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Frequently Asked
Questions and
FREE Bat House plans
Bat House Basics
Bat House Design.
You should consider design when selecting your
bat house. According to research, larger bat
houses (multi-chamber) have higher occupancy
rates than the smaller houses. Look for
"Certified" bat houses to ensure your bat house
is constructed to the appropriate dimensions.
All landing areas and partition surfaces should
be rough. Ventilation gaps are crucial to
maintaining variable temperatures and
ventilation. Habitat.
Placing you bat house near water source
such as a stream, river, lake, pool or even
birdbath will exponentially increase your
chances of attracting and keeping bats.
Placement.
You may place your bat house on a pole, building
or a dead or un-branched portion of a tree;
however, bat houses mounted on poles or
buildings tend to have a higher occupancy than
those mounted on trees. For mounting on
buildings, wood or stone buildings are best, and
your bat house should be mounted under the eaves
with sun exposure. You should mount your house
15-20 feet above the ground. Avoid areas that
are brightly lit at night.
Sun Exposure.
You should place your bat house where it will
receive at least six hours of sun if you live in
a region where average July temperatures range
from 80-100 degrees Fahrenheit. If you live in a
region where average July temperature are less
than 80 degrees Fahrenheit, you should mount
your bat house where it will receive at least 10
hours of sun. See our region map for
staining/painting recommendations.
You may mount your box at any time of the year,
but those boxes mounted in the spring are often
occupied more quickly. If you are evicting a
colony of bats from a building, a box should be
mounted several weeks prior to the eviction.
The Benefits of Bats
Many people have serious misconceptions about bats.
Myths that they are vicious carriers of rabies and
pests are abundant. The fact is that bats are actually
quite harmless and are important indicators of a
healthy environment. Because bats are sensitive to
high pollution and pesticide levels, they are useful
as a warning sign to potential environmental problems.
Bats can also be important weapons in combating
insects that are actually dangerous to humans.
With the increased media coverage of deaths caused by
the West Nile Virus, many people are looking for
effective ways to prevent the spread of the disease.
As most of us are aware, the West Nile Virus is
primarily spread through mosquitoes. Mosquitoes make
up a significant portion of a bat’s diet. A small bat
can capture more than 1,200 mosquitoes in a single
hour! Bats cannot contract the West Nile Virus by
eating infected mosquitoes. Besides mosquitoes, bats
can help control the populations of beetles, moths,
and leafhoppers. Many insects can hear bats up to 100
feet away and will avoid those areas occupied by bats.
The effectiveness of bats in some areas diminishes the
need for pesticides that can harm both the pests and
their natural predators.
One of the most effective and environmentally friendly
ways to reduce the mosquito population near your home
is to install a bat house. Bat house sizes range from
holding a dozen or so bats to having enough space for
a colony of 500 bats. Most North American bats prefer
to live in large groups, called colonies, so a
mid-sized house (100-300 bats) is typically
recommended. A bat house may be mounted on a tree,
pole, or building; however, houses mounted on poles or
buildings tend to have a slightly higher occupancy
than those mounted on trees. For mounting on
buildings, wood or stone buildings are best, and your
bat house should be mounted under the eaves with some
sun exposure. You should mount your house 15-20 feet
above the ground where it will not be exposed to
bright lights. Temperature is also a consideration.
You should place your bat house where it will receive
at least six hours of sun if you live in a region
where average July temperatures range from 80-100
degrees Fahrenheit. If you live in a region where
average July temperature are less than 80 degrees
Fahrenheit, you should mount your bat house where it
will receive at least 10 hours of sun.
If you are interested in learning more about bats, you
may wish to consider purchasing one of the following
books:
Bat FAQ
Why would I want to attract bats?
Bats are important indicators of a healthy
environment. Because they are sensitive to high
pollution and pesticide levels, they are useful as a
warning sign to potential environmental problems.
Also, bats can be important weapons in combating
insects that are actually dangerous to humans. A
small bat can capture more than 1,200 mosquitoes in
a single hour! Also, bats cannot contract the West
Nile Virus by eating infected mosquitoes. Besides
mosquitoes, bats can help control the populations of
beetles, moths, and leafhoppers. Many insects can
hear bats up to 100 feet away and will avoid those
areas occupied by bats. The effectiveness of bats in
some areas diminishes the need for pesticides that
can harm both the pests and their natural predators.
Do I have bats in my area?
Bats are found on every continent except for
Antarctica. They are particularly abundant in North
America, and many people in the United States and
Canada have bats in their backyard without even
knowing it.
What types of bats are in my area?
Most areas have several different species of bats.
The Big Brown Bat and the Little Brown Bat are the
most abundant bats in the United States, and are the
most frequent users of bat houses. Other species
that may be in your area include the Pallid Bat and
the Brazilian (Mexican) Free-Tailed Bat. You can
often find out what other types of bats reside in
your area by calling your local park service.
Putting up a bat house is the first step toward
attracting bats. Suitable housing for bats is
rapidly decreasing in many areas, as many people
view them as pests and try to evict them from their
homes. Many people inquire about purchasing bats for
their bat house. Bats are a protected species and
are considered public domain, which means that it is
illegal to own, sell, or purchase bats.
Should I use bat guano on or near my bat house?
Many people think that by spreading bat guano on or
near their bat house, it will attract a bat colony.
This has not been scientifically proven, and this is
generally discouraged because of the risk of
exposure to harmful bacteria than can exist in the
guano.
What size bat house do I need?
You should always consider design when selecting
your bat house. According to research, larger bat
houses (often called nursery houses) have higher
occupancy rates than the smaller houses. We often
recommend a minimum capacity of 100-300 bats.
Multiple bat houses will often increase occupancy
rates. By combining a larger house for the females
and their pups and a smaller house for the more
solitary males, people are able to establish larger
and more stable bat colonies. In addition to size,
there are other factors to consider. All landing
areas and partition surfaces should be rough to
allow bats to easily cling when landing and
roosting. Ventilation gaps are important where
average July temperatures exceed 85 degrees
Fahrenheit.
Where should I place my bat house?
You may place your bat house on a tree, pole, or a
building; however, boxes mounted on poles or
buildings tend to have a higher occupancy than those
mounted on trees. For mounting on buildings, wood or
stone buildings are best, and your bat house should
be mounted under the eaves with 6-10 hours of sun
exposure depending on your region. You should mount
your house 15-20 feet above the ground where it will
not be exposed to bright lights. Also, you should
place your bat house where it will receive at least
six hours of sun if you live in a region where
average July temperatures range from 80 to100
degrees Fahrenheit. If you live in a region where
average July temperature are less than 80 degrees
Fahrenheit, you should mount your bat house where it
will receive at least 10 hours of sun.
Should I paint my bat house?
While it is not necessary to paint a bat house,
doing so can often help in regulating the
temperature inside the house. Bat houses in warmer
areas, such as the southern United States, may
benefit from light colored paint. Cooler areas, such
as the northern U. S. and Canada, may benefit from a
darker color to help absorb more warmth from the
sun. Do not paint inside the house, as the bats need
a rough natural surface to hang from when they are
roosting during the day.
When should I put up my bat house?
You may mount your box at any time of the year, but
those boxes mounted in the spring are often occupied
more quickly. If you are evicting a colony of bats
from a building, a box should be mounted several
weeks prior to the eviction.
How do I know if I have bats in my bat house?
One easy way to find out whether or not your bat
house is occupied is to look for bat guano (bat
droppings) under or near the bat house. Another way
is to shine a strong flashlight up into the house.
It is recommended that you only do this once a week,
as frequently disturbing a colony can cause them to
abandon the bat house.
Should I clean my bat house?
Bat houses are relatively maintenance free, so you
should not have to clean your bat house. General
maintenance, such as repainting the house, should be
done when the bats have left to hibernate for the
winter.
I put up a bat house, but still do not have any bats. What can I do?
Attracting a colony can take some time, and many
different factors are involved in the process. The
first consideration is the location of the house. Is
it up high enough? Is it close enough to water? Are
there adequate food sources nearby? The second
consideration is temperature inside the house. If
the average temperature is too hot or too cold or is
inconsistent, bat colonies may not stay. By limiting
or increasing the amount of sunlight a house
receives in order to maintain a consistent warm
temperature. Other factors that affect bat house
occupation include the use of pesticides nearby,
human activity, and lack of vegetation.
How do I get bats out of my home?
Merely putting up a bat house will not lure a bat
colony out of a house. Successfully evicting a bat
colony requires a few steps. The first step is to
inspect the inside of the house for small openings
through which bats could enter. All openings
connecting the attic or other roosting areas to
inside living areas should be sealed, although entry
places on the outside of the house should be left
open, allowing bats to exit. At dusk, watch the bats
leaving the house to locate exactly where openings
are located. Be sure to scout all sides of the house
as there is often more than one opening. Entry
places should be covered with a plastic mesh or
netting that will allow the bats to exit by crawling
under the mesh, but not re-enter the house. You
should not evict bats during the months of June,
July, or August, because there could be many younger
bats that have not developed their flight abilities
and are dependent on their mothers for food. Also,
remember that you will want to put up a bat house
nearby several weeks before the planned eviction. It
is best to put the bat house in a place close by
where the bats will become accustomed to it.
Approximately 70 percent of all bats are
insectivores, including the majority of North
American bats. North American bats primarily feed on
night flying insects, especially mosquitoes, and are
known to eat beetles, moths, and leafhoppers.
Will bats harm people, pets, or birds?
It is important for people to remember that bats are
wild animals and should be allowed to live in their
natural environments. Bats are not aggressive
animals and do not intentionally attack people or
other animals, however, they will bite if touched.
Birding enthusiasts should not worry about
competition between bats and birds. Since bats are
nocturnal, they rarely come in contact with most
birds. Also, there is rarely competition for food
since there is not typically a shortage of insects
that are consumed by both bats and insect eating
birds, such as the purple martin.
Many people have serious misconceptions about bats.
Perhaps one of the most popular of which is the
belief that bats are vicious carriers of rabies. The
fact is that bats are actually quite harmless, and
do not exhibit any higher percentage of rabies
infection than any other animal species. In fact,
bats infected with rabies usually do not exhibit the
aggressive behavior that often occurs with rabies
infection in other animals. Rabies infection
normally paralyzes the bat, so do not pick up a bat
that may be lying on the ground without protective
covering. If possible, it is recommended to have a
pest removal specialist remove the potentially
infected bat.
In most of North America, bats hibernate from late
Fall until early Spring. They often seek out caves
and abandoned mines, and will migrate from their
current homes (buildings, bat houses, etc.) to
warmer, more secure places. Bats in warmer climates,
such as the southern United States, do not
hibernate. Instead, they go into a state of torpor
if outside temperatures approach 32 degrees
Fahrenheit. Torpor is a state of inactivity in which
the bats stay in their day roosts for extended
periods of time to conserve energy until
temperatures begin to rise.
Where can I find bat house plans?
Bat
Builder's Handboook by Merlin D. Tuttle and
Donna L. Hensley that includes bat house plans as
well as general information about bats. In addition,
you may find plans online at:
People all over the world have discovered the benefits
and wonder of using bat houses to attract bats to their
own backyards. We hope you will join them by providing
new homes for these gentle and fascinating mammals with
a voracious appetite for troublesome insects.
Lone Star Woodcraft bat houses are hand made in the
U.S. using BCI’s more than 10 years of analyzed
data from thousands of volunteer Research Associates to
determine the most effective ways to attract bats to
your bat house.
The following pdf documents will answer many of your
basic questions:
Criteria
for Successful Bat Houses (pdf)
Free
single chamber bat house plan! (pdf)
Attracting
Bats (pdf)
Below is just a short list on some of the fun ways
individuals and special groups are reaching out
globally. Although we may not be able to list everyone
everywhere, we do appreciate your support. Please let us
know how we can help extend your batty efforts.
-
BatFest. Over our recent Labor Day Weekend
Roadstar Productions, known for organizing major
festivals in Austin such as the Annual ROT Biker Rally
and The Pecan Street Festival, began yet another
annual tradition which will serve as the
Congress Ave. Bridge’s season finale for our
beloved Austin bats.
- Le Cuvier Winery –
Mighty
Murcielago Red Bat Cuvée.
-
The Dark Place held a special benefit to support
bats, summer 2005.
- REI Bat Float – a monthly kayaking adventure on
Town Lake, Austin, Texas, to visit the bats in season.
Attendees all receive memberships to BCI.
How dangerous are bats?
Bat rabies accounts for approximately one human death
per year in the United States. Thus, some people
consider bats to be dangerous. Nevertheless, dogs which
often are considered "man's best friend," attack and
kill more humans annually than die from bat rabies in a
decade. Statistically speaking, pets, playground
equipment, and sports are far more dangerous than bats.
Clearly, bats do not rank very high among mortality
threats to humans. Nevertheless, prudence and simple
precautions can save lives.
What is rabies, and how is it transmitted?
Rabies is an infectious viral disease that invades
the central nervous system of humans and other
warm-blooded animals. A wide variety of mammals can
contract the disease, but it is most often noticed in
dogs, cats, foxes, raccoons, skunks, coyotes, bats, and
livestock. Worldwide, more than 30,000 humans die of
rabies each year, 99% of these cases resulting from
contact with dogs. In the United States, due to highly
successful dog vaccination programs, transmission from
dogs is now rare, eliminating the vast majority of human
cases. Rabies is nearly always transmitted by a bite,
though non-bite exposures can result from contact
between infected saliva or nervous tissues and open
wounds or the mucous membranes of the eyes, nose, or
mouth. Careless handling is the primary source of rabies
exposure from bats. Rabies virus has not been isolated
from bat blood, urine or feces, and there is no evidence
of air-borne transmission in buildings. Two cases of
aerosol transmission were reported in the 1950s in Texas
caves that support very unusual environments. However,
no similar cases have occurred since, despite the fact
that many thousands of people explore bat caves each
year. No such transmission has occurred outside or in
buildings.
Which bat variances of the rabies virus have been
transmitted to humans?
Rabies virus variances associated with six of the 45
bat species living in the continental United States have
been transmitted to humans. These include the
silver-haired bat (Lasionycteris noctivagans), the
Mexican free-tailed bat (Tadarida brasiliensis), the big
brown bat (Eptesicus fuscus), the eastern pipistrelle (Pipistrellus
subflavus), and two species that were not positively
identified. These are suspected of having been western (Myotis
ciliolabrum) and eastern (M. leibii) small-footed myotis.
Variances of the rabies virus attributed to bats that
commonly live in buildings have been associated with
eight human fatalities in U.S. history.
Do large bat populations lead to increased incidence
of rabies transmission to humans?
The largest urban bat populations consist almost
exclusively of colonial species, and there is no
evidence linking them to increased transmission to
humans. Tens of thousands of people have closely
observed the emergences of 1.5 million Mexican
free-tailed bats at the Congress Avenue Bridge in
Austin, Texas each summer for over 16 years without
incident. In fact, though Austin, San Antonio, and
several other Texas Hill Country towns likely support
the highest bat densities in America, they have recorded
no human cases of bat-transmitted rabies.
Are bats likely to cause rabies outbreaks in other
wildlife or in domestic animals?
There is no evidence that rabies from bats has ever
triggered an outbreak in other animals. It occasionally
does spill over into other species, causing individual
animals to die, but even this is apparently rare.
Despite the fact that numerous carnivores gather to feed
on the 20 million Mexican free-tailed bats at Bracken
Cave, Texas, no outbreaks of rabies are known from this
source. No transmission from bats to dogs is known to
have occurred, though rare cases of transmission to cats
have been documented. The presence or absence of bats is
irrelevant to the fact that all dogs and cats should be
vaccinated.
What can be done to prevent rabies transmission to
humans?
By far the most important prevention is dog and cat
vaccination. Also, children should be especially warned
never to handle any unfamiliar animal. Explain that wild
animals that can be touched may be rabid and dangerous.
Ninety to 95% of sick bats are not rabid, but taking a
careless chance on being bitten could prove fatal. Any
animal bite should be reported immediately to a family
physician or public health professional for evaluation
as a possible rabies exposure. The U.S. Centers for
Disease Control and Prevention recommend pre-exposure
vaccinations for people who are at high risk of
exposure, such as rabies researchers, veterinarians,
field biologists, and animal rehabilitators. Vaccines
currently available include Imovax (HDCV--a human
diploid cell vaccine) and Rabavert (PCEC--a purified
chick embryo cell vaccine). Vaccinations are
administered on days 0, 7, and 21 or 28. For those at
continued risk of exposure to rabies, a booster dose of
vaccine or serology may be necessary at intervals of 6
months to 2 years.
What are the symptoms of rabies?
Rabies causes fatal inflammation of the brain or
spinal cord. Symptoms most often develop about 10 days
to seven months after infection, and death follows 2-12
days after symptoms appear. Early symptoms in humans
include pain, burning, and numbness at the site of
infection. Victims complain of headaches, inability to
sleep, irritability, muscle spasms of the throat and
difficulty swallowing. Convulsions may occur, followed
by unconsciousness and death. Rabies is often referred
to as hydrophobia because victims fear swallowing.
Drinking or eating can bring on muscle spasms of the
throat. The fear of swallowing also accounts for saliva
accumulation referred to as "foaming" at the mouth.
Infected animals may be either agitated and aggressive
or paralyzed and passive. Dogs, cats, and other
carnivores often become aggressive and try to attack
humans and other animals, but bats are typically
passive. Bats normally bite only in self-defense if
handled, and aggressive behavior is rare even when
rabid.
How should potential exposures to rabid bats be
evaluated and treated?
Any bat that bites a human should be tested for
rabies as soon as possible, and post-exposure treatment
should begin immediately unless the bat is confirmed
negative. Bat bites are typically felt and detected at
the time. Visual examination for bite marks is
unreliable. If visible at all, bites may appear only as
a single tiny puncture or scratch. Most punctures are a
millimeter or less in diameter, and most bat inflicted
scratch marks are less than a centimeter long.
Extenuating circumstances can make detection difficult.
If a lost or sick bat hides in bedding, it could be
inadvertently pinched during one's sleep, bite, and
leave without detection. Also, people hauling in
firewood or moving outdoor lumber piles may accidentally
poke and be bitten by a bat without noticing. These are
obviously remote possibilities, though wearing gloves
when moving wood piles could provide protection. If a
young child or a mentally incapacitated person is found
alone with a bat in the same room and the possibility of
a bite cannot be eliminated, post-exposure treatment
should be considered unless prompt testing of the bat
can rule out infection. When questioning about possible
exposure, it is essential first to calm fears of painful
shots. For the majority of patients, the post-exposure
shots are less painful than tetanus vaccinations. Also,
persons who wake up with a bat in the same room where
they have been sleeping are advised to submit it for
testing, especially if the bat is unable to fly or seems
weak.
What is the recommended treatment for a known or
suspected rabies exposure?
Modern rabies treatment is highly effective and
relatively painless. Post-exposure rabies prophylaxis
should begin as soon after exposure as possible.
According the Centers for Disease Control and
Prevention, exposed humans who have not previously been
vaccinated against rabies should receive an initial IM
injection of Human Rabies Immune Globulin (HRIG), twenty
international units per kilogram body weight or nine
international units per pound of body weight in total.
If anatomically feasible, the full dose of HRIG should
be thoroughly infiltrated in the area around and into
the wound(s). Any remaining volume should be
administered intramuscularly at a site distant from
vaccine inoculation. The HRIG is followed by a series of
five 1.0 ml of either Imovax (HDCV--a Human Diploid Cell
Vaccine) or Rabavert (PCEC--a purified chick embryo cell
vaccine). The vaccination series is given on days 0, 3,
7, 14, and 28. Vaccines are administered intramuscularly
in the deltoid region. Persons who have previously
received rabies vaccination should receive two 1.0 ml IM
doses of either of the two vaccines given above, one on
day 0, the second on day 3.
Where can the vaccine be obtained?
Rabies post-exposure vaccinations can be obtained
from hospitals, emergency clinics, and doctors. If
unavailable locally, vaccines and human rabies
immunoglobulin (HRIG) can be obtained as follows: 1)
Imovax (HDCV) and Imogan (HRIG) from Aventis Pasteur at
(800) 822-2463; 2) Rabavert (PCEC) from Chiron at (800)
244-7668; 3) Bayrab (HRIG) from Bayer at (800) 288-8370.
Additional information is available from the Division of
Viral and Rickettsial Diseases, U.S. Centers for Disease
Control and Prevention at (404) 639-1075 during working
hours, or at (404) 639-2888 on nights, weekends, or
holidays.
Are there other diseases to be concerned about from
bats?
The only other disease of public health concern in
the United States is Histoplasmosis, which is caused by
a fungus, Histoplasma capsulatum. This fungus lives in
soil enriched by bird or bat droppings. Human infection
is common in and adjacent to the Ohio and Mississippi
River drainages where warm, humid climates favor fungal
development. The fungus is rare in dry western and cool
northern climates. It can be present, but is uncommon in
dry, hot attics of buildings. Infection is caused by
inhalation of air-borne spores in dust enriched by
animal droppings. The vast majority of histoplasmosis
cases in humans are asymptomatic or involve no more than
flu-like symptoms, though a few individuals may become
seriously ill, especially if exposed to large quantities
of spore-laden dust. The disease can be avoided by not
breathing dust suspected of being enriched by animal
feces. Risks from bats are no different from those of
birds.
What about West Nile virus?
Despite what you may have heard, bats do not transmit
the West Nile Virus to people or other animals. The
virus is transmitted to people by infected mosquitoes.
Members of only two bat species have been found to be
infected with the virus and, like most other mammals,
bats are "dead-end hosts" - they do not transmit the
virus back to mosquitoes as birds do. Let nature help
Natural predators that feed on mosquitoes - including
bats, birds, fish, and other insects - can play an
important role in reducing insect-borne diseases.
Although no single approach to mosquito control is
appropriate for all locations, encouraging these natural
defenses should be an important part of long-term
control whenever possible. Quick-fix options, such as
wide-scale chemical applications and expensive
mosquito-killing machines, are not practical. They often
endanger human health and threaten non-target insects
and animals. They also, over time, kill far more
predators of mosquitoes than mosquitoes, actually aiding
mosquito population growth and increasing demands for
stronger and more dangerous pesticides. Consider bat
houses. Under the right circumstances, bat houses
(artificial structures for bats) can aid our efforts to
control mosquitoes. Bats eat huge quantities of insect
pests, and some species are fond of mosquitoes. But,
like bluebirds and purple martins, bat populations are
declining for lack of places to live. You can help bats
and reduce the number of insects in your yard by
installing bat houses.
Are there reasons for conserving bats?
Most bats are valuable allies, well worth protecting.
Worldwide, they are primary predators of vast numbers of
insect pests that cost farmers and foresters billions of
dollars annually and spread human disease. In the United
States, little brown bats often eat mosquitos and can
catch up to 1,200 tiny insects in an hour. An
average-sized colony of big brown bats can eat enough
cucumber beetles to protect farmers from tens of
millions of the beetle's rootworm larva each summer.
Large colonies of Mexican free-tailed bats eat hundreds
of tons of moth pests weekly. Bats play key roles in
keeping a wide variety of insect populations in balance.
Yet, they rank as North America's most rapidly declining
and endangered land mammals. The largest known cause of
decline is exaggerated human fear and persecution.
Is it safe to put up bat houses?
Statistically, it's safer than owning a dog or
planting flowers. Flowers attract bees whose stings
account for far more human fatality than bats. Just
banning bicycles or swimming pools would be hundreds of
times more effective in saving lives, but how safe do we
really want to be?
Which kinds of bats are attracted to bat houses, and
what are the risks and benefits?
In the northern United States and Canada, little
brown and big brown bats are the most frequent bat house
users. No one has been known to have contracted a
disease from little brown bats, while only three have
been known to have contracted rabies from big brown bats
in all of U.S. history. In southern areas, the two most
frequent bat house users are twilight bats (Nycticeius
humeralis) and Mexican free-tailed bats. The twilight
bat has a perfect safety record. Only five humans have
been known to have contracted rabies from free-tailed
bats, making them far safer than having dogs in a
neighborhood. Children should be warned to leave bats
alone, just as they learn to leave bees and unfamiliar
dogs alone. Bats that live in our yards, in addition to
eating pests, serve as natural insect repellents. Many
yard pests, especially moths that attack gardens, lawns,
and shrubs, can hear bats from over 100 feet away and
attempt to avoid them by leaving the area.
Should bats be tolerated or encouraged in our
neighborhoods?
There are clear benefits to sharing our neighborhoods
with bats, but as with any wild animal, they never
should be tolerated inside our living quarters. Most
bats that enter living areas are lost youngsters with no
greater interest than a safe escape. They can be chased
out through an open door or window or caught in a
butterfly net, a leather gloved hand, or a coffee can
slowly placed over them while a piece of cardboard is
slid between the bat and wall. Rabies testing is
expensive and unnecessary unless a possible rabies
exposure has occurred. In the vast majority of cases,
exclusion of bats from human living quarters is simple,
inexpensive, and can be accomplished by the homeowner
with minimal instruction. Exclusion of bats from an
entire building is also feasible in most cases, though
professional advice may be needed. More than 80% of bat
colonies living in buildings go undetected by human
occupants, but large colonies can cause odor or noise
problems that justify exclusion. Many people simply
exclude bats from entering living quarters while
permitting them to remain in outer walls or in unused
attics. When bats must be entirely excluded from a
building, providing an adequate-sized bat house nearby
can resolve a nuisance without sending it to a neighbor.
Without such an alternative, evicted bats will attempt
to move into a neighbor's home, or sicken and die,
increasing the probability of being picked up by
children or pets.
How can human living quarters be protected against bat
entry?
Most bats that wander into human living quarters
enter through a loose-fitting door to the outside or an
attic, an open window, an unscreened chimney, or a gap
in an outside wall. They must have spaces at least
3/4-inch in diameter or 3/8 by 7/8 of an inch to enter.
A room by room search will quickly reveal such possible
entry points. Holes or crevices are easily plugged with
steel wool or silicone calking. Chimneys can be covered
with half-inch hardware cloth screening, and loose
fitting doors may be fitted with draft guards. Unlike
rodents, bats do not chew holes, so are easily excluded.
Even when bat colonies cannot be excluded from walls or
attics, they can be kept out of human living areas.
Are there risks of people overreacting to news of
rabies in bats?
Rabies incidents involving bats are often distorted
during media reporting. When risks are not kept in
perspective, panicked people overreact in ways that
increase rather than decrease the risk of rabies.
Attempts to poison or exclude bats from buildings by
inappropriate methods can dramatically increase human
contact, as sick or homeless bats scatter to exposed
positions throughout an entire neighborhood. Efforts to
kill or evict bats invariably center on colonial
species. Silver-haired bats and eastern pipistrelles,
the two bat variances of the rabies virus most
implicated in transmission to humans, overlap big and
little brown bats in both roosting and feeding behavior.
In urban settings, silver-haired bats are apparently
less able to compete with the more colonial species and
are scarce. When frightened humans declare war on bats,
they may actually help these species by reducing their
primary competitors. The public needs to recognize the
inescapability and desirability of coexisting with bats,
as well as how to minimize contact and associated risks.
Collaboration between bat researchers, conservationists,
public health and animal control officials is essential
to progress.
Additional References
Bats and Rabies: A Public Health Guide, A Special
Publication of the U.S. Department of Health and Human
Services. 1998. Brass, D. 1994. Rabies in Bats: Natural
History and Public Health Implications. Livia Press,
Ridgefield, CT, 352 pp Constantine, D.G. 1988. "Health
Precautions for Bat Researchers". Pp. 491-528,
Ecological and Behavioral Methods for the Study of Bats,
(T.H. Kunz, ed). Washington D.C.:Smithsonian Institution
Press, 533 pp. Tuttle, M.D. 1995. "Saving North
America's Beleaguered Bats". National Geographic,
88(2):37-57. Tuttle, M.D. 1997. America's Neighborhood
Bats. Rev. ed. Austin: Univ. of Texas Press, 98 pp.
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