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United States Department of Agriculture
Bureau of Biological Survey

Washington, D. C. x | -------- April 1935

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INSTRUCTIONS FOR CONTROLLING BATS

Prepared in the Section of Predator and Rodent Control
Division of Game Management

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Bats are almost entirely beneficial, but complaints against them are
made largely because of the results of their roosting in homes and other oc-—
cupicdspurldings. The objection to their presence is due in part also to an
aversion that many people have to them, just as they have to snakes, spiders,
and rats, but more because of the highly objectionable odor that is always
asscciated with a roost of bats. This pungent, penetrating odor comes from
their droppings and urine, which collect rapidly under their roosts and make
it necessary to drive them away, to shut them out, or, as a last resort, to
kill them. The following control methods are suggested:

It is frequently possible, by the use of naphthalene, to drive bats from
their congregating places in attics, double walls, or other enclosed spaces that
afford suitable roosting sites. The naphthalene can be purchased at local drug
stores either in the flake form or as common "moth balls." The flakes, which
are preferable for this purpose, should be thrown liberally around the places
occupied. Usually 2 to 5 pounds are required to drive the bats from the average
roost in a building. The treatment should be repeated after a week if neces-—
sary. The odor of the naphthalene is so objectionable to bats that usually
they will leave the premises where it is used.

Bats can sometimes be shut out of an established roost in a building,
though this is often difficult, as there are usually many openings through
which they can gain entrance. They can be excluded, however, by finding and
Closing all the openings they use. In blocking such openings, at least one
should be left open until after dark, when the bats leave on their nightly
search for food. After all the bats are out, the remaining openings should be
closed.

Fumigation with calcium cyanide has been effective in destroying the
roosts by killing the bats. The gas generated, however, is so deadly that ex-
treme care must be used to avoid endangering human life. The odors created by
the bats thus killed also are objectionable. Calcium cyanide in dust or granu-
lar form should be inserted into the cavities occupied by the bats. Because of
the danger of using the cyanide, however, this method should not be employed
when the use of naphthalene as a repellent will answer the purpose or when the
bats can be shut out of a building as above described.

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