Build Bat Boxes

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Diagram shows the first of two proposed bat box designs.
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The second of two bat box designs.
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Use of pesticides such as DDT and other misguided eradication efforts have diminished the bat population, in some species to the edge of extinction. Bat boxes are one proposed solution to help them recover.

People who reside near rivers, swamps, lakes, or ponds can
usually expect high insect populations. But, if they’re
lucky, such folks will discover that the bugs are kept in
check by local colonies of bats … which swoop out of
their roosts each evening and locate their pesky prey with
remarkably precise “radar” systems (echoes of their
high-pitched squeaks return to them whenever the sound
waves encounter solid objects). During the summer months,
bat colonies consume mosquitoes, gnats, moths, and beetles,
thereby playing essential roles in the ecosystem. In fact,
some of the little predators eat as much as half their
body weight in insects each night!

A War of Ignorance

Unfortunately, however, these nocturnal hunters aren’t seen
in the night skies as often as they were some 35 years ago because they’ve suffered, as many insectivorous (and
other!) birds have, from the effects of DDT. And though
this deadly pesticide has been banned from general use in
the United States since 1972, it’s sometimes still,
illegally, dumped into attics as “bat control” (although
the poison probably endangers the human occupants
of treated residences almost as much as it does the winged
population it’s meant to kill or evict).

Furthermore, as if residual DDT (and the continuing
“outlaw” use of the chemical) in the United States weren’t
bad enough, bats have no awareness of national borders. The Carlsbad
Caverns’ bat population decreased from an estimated 8.7
million in 1936 to 200,000 in 1973, and is still being
reduced as a result of the mammals’ annual migration to
Mexico, where DDT is still in regular use.

While many bats fall to such poisons, others are prey to
the deeply ingrained fears and misunderstandings of humans
who wantonly destroy their roosts or carelessly disturb the
animals in their hibernation caves. The latter action can
be particularly harmful, because — when hibernating
— bats fall into a deep torpor and live off small
reserves of stored fat. If they’re aroused unnecessarily,
the animals use up their “rations” too rapidly, and may
well starve in their sleep before the spring awakening.

So far, three bat varieties are on the U.S. endangered
species list, two more have been proposed for listing, and still others are probably in need of protection.
(Being on the list doesn’t insure the survival of a
species, but does provide some habitat protection.) Bats
that may shortly become extinct are the Indiana (
Myotis sodalis ), the Gray ( Myotis
), the Hawaiian Hoary ( Lasiurus
cinereus semotus
), the Virginia Big-Eared (
Plecotus townsendii virginianus ), and the Ozark
Big-Eared ( Plecotus townsendii ingens ).

“Bad Press” Victims

In the Western world, bats — although they are, for
the most part, harmless and may well be the most
effective natural insect controls in existence — have
long been feared. This human reaction probably stems from
the fact that medieval artists often attached bat wings to
figures representing devils and demons … as well, of
course, as from the animals’ connection with the Dracula

Other cultures, however, have long recognized how important
the tiny mammals are to the planet’s health. Pre-Columbian
societies, both in Mexico and in Central America,
celebrated the winged wonders in their religions and
represented them in their artifacts … and — in
the East — bats are considered good omens and symbols
of longevity. (Though most small mammals have short life
spans, one bat is on record as having survived 30 years in
the wild.)

The fact is, nearly everything most folks “know” about bats
is wrong. The animals don’t get in people’s hair, aren’t aggressive, blind, or dirty, and have a
relatively low incidence of rabies. Just keep in mind that
they’re extremely shy and intolerant of disturbances, so
healthy bats are very difficult to catch. Those
that can be approached are probably sick and should be
handled by experts or with great caution, because —
like most wild animals — bats will bite when

Of course, sick animals may simply be victims of chemical
poisons. DDT, for example, disperses the animals from their
roosts, makes them ill, and often causes their deaths far
from the site of their poisoning. Furthermore, any
survivors of DDT spraying will be especially
susceptible to all kinds of viruses, including

You Can Help

In order to encourage the establishment of new bat
colonies, an experimental project to provide special roosts
has been begun by the Center for Action on Endangered
Species. Artificial “bat caves” have already been used
successfully in Europe, but they’re entirely new in this
country. The Center has come up with designs for bat boxes  that are simple to
make out of inexpensive, rough, untreated wood. (Some
Europeans have had success with painted boxes, but others
feel that paint odors discourage habitation. This question
won’t be answered until more information is available, and
you can help provide such data by putting up both
painted and unpainted versions, and observing the

The box’s exact shape and size probably aren’t important,
but the width of the entry shouldn’t exceed one inch (3/4
inch is ideal). Bats can get through very small
spaces, and the use of a narrow opening will discourage
other creatures from moving in. Also, the dwelling should
be as tightly constructed as possible, because young bats
grow best where daytime temperatures are in the 80-90°F
range, and in environments where their body warmth is well

Very little is yet known about bats’ preferences as to the
location of the boxes, but — according to the
information now available — the best bet is to fasten
them 12 to 15 feet off the ground on a building or tree
trunk. (A “managed” forest, where undergrowth has been
removed, is most likely a good area to place a “house”.)
Make sure, too, that the roosts are positioned in such a
way that they’ll receive morning sun and afternoon shade,
since inside temperatures above 90°F will be
pretty much intolerable to your hoped-for guests. In
addition, most bats seem to prefer sites that are
relatively well protected from the wind, and — of
course — your boxes will be attractive only
if located in areas with heavy populations of flying bugs.

Do It Now!

After a summer of feeding, bats mate and hibernate in the
fall, with the females storing the sperm over the winter.
Once insects become available again, one or more babies
(according to the species) are born and suckled for the two
weeks it takes them to learn to fly. (The males move out
while the young are being reared.)

In order to attract bat mothers, install your boxes by
early April. Sometimes you can expect guests within a few
weeks after putting up the shelters, but they may take a
year or more to make use of the proffered housing.

By reporting your successes and failures, you can
contribute to the small — but growing — store
of bat knowledge … and maybe help to preserve these
worthy little animals. Bat-box experimenters can obtain a
free reporting form, along with additional bat information,
from the Center for Action on Endangered Species.

Let’s face it — in comparison to work being done on
behalf of whales, elephants, great cats, and crocodiles
— bat preservation may not seem very glamorous. But
humankind desperately needs these marvelous little mammals,
and our misunderstood bats can certainly use some friends.
Won’t you be one?