DATE:     9/28/00   
WRITER:   Candace Cummings, (864) 656-7146, 
          Clemson Extension wildlife associate
EDITOR:   Giles Singleton, (864) 656-3876

What to do about
bats in your belfry

     CLEMSON -- Have you encountered a stray bat flying around 
in your house? 
     Bats that fly into human living quarters are usually lost
youngsters whose primary goal is a safe escape. They often will 
leave on their own if a window or door to the outside is opened 
while others leading to the rest of the house are closed.
     Bats are not aggressive, even if chased, but they may bite 
if they are grabbed. As with any wild animal, bats should not 
be handled with bare hands.
     You can hasten its exit by catching the bat in flight with 
a butterfly net - swing from behind - or, when the bat lands, 
cover it with a coffee can and slip a piece of cardboard over 
the opening, and then simply release it outside. You can also 
catch it by hand, using leather work gloves to avoid being 
bitten.
     Any sick bat found in the home should be tested for 
rabies.
     If you have a whole colony of bats, exclusion is the 
only effective method of ridding your home of them. There is 
no magic potion or spray on the market to kill or repel bats, 
and there no pesticide is  labeled for use on bats.
     Large colonies of bats must be excluded only in late summer 
or early fall from living quarters or attics, because these 
colonies are usually made up of mothers and their young. If you 
attempt to exclude them when the young have not learned the 
skill of flying, starved young could create a serious odor 
and insect problem. This method of exclusion is also needlessly 
cruel.
     Begin exclusion in early fall, after bats have left the 
building, by covering chimneys and vents with half-inch hardware 
cloth screens; installing draft guards beneath doors and sealing 
any other possible access routes, especially around screen 
doors, windows and plumbing. Bats can enter holes as small as 
3/4 inch in diameter, or 3/8 inch by 7/8 inch. They do not 
chew insulation or otherwise make new holes.
     Their entries can be plugged with silicone caulking, steel 
wool, or, temporarily, with tape.
     If a large bat colony must be evicted from a wall or 
attic, careful observations should be made at dusk to find 
entry holes. The bats must emerge each summer evening to feed. 
The entry holes are also sometimes recognizable by stains 
around the holes or crevices used or by droppings beneath 
them.
     Once roost entrances have been located, the bats can be 
excluded. Again, this should not be attempted when flightless 
young may be present, which usually occurs June through August 
in South Carolina. 
     Most bat species leave in winter, permitting exclusion in 
their absence. However, some bats hibernate in buildings, 
especially in warm climates, and when attics are heated. When 
this is the case, or when one does not wish to wait for winter, 
there is a relatively simple exclusion technique that can 
be used in fall, after young are flying but prior to the winter 
months.
     Inexpensive lightweight polypropylene netting can be found 
at large hardware and do-it-yourself home centers. The netting 
can be obtained in quantity to cover areas of nearly any size. 
It should be a mesh-size of 1/4 inch or smaller; 1/6 inch is 
preferred.
     Using duct tape or staples, the netting can be hung during
daylight hours above areas where bats emerge. A strip of netting 
at least two feet wide, hung one to two inches in front of bat 
exit holes, and extending at least two feet below and to the 
side of exit points, will allow the bats to emerge, but later 
they will be unable to find their way back.
     Thus, the netting acts as a simple one-way excluder until 
repairs can make the exclusion permanent. A sheet of clear, 
heavyweight plastic, also available at any hardware store, will 
have the same effect. The netting - or plastic - should be left 
in place for two to three days to assure that all bats have left 
the roost. 
     It is important to note that once bats are excluded from 
a building, they will attempt to return to the same building 
the following spring. Supplying the bats with an alternative 
roost in the form of a bat box is beneficial to the bats.
     Bat boxes are also good for homeowners, as bats are 
voracious insect consumers. Be sure the bat box is of sufficient 
size to house the displaced colony. For more information see 
"Plans for a Simple Bat House" at:
http://virtual.clemson.edu/groups/public/nsweb/nsindex.htm.
     There are other methods of bat control.
     Ineffective methods of bat control include ultrasonic 
devices and mothballs. To be at all effective, naphthalene 
flakes -- moth balls -- must evaporate rapidly, requiring 
frequent replacement. 
     Aerosol dog and cat repellents may discourage bat use 
of a particular roosting spot for periods of up to several 
months. They have also been used effectively to prevent bats 
from night roosting above porches. The spray is applied by 
day when bats are not present.
     In the case of day roosts, aerosol repellents are not 
an adequate substitute for exclusion. These repellents should 
never be applied when bats are in a roost.
     In many cases, suspending two-inch wide by seven-to-10 
inch long strips of aluminum foil or helium-filled Mylar 
balloons at a roost will deter bats. In addition, using 
bright, artificial lighting in the attic during the evening
will also discourage bats from roosting.
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     If you have gardening questions or comments, write to 
PSA Media Relations, A-101 Poole Agricultural Center, 
Clemson University, Clemson, S.C. 29634-0129. Find other 
Buds and Blooms columns under news releases, at:
http://www.clemson.edu/psamedia.
                             END