D-5

BATS

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994

Coop erat ive Extension Division

Institute of Agriculture and Natural Resources

University of Nebraska - Lincoln

United States Department of Agriculture

Animal and Plant Health Inspection Service

Animal Damage Control

Great Plains Agricultural Council

Wildlife Committee

Damage Prevention and

Control Methods

Exclusion

Polypropylene netting checkvalves

simplify getting bats out.

Quality bat-proofing permanently

excludes bats.

Initiate control before young are born

or after they are able to fly.

Repellents

Naphthalene: limited efficacy.

Illu mination.

Air drafts/ventilation.

Ultrasonic devices: not effective.

Sticky deterrents: limited efficacy.

Toxicants

None are registered.

Trapping

Available, but unnecessarily

complicated compared to exclusion

and bat-proofing.

Other Methods

Sanitation and cleanup.

Artificial roosts.

Removal of Occasional Bat

Intruders

When no bite or contact has occurred,

help the bat escape (otherwise

submit it for rabies testing).

Conservation and Public Education

Information itself functions as a

management technique.

Arthur M. Greenhall

Research Associate

Department of Mammalogy

American Museum of Natural History

New York, New York 10024

Stephen C. Frantz

Vertebrate Vector Specialist

Wadsworth Center for Laboratories

and Research

New York State Department of Health

Albany, New York 12201-0509

Fig. 1. Little brown bat, Myotis lucifugus

D-6

Introduction

Conservation and Public Education

Despite their ecological value, bats are

relentlessly and unjustifiably perse-

cuted. Bats are often killed because

they live near people who needlessly

fear them. These actions emphasize the

need to educate the public on the rea-

sons for bat conservation and why it is

important to use safe, nondestructive

methods to alleviate conflicts between

people and bats. General sources of

information on bats include states’

Coop erative Extension S ervices, uni-

versities, government environmental

conservation and health departments,

and Bat Conservation International

(Austin, Texas). Except where control

is necessary, bats should be appreci-

ated from a distance — and not dis-

turbed.

Identification and Range

Bats, the only mammals that truly fly,

belong to the order Chiroptera. Their

ability to fly, their secretiveness, and

their nocturnal habits have contributed

to bat folklore, superstition, and fear.

They are worldwide in distribution

and include about 900 species, second

in number only to Rodentia (the

rodents) among the mammals.

Among the 40 species of bats found

north of Mexico, only a few cause

problems for humans (note that vam-

pire bats are not found in the United

States and Canada). Bats congregating

in groups are called colonial bats;

those that live a lone existence are

known as solitary bats.

The colonial species most often en-

countered in and around human

buildings in the United States are the

little brown bat, (Myotis lucifugus, Fig.

2), the big brown bat (Eptesicus fuscus,

Fig. 3), the Mexican free-tailed bat

(Tadarida brasiliensis, Fig. 4), the pallid

bat (Antrozous pallidus), the Yuma

myotis (Myotis yumanensis), and the

evening bat (Nycticeius humeralis).

Solitary bats typically roost in tree foli-

age or under bark, but occasionally are

found associated with buildings, some

only as transients during migration.

Fig. 2. Little brown bat, Myotis lucifugus

Fig. 3. Big brown bat, Eptesicus fuscus

D-7

Fig. 5. Anatomy of a typical bat

Wrist

Ear

Tragus

Upper arm

Forearm

Thumb

Second

finger

Third

finger

Fourth finger

Fifth finger

Wing membrane

Foot

Calcar

Knee

Tail

membrane

These include Keen’s bat (Myotis

keenii), the red bat (Lasiurus borealis),

the silver-haired bat (Lasionycteris

noctivagans), and the hoary bat

(Lasiurus cinereus). Excellent illustra-

tions of all bats discussed herein can be

found in Barbour and Davis (1979),

Tuttle (1988), Geluso et al. (1987), and

Harvey (1986).

Several species of bats have been

included here, with significant inter-

specific differences that need to be

clarified if well-planned, comprehen-

sive management strategies are to be

developed. Any problems caused by

bats are limited to species distribution;

thus animal damage control personnel

need not be conc erned with every spe-

cies.

Colonial and solitary bats have obvi-

ous differences that serve to separate

the species into groups (refer to Fig. 5).

Much of the descriptive material that

follows is adapted from Barbour and

Davis (1979).

Fig. 4. Mexic an free-tailed bat, Tadarida brasiliensis

D-8

Colonial Bats

Little brown bat (Myotis lucifugus)

Recognition

forearm — 1.34 to 1.61 inches (3.4 to

4.1 cm)

wingspan — 9.02 to 10.59 inches (22.9

to 26.9 cm)

ears — 0.55 to 0.63 inches (1.4 to 1.6

cm)

foot — approximately 0.39 inches (1.0

cm); long hairs on toes extend be-

yond claws.

Distribution (Fig. 6a)

Color

Pale tan through reddish brown to

dark brown, depending on geo-

grap hic location. The species is a

rich dark brown in the eastern

United States and most of the west

coast. Fur is glossy and sleek.

Confusion may occur with a few other

“house” bat species. In the East, it

may be confused with Keen’s bat

(M. keenii), which has longer ears

[0.69 to 0.75 inches (1.7 to 1.9 cm)]

and a longer, more pointed tragus

(the appendage at the base of the

ear). In the West, it resembles the

Yuma myotis (M. yumanensis),

which has dull fur and is usually

smaller. However, the Yuma myotis

and little brown may be indistin-

guishable in some parts of the

northwestern United States where

they may hybridize.

Habits

This is one of the most common bats

found in and near buildings, often

located near a body of water where

they forage for insect prey. Summer

colonies are very gregarious, com-

monly roosting in dark, hot attics

and associated roof spaces where

maternity colonies may include

hundreds to a few thousand indi-

viduals. Colonies may also form

beneath shingles and siding, in tree

hollows, beneath bridges, and in

caves. Litter size is 1 in the North-

east; twins occasionally occur in

some other areas. The roost is often

shared with the big brown bat (E.

fuscus) though the latter is less toler-

ant of high temperatures; M. keenii

may also share the same site. Sepa-

rate groups of males tend to be

smaller and choose cooler roosts

within attics, behind shutters, under

tree bark, in rock crevices, and

within caves.

In the winter, little brown bats in the

eastern part of their range abandon

buildings to hibernate in caves and

mines. Such hibernacula may be

near summer roosts or up to a few

hundred miles (km) away. Little is

known of the winter habits of M.

lucifugus in the western United

States.

The life span of little brown bats has

been established to be as great as 31

years. The average life expectancy,

however, is probably limited to only

a few years.

Big brown bat (Eptesicus fuscus)

Recognition

forearm — 1.65 to 2.01 inches (4.2 to

5.1 cm)

wingspan — 12.80 to 13.78 inches (32.5

to 35.0 cm)

ears — with rounded tragus

Distribution (Fig. 6b)

Color

From reddish brown, copper colored,

to a dark brown depending on geo-

grap hic location. This is a large bat

without distinctive markings.

Confusion may occur with the evening

bat (Nycticeius humeralis) though the

latter is much smaller.

Habits

This hardy, rather sedentary species

appears to favor buildings for roost-

ing. Summer maternity colonies

may include a dozen or so and up

to a few hundred individuals, roost-

ing behind chimneys, in enclosed

eaves, in hollow walls, attics, barns,

and behind shutters and unused

sliding doors. They also form colo-

nies in rock crevices, beneath

bridges, in hollow trees, and under

loose bark. Litter size is 2 in the East

to the Great Plains; from the

Rockies westward 1 young is born.

E. fuscus frequently shares roosts

with M. lucifugus in the East, and

with M. yumanensis, Taderida, and

Antrozous in the West. Males typi-

cally roost in smaller group s or

alone during the summer.

The big brown bat is one of the most

widely distributed of bats in the

United States and is probably famil-

iar to more people than any other

species. This is partially due to its

large, easy-to-observe size, but also

to its ability to overwinter in build-

ings (attics, wall spaces, and base-

ments). Its close proximity to

humans, coupled with its tendency

to move about when temperature

shifts occur, often brings this bat

into human living quarters and

basements in summer and winter.

Big browns also hibernate in caves,

mines, storm sewers, burial vaults,

and other underground harborage.

While E. fuscus will apparently

travel as far as 150 miles (241 km) to

hibernacula, the winter quarters of

the bulk of this species are largely

unknown.

Big brown bats may live as long as 18

years.

Mexican free-tailed bat (Tadarida

brasiliensis)

Recognition

forearm — 1.42 to 1.81 inches (3.6 to

4.6 cm)

wingspan — 11.42 to 12.80 inches (29.0

to 32.5 cm); long narrow wings

tail (interfemoral) membrane — does

not enclose the lower one-third to

one-half of the tail, hence the name

free-tailed

foot — long, stiff hairs as long as the

foot protrude from the toes.

Distribution (Fig. 6c)

Color

Dark brown or dark gray. Fur of some

individuals may have been

bleached to a pale brown due to

ammonia fumes from urine and de-

composing guano.

Confusion is not likely to occur with

other species that commonly inhabit

human buildings.

D-9

Habits

T. brasiliensis forms the largest colonies

of any warm-blooded animal, estab-

lishing sizable colonies in buildings,

particularly on the West Coast and

in the Gulf states from Texas east.

Hundreds to thousands may be

found in buildings or under

bridges. It is primarily a cave bat in

Arizona, New Mexico, Oklahoma,

and Texas; buildings are used as

temporary roosts du ring migra-

tions. Litter size is 1.

Taderida often share roosts with other

species. In the West, for example,

they may be found in buildings

with A. pallidus, M. yumanensis, and

E. fuscus. Some males are always

present in the large maternity colo-

nies, but they tend to segregate in

separate caves.

A few Taderida m ay overwinter in

buildings as far north as South

Carolina in the East and Oregon in

the West. Most of this species

migrate hundreds of miles to

warmer climes (largely to Mexico)

for the winter.

Pallid bat (Antrozous pallidus)

Recognition

forearm — 1.89 to 2.36 inches (4.8 to

6.0 cm)

wingspan — 14.17 to 15.35 inches (36.0

to 39.0 cm)

ears — large; widely separated and

more than half as broad as long.

The ears are nearly half as long as

the combined length of the bat’s

head and body.

eyes — large

Distribution (Fig. 6d)

Color

pale, upp er parts are light yellow, the

hairs tipped with brown or gray.

Underparts are pale creamy, almost

white. This large, light-colored bat

is relatively easy to recognize.

Confusion with other species that com-

monly inhabit human buildings is

not likely to occur.

Habits

Maternity colony size ranges from

about 12 to 100 individuals. Roost

sites include buildings, bridges, and

rock crevices; less frequently, tree

cavities, caves, and mines. Litter

size is most commonly 2. The roost

is frequently shared with T.

brasiliensis and E. fuscus in the West.

While groups of males tend to seg-

regate during the nursery period

(sometimes in the same building),

other males are found within the

maternity colony.

An interesting feature of pallid bats is

that they fly close to the ground,

may hover, and take most prey on

the ground, not in flight. Prey

includes crickets, grasshoppers,

beetles, and scorpions. They will

also forage among tree foliage.

Pallid bats are not known to make long

migrations, though little is known

of their winter habits.

Yuma myotis (Myotis yumanensis)

Recognition

forearm — 1.26 to 1.50 inches (3.2 to

3.8 cm)

wingspan — about 9.25 inches (23.5

cm)

ears — 0.55 to 0.59 inches (1.4 to 1.5 cm)

foot — 0.39 inches (1.0 cm)

Distribution (Fig. 6e)

Color

Light tan to dark brown; underside is

whitish to buffy.

Confusion may occur in the West with

M. lucifugus, though the latter tends

to have longer, glossier fur, and is

larger. In the Northwest, hybridiza-

tion occurs with M. lucifugus, mak-

ing the species indistinguishable.

Habits

Maternity colonies, up to several

thousand individuals, form in the

summer in attics, belfries, under

bridges, and in caves and mines.

Litter size is 1. Males typically

segregate during the nursery period

and roost as solitary individuals in

buildings and other suitable harbor-

age.

M. yumanensis is more closely associ-

ated with water than is any other

North American bat species. Nearly

all roosts have open water nearby.

This species is not as tolerant as M.

lucifugus of high roost temperatures

and will move to cooler niches

within a building when tempera-

tures rise much above 100

o

F

(37.8

o

C).

M. yumanensis abandons maternity

colonies in the fall, but its winter

habitat is not known.

Evening bat (Nycticeius humeralis)

Recognition

forearm — 1.30 to 1.54 inches (3.3 to

3.9 cm)

wingspan — 10.24 to 11.02 inches (26.0

to 28.0 cm)

ears — with short, curved, and

rounded tragus

Confusion may occur with the big

brown bat (E. fuscus), which can be

readily distinguished by its larger

size. It bears some resemblance to

the somewhat smaller little brown

bat (M. lucifugus) but can be identi-

fied by its characteristic blunt

tragus.

Distribution (Fig. 6f)

Color

Medium brown with some variation to

yellow-brown in subtropical

Florida. No distinctive markings.

Habits

Summer maternity colonies in build-

ings may consist of hundreds of

individuals. Litter size is usually 2.

Colonies also form in tree cavities

and under loose tree bark. In the

Southeast, T. brasiliensis commonly

inhabits the same building with N.

humeralis. This is one of the most

common bats in towns throughout

the southern coastal states. Very

little is known about this species,

and virtually nothing is known of

its winter habitat except that it

almost never enters caves.

D-10

Solitary Bats

Keen’s bat (Myotis keenii)

Recognition

forearm — 1.26 to 1.54 inches (3.2 to

3.9 cm)

wingspan — 8.98 to 10.16 inches (22.8

to 25.8 cm)

ears — 0.67 to 0.75 inches (1.7 to 1.9 cm);

with a long, narrow, pointed tragus

Distribution (Fig. 6g)

Color

Brown, but not glossy; somewhat paler

in the East.

Confusion may occur with M.

lucifugus, which has glossy fur,

shorter ears, and does not have the

long, pointed tragus.

Habits

Excluding small maternity colonies (up

to 30 individuals are on record), M.

keenii are generally found singly in the

East. Roosting sites include: behind

shutters, under wooden shingles, shel-

tered entryways of buildings, in roof

spaces, in barns, and beneath tree

bark. In the West, this bat is known as

a solitary species, roosting in tree cavi-

ties and cliff crevices. Litter size is

probably 1. The roost is sometimes

shared with M. lucifugus. The sexes

probably segregate during the nurs-

ery period. In winter, these bats hiber-

nate in caves and mines.

Red Bat (Lasiurus borealis)

Recognition

forearm — 1.38 to 1.77 inches (3.5 to

4.5 cm)

wingspan — 11.42 to 13.07 inches (29.0

to 33.2 cm); long, pointed wings

ears — short rounded

tail membrane — heavily furred on

upper surface, with a distinctive

long tail.

Distribution (Fig. 6h)

Color

Bright orange to yellow-brown; usu-

ally with a distinctive white mark

on the shoulders.

Confusion may occur with the hoary

bat (L. cinereus), which is frosted-

gray in appearance and larger.

Habits

Red bats live solitary lives, coming

together only to mate and migrate.

Few people are familiar with this spe-

cies. They typically spend summer

days hidden in the foliage of decidu-

ous trees. The number of young ranges

from 1 to 4, averaging 2.3.

These bats often chase insects that are

attracted to lights, such as street

lamp s. It is this behavior that most

likely brings them in close proxim-

ity to peop le.

L. borealis is well-adapted for surviving

drastic temperature fluctuations; it

does not hibernate in caves, but

apparently in trees. Some migrate

long distances. During migration,

red bats have been known to land

on high-rise buildings and on

ships at sea.

Silver-haired bat (Lasionycteris

noctivagans)

Recognition

forearm — 1.46 to 1.73 inches (3.7 to

4.4 cm)

wingspan — 10.63 to 12.20 inches (27.0

to 31.0 cm)

ears — short, rounded, hairless

tail membrane — up per surface is

sparsely furred on the anterior one-

half.

Distribution (Fig. 6i)

Color

Usually black with silver-tipped fur;

some individuals with dark brown,

yellowish-tipped fur.

Confusion sometimes occurs with the

larger hoary bat (Lasiurus cinereus),

which has patches of hair on the ears

and wings, heavy fur on the entire

upper surface of the tail membrane,

and has a distinctive throat “collar.”

Habits

The silver-haired bat roosts in a wide

variety of harborages. A typical

roost might be behind loose tree

bark; other sites include tree hol-

lows and bird nests. This species is

solitary excep t when with young.

Additionally, there are unconfirmed

reports that it is sometimes colonial

(Dalquest and Walton 1970) and

may roost in and on buildings. The

litter size is 2. The sexes segregate

through much of the summer range.

L. noctivagans hibernates in tree crevices,

under loose bark, in buildings

(including churches, sky scrapers, and

wharf houses), hulls of ships, rock

crevices, silica mines, and non-

limestone caves. It also may migrate,

during which time it is encountered

in buildings (they favor open sheds,

garages, and outbuildings rather than

enclosed attics), in lumber piles,

and on ships at sea.

Hoary bat (Lasiurus cinereus)

Recognition

forearm — 1.81 to 2.28 inches (4.6 to

5.8 cm)

wingspan — 14.96 to 16.14 inches (38.0

to 41.0 cm)

ears — relatively short, rounded,

edged with black, and with fur

tail membrane — completely furred on

upper surface

Distribution (Fig. 6j)

Color

Dark, but many hairs are tipped in

white, giving it a frosted appear-

ance. This bat also has a yellowish

or orangish throat “collar.”

Confusion may sometimes occur with

the much smaller silver-haired bat

(Lasionycteris noctivagans), which

lacks the fur patches and markings

on the ears, markings on the throat,

and has a tail membrane that is only

lightly furred on the upper surface.

Habits

Hoary bats generally spend summer

days concealed in tree foliage (often

in evergreens), rarely enter houses,

and are not commonly encountered

by people. L. cinereus at their day

roosts are usually solitary except

when with young. The litter size is

2. The sexes segregate through most

of the summer range.

This is one of the largest bats in North

America, a powerful flier, and an

accomplished migrant. Records

indicate that some L. cinereus may

hibernate in northern parts of their

range.

D-11

j

g

h

i

Figure 6. Distributions of selected bat species in North America:

(a) little brown bat, (b) big brown bat, (c) Mexican free-tailed bat,

(d) pallid bat, (e) Yuma myotis, (f) evening bat, (g) Keen’s bat,

(h) red bat, (i) silver-haired bat, (j) hoary bat.

b

c

a

d

e

f

D-12

Modification and destruction of roost

sites has also decreased bat numbers.

Sealing and flooding of mineshafts and

caves and general quarrying opera-

tions may inadvertently ruin bat har-

borages. Forestry practices have

reduced the number of hollow trees

available. Some of the elimination of

natural bat habitat may contribute to

bats roosting in buildings.

Damage and Damage

Identification

Bat Presence

Bats often fly about swimming pools,

from which they drink or catch insects.

White light (with an ultraviolet com-

ponent), commonly used for porch

lights, building illumination, street and

parking-lot lights, may attract flying

insects, which in turn attract bats.

Unfortunately, the mere presence of a

bat outdoors is sometimes beyond the

tolerance of some uninformed people.

Information is a good remedy for such

situations.

Bats commonly enter buildings

through openings associated with the

roof edge and valleys, eaves, apex of

the gable, chimney, attic or roof vent,

dormers, and siding (see Fig. 7). Other

Food Habits

Bats in North America are virtually all

insectivorous, feeding on a variety of

flying insects (exceptions among house

bats were noted previously). Many of

the insects are harmful to humans.

While there must be some limitations

based on such factors as bats’ body

size, flight capabilities, and jaw open-

ing, insectivorous bats apparently con-

sume a wide range of prey (Barbour

and Davis 1979). The little brown bat’s

diet includes mayflies, midges, mos-

quitoes, caddis flies, moths, and

beetles. It can consume insects equal to

one-third of its body weight in 1/2

hour of foraging. The big brown bat

may fill its stomach in about 1 hour

(roughly 0.1 ounce per hour [2.7 g/hr])

with prey including beetles, moths, fly-

ing ants, true bugs, mayflies, caddis

flies, and other insects. The nightly

consumption of insects by a colony of

bats can be extremely large.

General Biology,

Reproduction, and

Behavior

Most North American bats emit high

frequency sounds (ultrasound) inau-

dible to humans and similar to sonar,

in order to avoid obstacles, locate and

capture insect prey, and to communi-

cate. Bats also emit audible sounds

that may be used for communication

between them.

Bats generally mate in the fall and win-

ter, but the female retains the sperm in

the uterus until spring, when ovulation

and fertilization take place. Pregnant

females may congregate in maternity

colonies in buildings, behind chim-

neys, beneath bridges, in tree hollows,

caves, mines, or other dark retreats.

No nests are built. Births typically

occur from May through July. Young

bats grow rapidly and are able to fly

within 3 weeks. Weaning occurs in

July and August, after which the

nursery colonies disperse.

Bats prepare for winter around the

time of the first frost. Some species

migrate relatively short distances,

whereas certain populations of the

Mexican free-tailed bat may migrate

up to 1,000 miles (1,600 km). Bats in

the northern United States and Canada

may hibernate from September

through May. Hibernation for the

same species in the southern part of

their range may be shorter or even

sporadic. S ome may fly during warm

winter sp ells (as big brown bats may in

the northeastern part of the United

States). Bats often live more than 10

years.

In response to a variety of human

activities, direct and indirect, several

bat species in the United States have

declined in number during the past

few decades. Chemical pesticides (par-

ticularly the use of persistent and

bioaccumulating organic pesticides)

have decreased the insect supply, and

contaminated insects ingested by bats

have reduced bat populations. Many

bats die when people disturb summer

maternity roosts and winter hiber-

nacula. Vandals and other irrespon-

sible individuals may deliberately kill

bats in caves and other roosts. Even

the activities of speleologists or biolo-

gists may unintentionally disturb

hibernating bats, which depletes fat

reserves needed for hibernation.

Fig. 7. Common points of entry and roosting sites of house bats.

Drip edge

Under

porch

roof

Under siding

Under ro ofing Ridge cap

Fascia boards

Chimney flue

Between ho use & chimney

Flashing

Vent Soffits Hollow walls

Rafters

D-13

openings may be found under loose-

fitting doors, around windows, gaps

around various conduits (wiring,

plumbing, air conditioning) that pass

through walls, and through utility

ven ts.

Bats are able to squeeze through nar-

row slits and cracks. For purposes of

bat management, one should pay

attention to any gap of approximately

1/4 x 1 1/2 inches (0.6 x 3.8 cm) or a

hole 5/8 x 7/8 inch (1.6 x 2.2 cm). Such

openings must be considered potential

entries for at least the smaller species,

such as the little brown bat. The

smaller species require an opening no

wider than 3/8 inch (0.95 cm), that is, a

hole the diameter of a US 10-cent coin

(Greenhall 1982). Openings of these

dimensions are not uncommon in

older wood frame structures where

boards have shrunk, warped, or other-

wise become loosened.

The discovery of one or two bats in a

house is a frequent p roblem. In the

Northeast, big brown bats probably

account for most sudden appearances

(see Figs. 3 and 8). Common in urban

areas, they often enter homes through

open windows or unscreened fire-

places. If unused chimneys are selected

for summer roosts, bats may fall or

crawl through the open damper into

the house. Sometimes bats may appear

in a room, then disappear by crawling

under a door to another room, hall-

way, or closet. They may also disap-

pear behind curtains, wall hangings,

bookcases, under beds, into waste bas-

kets, and so forth. Locating and

removing individual bats from living

quarters can be laborious but is

important. If all else fails, wait until

dusk when the bat may appear once

again as it attempts to find an exit.

Since big brown bats may hibernate in

the cooler recesses of heated buildings,

they may suddenly appear (flying

indoors or ou tdoors) in midwinter

during a warm spell or a cold snap as

they move about to adjust to the tem-

perature shift.

Roosting Sites

Bats use roosting niches that are

indoors (human dwellings, outbuild-

ings, livestock quarters, warehouses),

semi-enclosed (loading docks, entrance

foyers), partially sheltered (porches,

carports, pavilions, highway under-

passes, bridges), and open structural

areas (window shutters, signs). Once

there, active bats in and on buildings

can have several economic and aes-

thetic effects, often intertwined with

public health issues (Frantz, 1988).

Unusual roosting areas include wells,

sewers, and graveyard crypts. Before

considering control measures, verify

that bats are actually the cause of the

problem.

Rub Marks

Surface areas on walls, under loose

woodwork, between bricks and

around other bat entryways often have

a smooth, polished appearance. The

stained area is slightly sticky, may con-

tain a few bat hairs, and is yellow-

brown to blackish brown in color. The

smooth gloss of these rub marks is due

to oils from fur and other bodily secre-

tions mixed with dust, deposited there

as many animals pass repeatedly for a

long p eriod over the same surface.

Openings marked in this way have

been used heavily by bats.

Noise

Disturbing sounds may be heard from

vocalizations and grooming, scratch-

ing, crawling, or climbing in attics,

under eaves, behind walls, and

between floors. Bats become particu-

larly noisy on hot days in attics, before

leaving the roost at dusk, and upon

returning at dawn. Note that rustling

sounds in chimneys may be caused by

birds or raccoons and scratching and

thumping sounds in attics and behind

walls may indicate rats, mice, or

squirrels.

Guano and Urine

Fecal pellets indicate the presence of

animals and are found on attic floors,

in wall recesses, and outside the house

at its base. Fecal pellets along and

inside walls may indicate the presence

of mice, rats, or even roaches. Since

most house bats north of Mexico are

insectivorous, their droppings are

easily distinguished from those of

small rodents. Bat droppings tend to

be segmented, elongated, and friable.

When crushed, they become powdery

and reveal shiny bits of undigested

insect remains. In contrast, mice and

rat droppings tend to taper, are

unsegmented, are harder and more

fibrous, and do not become powdery

when crushed (unless ex tremely aged).

The droppings of some birds and liz-

ards may occasionally be found along

with those of bats. However, bat drop-

pings never contain the white chalky

material characteristic of the feces of

these other animals.

Bat excrement produces an unpleasant

odor as it decomposes in attics, wall

spaces, and other voids. The pungent,

musty, acrid odor can often be

detected from outside a building con-

taining a large or long-term colony.

Similar odor problems occur when ani-

mals die in inaccessible locations. The

odor also attracts arthropods which

may later invade other areas of a

building.

Bat guano may provide a growth

medium for microorganisms, some of

which are pathogenic (histoplasmosis,

for example) to humans. Guano accu-

mulations may fill spaces between

walls, floors, and ceilings. It may cre-

ate a safety hazard on floors, steps,

and ladders, and may even collapse

ceilings. Accumulations also result in

the staining of ceilings, soffits, and sid-

ing, producing unsightly and

unsanitary c