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Nuisance Wildlife: Bats
 Bat control
should be done by excluding entry into buildings, not by killing
bats.
Some people wrongly believe bats are flying mice. In fact, bats
form a separate and distinguishable group of mammals more closely
related to moles, shrews, and even monkeys than to rodents. Bats
are the only flying mammals, and, except for certain unique features,
their anatomy is similar to that of most other mammals.
Bat's wings are very different from those of birds, and built
upon the same general pattern as the limbs of other mammals. The
wing is composed of an upper arm, forearm, wrist, and hand with
thumb and four fingers. The hand and fingers are greatly elongated
in order to spread and control the wing. The hind limbs of the
bat are attached at the hip in reverse, pointing the knees backward.
This arrangement is thought to facilitate the bat's ability to
alight upside down and hang by its toes.
 Bats occur worldwide.
Of the approximately 850 species of bats only 39 occur in the
United States and of those, 17 occur in North Carolina. (For details
on specific species see "A Checklist of North Carolina's
Mammals", North Carolina Game and Fresh Water Fish Commission
(GFC).)
North Carolina bats are highly beneficial because they consume
tremendous numbers of night-flying insects, including mosquitoes.
Bats locate insects at night using a very sophisticated sonar
system (echolocation), emitting supersonic sounds and listening
for echoes. Bats are most frequently seen on warm nights feeding
over bodies of water, around buildings or forest edges, or around
lights. During the day, bats find shelter in a variety of secluded
places, preferring small, dark, poorly ventilated spaces that
heat up during the day. Tree cavities, snags, and especially unpruned
cabbage palms are important roost sites. Due to increasing urbanization,
the number of these natural roosting sites has been reduced and
window shutters, drain pipes, billboards, roof tiles, and attics
have become popular roosting site substitutes.
Bats in the home
The presence of a bat in the home may
be a sign that the house is not weather-tight. If so, take appropriate
measures to locate openings and seal them. The best way to remove
a single bat from the home is not to panic, but simply open a
window in the room. The bat usually will circle the room, using
its sonar, until it detects the open window and flies out on its
own. If possible, stay in the room with the lights on and make
sure the bat leaves. This should only take a few minutes. Another
method is to use leather gloves and simply pick up the bat. Never
handle a bat with bare hands because it may try to bite to protect
itself.
If the bat "disappears" in the room, it probably has
landed behind a curtain or in some hidden nook. In this case:
open a window, turn off the lights, close the door behind you,
and isolate the bat by blocking the space under the door with
a towel. The bat should find its way out within an hour after
dark as long as the weather is not too cold. One or two bats in
the home may mean only that they came in through an open window.
However, their presence could be a sign that a colony of bats
has established a roost in a crawl space or attic. An obvious
sign that a bat colony has taken up residence is when bats are
observed flying in and out of a hole in the house. If they become
a nuisance, the only long-term solution is to bat proof the building
( Figure 1).
Bat Control Methods
In light of bats' beneficial feeding habits, give careful consideration
before implementing any control measures. Pesticides, pollution,
people, and habitat loss have reduced bat populations significantly.
That is why non-lethal control measures are recommended.
Exclusion Method
The only permanent way to get rid of a bat colony is to exclude
them from the building by plugging their entrance holes (bat proofing).
Locating the entrance way(s) to a bat colony is the most important
step before implementing an eviction plan. Time of year is an
important factor. Spring, fall and winter are the best times to
exclude bats in North Carolina. Bats will hibernate during winter
in cold weather climates. If you live in the northern one-third
of the state, wait till after early January to exclude bats and
seal openings. The worst time? From the first of April to approximately
the third week in July, bats form nursing colonies. Exclusionary
measures taken at this time would create major problems. There
is a high probability that lactating mothers and their young are
present. Young bats, not yet able to fly, remain in the roost.
Sealing entrance ways would trap many of the bats, separating
mothers from their young and leaving the young bats to die. The
odor from dead bats is extremely offensive. It also may attract
other bats in the area, increasing bat activity even more. Any
adults trapped inside would try to locate other exits increasing
the possibility of contact with humans.
To remove a bat colony, locate where the bats are entering or
exiting. Since bats leave their roost shortly after sunset, watch
the outside of the house from 30 minutes before sunset until 30
minutes after. Bats may enter and exit through an un-screened
attic vent, a chimney, and cracks or openings along eaves, window
sills, and siding. Note: Bats do not need an opening they can
fly through. A crack only 3/8" wide will admit bats.
Once all entrances have been located, seal all but the primary
entrance. Next install a one-way door over the entrance as shown
in Figure 1 . Wait three or four nights, and if bats are no longer
seen leaving the building, seal the remaining hole. If all the
holes have been sealed, there will be no further problems.
Cracks, separations, or other openings should be repaired as
soon as they are noticed. Keeping the house weather-tight and
energy efficient is the best way to prevent bat problems from
recurring.
Methods of habitat manipulation
Artificial Light.
Since bats prefer dark spaces, artificial light can be used quite
successfully, but only if the light is kept on continuously and
moved regularly. Otherwise, the bats will soon find dark corners
to avoid the light. This method also may cause bats to move deeper
into the house as they avoid the light, making them more likely
to enter living areas and come into contact with people.
Repellents.
Although a number of methods have been devised to repel bats,
this approach is only a temporary solution. Naphthalene (mothball)
flakes can be applied to the area of infestation. As long as a
strong odor remains, bats may not return. The effects will not
last long and repeated applications are required to deter bat
reentry. Ammonia can be used to clean areas infested by bats.
Pans of the solution then can be placed in a former roost to act
as a repellent. Neither of these methods will be successful as
long as bats can reenter the habitat once the odor has begun to
fade. The strong odor is also offensive to humans and repeated
applications may not be a tolerable long-term solution. Repellents
are not as effective as simply waiting for the bat's normal departure
at dusk and taking appropriate exclusionary measures.
Fumigants.
There are serious disadvantages to the use of fumigants against
bats. The results are not permanent, and the building may be re-colonized
at a later time. Also, poisons used in the extermination of bats
may cause an increase in human or pet contact with bats as sickened
bats fall to the ground and slowly die. Even if fumigation quickly
killed all bats present, it would provide only a very temporary
solution at best. Other bats could safely move in within just
2 days unless entry holes are plugged — a solution that would
negate the need for fumigation. If fumigation killed a significant
number of bats within the walls of a home, a serious odor problem
would result. Simple exclusion after the bats' nightly departure
is a far preferable solution.
A fumigant can be considered for bat control only in a real public
health emergency under the authority of a special permit issued
by the North Carolina Game and Fresh Water Fish Commission and
only after all other feasible methods of exclusion and removal
have failed.
Ultrasonic repellents are ineffective as a deterrent against
an animal that uses ultrasound waves in many aspects of its life.
They may actually attract bats.
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