cy.
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.
INTRODUCTION
Conservation and Public Education
Despite their ecological value, bats are
relentlessly and unjustifiably persecuted. Bats
are often killed because they live near people
who needlessly fear them. These actions
emphasize the need to educate the public on
the reasons 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' Cooperative Extension Services,
universities, government environmental
conservation and health departments, and Bat
Conservation International (Austin, Texas).
Except where control is necessary, bats should
be appreciated from a distanceand not
disturbed.
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 vampire 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 following underlined bat colonial
species are found in Colorado)
The colonial species most often encountered in
and around human buildings in the United
States are the *little brown bat, (Myotis
lucifugus), the *big brown bat (Eptesicus
fuscus), the *Mexican free-tailed bat (Tadarida
brasiliensis), the pallid bat (Antrozous pallidus),
the *Yuma myotis (Myotis yumanensis), and the
evening bat (Nycticeius humeralis).
Solitary bats typically roost in tree foliage or
under bark, but occasionally are found
associated with buildings, some only as
transients during migration.
(The following underlined bat solitary
species are found in Colorado)
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 illustrations
of all bats discussed herein can be found in
Barbour and Davis (1979), Tuttle (1988),
Geluso et al. (1987), and Harvey (1986).
Any problems caused by bats are limited to
species distribution: thus animal damage
control personnel need not be concerned with
every species. Colonial and solitary bats have
BATS
Page F-2 obvious differences that serve to separate the
species into groups.
* Abridged information; only species found in
Colorado included.
Colonial Bats
Little brown bat (Myotis lucifugus)
Recognition
forearm 1.34 to 1.61 inches (3.4 to4.1 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 beyond claws.
Color
Pale tan through reddish brown to dark brown,
depending on geographic 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 cccur 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 royotis (M. yumanensis), which has
dull fur and is usually smaller. However, the
Yuma myotis and little brown may be
indistinguishable 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,
commonly roosting in dark, hot attics and
associated roof spaces where maternity
colonies may include hundreds to a few
thousand individuals. Colonies may also form
beneath shingles and siding, in tree hollows,
beneath bridges, and in caves. Litter size is 1 in
the Northeast; twins occasionally occur in some
other areas. The roost is often shared with the
big brown bat (E. fuscus) though the latter is
less tolerant of high temperatures; M. keenii
may also share the same site. Separate 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 em)
wingspan - 12.80 to 13.78 inches (32.5 to
35.0 cm)
ears - with rounded tragus
Color
From reddish brown, copper colored, to a dark
brown depending on geographic 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 roosting. Summer maternity
colonies may include a dozen or so and up to a
few hundred individuals, roosting behind
chimneys, in enclosed eaves, in hollow walls,
attics, barns, and behind shutters and unused
sliding doors. They also form colonies in rock
BATS
Page F-3 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
typically roost in smaller groups 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 familiar 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 buildings (attics, wall spaces, and
basements). 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 em); 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.
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
decomposing guano.
Confusion is not likely to occur with other
species that commonly inhabit human buildings
Habits
T. brasiliensis forms the largest colonies of any
warm-blooded animal, establishing 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
during migrations. 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 colonies, but they tend to
segregate in separate caves.
A few Taderida may 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 dimes
(largely to Mexico) for the winter.
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)
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, hybridization occurs with M.
lucifugus, mak</i>ing the species indistinguishable.
BATS
Page F-4 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 roos