DE, FL, GA, IA, 

ID, IL, IN, KS, KY, LA, 

MA, MD, ME, MI, MN, 

MO, MT, NC, ND, NE, NH, 

NJ, NM, NN, NV, NY, OH, 

OK, OR, PA, RI, SC, SD, 

TN, TX, UT, VA, VT, WA, 

WI, WV, WY

Yes Yes Yes

Florida bonneted bat

Eumops floridanus

FL Yes Yes Yes

Greater bonneted bat

Eumops perotis

AZ, CA, NV, TX Yes

Lesser long-nosed bat

Leptonycteris yerbabuenae

AZ, CA, NM Yes Yes Yes

California leaf-nosed bat

Macrotus californicus

AZ, CA, NV, UT Yes Yes

Peters’s ghost-faced bat

Mormoops megalophylla

TX Yes

Pallas’s mastiff bat

Molossus molossus

AZ, NM, TX Yes

Southwestern bat

Myotis auriculus

AZ, NM Yes

California bat

Myotis californicus

AK, AZ, CA, CO, ID, MT, 

NM, NN, NV, OR, TX, UT, 

WA

Yes

Western small-footed bat

Myotis ciliolabrum

AZ, CA, CO, ID, KS, MT, 

ND, NE, NM, NN, NV, OK, 

OR, SD, TX, UT, WA, WY

Yes

Long-eared bat

Myotis evotis

AZ, CA, CO, ID, MT, ND, 

NM, NN, NV, OR, SD, UT, 

WA, WY

Yes

Dark-nosed small-footed bat

Myotis melanorhinus

AZ, CA, CO, ID, KS, MT, 

ND, NE, NM, NN, NV, OK, 

OR, SD, TX, UT, WA, WY

Yes

Arizona bat

Myotis occultus

AZ, CA, CO, NM Yes

Fringed bat

Myotis thysanodes

AZ, CA, CO, ID, MT, NE, 

NM, NN, NV, OR, SD, TX, 

UT, WA, WY

Yes Yese

Long-legged bat

Myotis Volans

AK, AZ, CA, CO, ID, MT, 

ND, NE, NM, NN, NV, OR, 

SD, TX, UT, WA, WY

Yes
Bats, People, and Buildings: Issues and Opportunities

5

expansion joints and holes (BCI 2012). Bats can navigate 

Table 1—Bat species of the United States—continued

Species States found

Uses

structures?

At risk to

P. destructans?

At risk to 

white-nose 

syndrome?

NatureServe at 

risk?

Listed per 

Endangered 

Species Act

(ESA)?

Evening bat

Nycticeius humeralis

AL, AR, DC, DE, FL, GA, 

IA, IL, IN, KS, KY, LA, 

MD, MO, MS, NC, NE, NJ, 

OH, OK, PA, SC, SD, TN, 

TX, VA, WI, WV

Yes

Pocketed free-tailed bat

Nyctinomops femorosaccus

AZ, CA, NM, TX Yes

Big free-tailed bat

Nyctinomops macrotis

AZ, CA, CO, KS, NM, NN, 

NV, OK, TX, UT

Yes

Canyon bat

Parastrellus hesperus

AZ, CA, CO, ID, NM, NN, 

NV, OK, OR, TX, UT, WA

Yes

Mexican free-tailed bat

Tadarida brasiliensis

AL, AR, AZ, CA, CO, FL, 

GA, KS, LA, MS, NC, NE, 

NM, NN, NV, OK, OR, SC, 

TX, UT

Yes

Eastern red bat

Lasiurus borealis

AL, AR, CO, CT, DC, DE, 

FL, GA, IA, IL, IN, KS, 

KY, LA, MA, MD, ME, MI, 

MN, MO, MS, MT, NC, 

ND, NE, NH, NJ, NM, NY, 

OH, OK, PA, RI, SC, SD, 

TN, TX, VA, VT, WI, WV

Yes Yes

Mexican long-nosed bat

Leptonycteris nivalis

NM, TX Yes Yes

Underwood’s bonneted bat

Eumops floridanus

FL

Western red bat

Lasiurus blossevillii

AZ, CA, NM, NV, TX, UT

Hoary bat

Lasiurus cinereus

AL, AR, AZ, CA, CO, CT, 

DC, FL, GA, HI, IA, ID, IL, 

IN, KS, KY, LA, MA, MD, 

ME, MI, MN, MO, MS, 

MT, NC, ND, NE, NH, NJ, 

NM, NN, NV, NY, OH, 

OK, OR, PA, RI, SC, SD, 

TN, TX, UT, VA, VT, WA, 

WI, WV, WY

Yes Yesf

Southern yellow bat

Lasiurus ega

TX

Northern yellow bat

Lasiurus intermedius

AL, FL, GA, LA, MS, NC, 

SC, TX

Seminole bat

Lasiurus seminolus

AL, AR, FL, GA, LA, MS, 

NC, OK, SC, TX

Western yellow bat

Lasiurus xanthinus

AZ, CA, NM, NV, TX

Spotted bat

Euderma maculatum

AZ, CA, CO, ID, MT, NM, 

NN, NV, OR, TX, UT, WA, 

WY

Allen’s big-eared bat

Idionycteris phyllotis

AZ, NM, NV, UT

Keen’s bat

Myotis keenii

AK, WA Yes

a

Only subspecies pacificus (OR) is considered at risk. b

Only subspecies ingens (AR, MO, OK), pallescens (AZ, CA, CO, NM, NN, NV, OK, OR, TX, WA), townsendii (CA, ID, NV, OR, WA), and 

virginianus (KY, NC, VA, WV) are considered at risk. c

Only subspecies ingens (AR, OK) and virginianus (KY, NC, VA, WV) are ESA-listed. d

Only subspecies oxalis (CA) is considered at risk. e

Only subspecies pahasapensis (NE, SD, WY) and vespertinus (CA, OR) are considered at risk. f

Only subspecies semotus (HA) is ESA-listed.
General Technical Report FPL–GTR–265

6

occupy. Not all bats will use these spaces, but bats that do 

will typically crawl into the space. Besides cracks and 

crevices, typical points of entry into buildings include 

expansion joints and holes (BCI 2012). Bats can navigate 

holes with diameters as small as 5/8 to 7/8 in. Other 

entryways must be at least 5/16 by 1 1/2 in. Internal cavities 

can be as small as the size of a bat (minimally 0.5 by 2 in.

for the smallest of species) or much larger (BC Ireland 

2014).

2. Exterior Roosts

Some bat species use “night roosts” for shelter while 

digesting their food. These exterior roosts serve as 

temporary rest stops during nightly feeding activities. Night 

roosts are chosen for warmth and are often close to feeding 

sites. Areas under small eaves near doorways or under 

overhangs at the corners of buildings may be used. The bats 

are gone by daylight but may leave telltale signs via urine 

stains and guano. Somewhat related, there are also bat 

species that use exterior surfaces as roosts during the day. 

These are generally small populations that hide behind 

shutters or signs on buildings.

3. Attics and Similar Openings

Attics and similarly sized spaces are larger, open spaces that 

provide sufficient space for bats to fly as necessary within 

the space. Entryways for bats must be at least as large as 

those indicated above for cracks, crevices, and small 

cavities. Internal dimensions for the roosting space should 

be 9 by 16 ft or larger (BCT 2012). Joists or beams may be 

necessary for bats to roost. These spaces should be 

completely open and exclude trusses and other potential 

obstacles to flight.

4. Flyways

Flyways allow bats that cannot crawl to fly directly to a 

roost in an attic or other large open space. The needed 

dimensions of the opening depend on the size and wingspan 

of the bat species.

Opportunities for Bats and Buildings

A number of European countries have passed laws that 

protect all resident bat species. Various organizations in 

these countries have developed brochures and booklets to 

help property owners and architects accommodate bats in 

buildings. These include detailed diagrams of the structural 

components useful to bats and how to “build in” housing for 

bats. See Table 2 for a listing of publications for this 

purpose.

Most designs that incorporate space for bats in buildings 

include specially designed bat boxes inside exterior walls or 

decorative boxes on the outside of these walls (Fig. 1). Bat 

boxes incorporated into exterior walls are designed to fit 

between wall insulation and exterior finishing material. Bat

boxes attached to the outside of exterior walls oftentimes 

incorporate design elements that add to, rather than detract 

from, the overall building aesthetics.

Farms, nature lovers, and other individuals with interest in 

bats will often accommodate bats in larger open spaces, 

such as attics, barns, garages, outbuildings, abandoned 

buildings, and other structures without human occupants.

Specifications for building components to accommodate 

bats can be obtained from the sources and publications 

identified in Table 2. Several important considerations are 

briefly described in the following sections.

Special Considerations

Surface Requirements

Bats require surfaces with texture for grip. This is important 

for both roosting and maneuvering. Additionally, surfaces 

must be nontoxic and noncorrosive (BCT 2018).

Thermal Regulation

Bat boxes need to create favorable thermal conditions before 

they will be used by bats. Proper design and location are 

essential. The internal bat box temperature for maternity 

colonies should be between 80 and 100 °F (BCI 2018d). 

Optimal design and location will depend on local climate. 

Some features to consider are bat box color (dark for 

heating), venting (for cooling), sun exposure, and caulking 

(to trap heat). Experimenting and offering multiple boxes, 

designs, and locations will improve your odds of attracting 

bats. See Bat Conservation International’s excellent 

publication Criteria for Successful Bat Houses for more 

information (BCI 2018d).

Landscaping

Bats rely on the same key elements as other wildlife. They 

require habitat that offers food, water, and protection from 

predators. Some species of bats will generally only roost in 

close proximity to water. Ponds and native vegetation, 

besides adding to the beauty and value of urban property, 

can serve as excellent sources of food, water, and cover for 

bats. See Landscape and Urban Design for Bats and 

Biodiversity for specific ideas (Gunnell and others 2012).

Chemical Applications

It is against the law to use poisons to remove bats (BCI 

2018b). Likewise, wood surface treatments containing toxic 

chemicals should be avoided.

Lighting

Although bats have good eyesight, they are nocturnal 

animals. They are adapted to operating in the dark. This 

means that lighting is usually not beneficial, and may be 

problematic, for bats (Stone and others 2015). Lights should 

be situated to avoid shining on bat roosts, openings, and 
Bats, People, and Buildings: Issues and Opportunities

7

flight lines to and from the roost. See Bats and Lighting in 

the UK for ideas on how to avoid the potential negative 

effects of lighting on bats (BCI/ILE 2009).

Remodeling

If a remodeling project is planned for a building hosting 

bats, the project should be timed to avoid disturbance. In the 

summer, some buildings may host maternity colonies. In 

winter, some species of bats hibernate in buildings. In either 

case, disturbance would be detrimental. Some states have 

passed legislation protecting bats during the maternity 

season.

Protecting Human Space

Bat forays into homes and offices are generally not well

received. It is essential that areas incorporating roosts for 

bats be well sealed from the spaces used by people.

Guano

Bat droppings are called guano. Guano is largely made up of 

the exoskeletons of insect prey. It crumbles easily, and

because of its high nitrogen content, it makes good fertilizer. 

Bat roosts in or attached to buildings should provide a 

vertical drop, which will allow gravity to remove the guano. 

Bats also excrete urine. A small ledge at the base of the 

roost opening can help decrease staining to the building 

siding.

Table 2—Publications providing detailed information for incorporating bats into building design

Publication Citation Website

Bats & Buildings BCI 2012 www.batcon.org

Bats and Buildings BCT 2012 www.bats.org.uk

Bat House Builder’s Handbook BCI 2013 www.batcon.org

Bats in Buildings BC Ireland 2014 www.batconservationireland.org

Building Bat Friendly Landschapsbeheer Flevoland 2011 www.eurobats.org

Designing for Biodiversity: A Technical 

Guide for New & Existing Buildings

Gunnell and others 2013 www.ribabookshops.com

Figure 1. Examples of bat boxes available: (a) Bat Box C from Ibstock Kevington (Leicestershire, UK); (b) integrated Eco 

Bat Box from The Nestbox Company (Hampton-in-Arden, UK), preinstallation; (c) integrated Eco Bat Box from The Nestbox 

Company, postinstallation; (d) bat access panel from Schwegler (Heinkelstraβe, Schorndorf, Germany) (with optional back 

plate); (e) bat tube from Schwegler (preinstallation); (f) bat tube from Schwegler (postinstallation). ((a) copyright Ibstock 

Kevington, (b) and (c) copyright The Nestbox Company, and (d), (e), and (f) copyright Schwegler GmbH. All photos used 

with permission.)
General Technical Report FPL–GTR–265

8

Human Health Risks

Bats are one of many wild animals that can carry rabies. 

Rabies is a deadly disease. If you are bitten or scratched by 

a bat, you should seek medical treatment. If possible, 

capture the bat and have it tested for rabies. See Bat 

Conservation International’s publication Bats and Rabies: A 

Public Health Guide for additional information (BCI 

2018e).

Accumulations of guano in the soil or attic can be colonized 

by the fungus Histoplasma capsulatum. Humans can 

become susceptible to the disease histoplasmosis by 

inhaling spores of the fungus. Most infections result in mild 

symptoms, but outcomes can be severe for high-risk 

individuals. With precautions, small quantities of guano can 

be cleaned up with soap and water. Larger quantities should 

be left to environmental health professionals. See the Illinois 

Department of Human Health publication Health Hazards 

Associated with Bird and Bat Droppings for guidance 

(IDPH 2018).

Excluding Bats

As mentioned above, some states have passed legislation 

protecting bats during their maternity season. If a bat is 

found within a building and must be removed, contact your 

state or county wildlife specialist for a recommended 

approach and/or list of reputable contractors.

Seeking Help

A wildlife biologist or similarly trained professional 

specializing in bats should be consulted before undertaking 

any project to incorporate bat housing within buildings. A 

professional can help identify species found in your area, 

narrow down options and develop specifications for bat 

housing, and provide other ideas (for example, landscaping) 

for ensuring an effective solution.

Further Research

Bats have historically not received as much scientific 

attention as other charismatic species (for example, birds, 

deer, and wolves). It’s only recently, with the discovery of 

white-nose syndrome, that research time and money has 

turned to bats. This means that there is a lack of information 

about bat behavior. However, this presents opportunities for 

further research.

One particular research need involves bats and urban areas. 

What bat species are attracted to urban areas of the United 

States? Which species are the “winners” and “losers” as 

landscapes begin to urbanize? Does urbanization help or 

harm at-risk species? How might the long-term trend toward 

larger urban areas affect bat species?

Another area of opportunity for scientific research involves

bats and urban design. How can urban design help bat and 

other wildlife species survive and thrive in urban areas? 

What are the most significant needs of bat species living in 

U.S. urban areas? What are specific urban design elements 

(for example, landscaping configurations) that can help 

species in urban areas? What are the effects of supplemental 

housing (bat boxes) on bat populations in urban areas?

There is a need for additional information about the specific 

housing needs of bat species living in the United States. For 

species that occupy human structures, what are the design 

specifications for building owners who want to encourage 

bats? How can bat biologists, green builders, and other 

architectural innovators work together to ensure sustainable 

building practices that also help secure the future of bats and 

other at-risk wildlife species?

What are the ecological and economic implications of bats 

in urban areas? Do bats significantly affect other flora and 

fauna in urban areas? Do bats in urban areas contribute 

significant insecticide services locally and to adjacent 

agricultural areas? These are all questions that deserve 

further research.

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Bats%20and%20Buildings%20Brochure.pdf. 

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BCI. 2013. The bat house builder’s handbook. Austin, TX: 

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Bats, People, and Buildings: Issues and Opportunities

9

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