are the only mammals that actually fly (flying squirrels glide).
They also have a highly developed echolocation system which allows
them to capture flying insects at night. Bats
catch insects in flight either with their mouth, wings, or tail
membranes. They usually forage from about an hour after sunset to
about an hour before sunrise, stopping to rest occasionally under
open porches, eaves, trees or other overhanging structures.
spend their days roosting in a semi-torpid state. Often bats choose
to roost in the attic or walls of occupied dwellings, posing problems
for property owners. Most colonies of bats go unnoticed, but they
may become a nuisance due to their vocalization and activity, or
odors and stains from urine, feces and rejected food. Many residents
wish to eliminate these winged mammals because they can infect humans
or pets with rabies. Only a small proportion (less than 1 percent)
of Northeastern bats are rabid. Even if rabies is confirmed from
one bat in a colony, most of the remaining animals will be healthy.
Symptoms of rabid bats include erratic flight, activity during the
daytime, and weakness or paralysis causing the bat to fall from
its roost. Most human exposure to rabies occurs when people attempt
to help grounded bats. If sick or dead bats are found, local public
health agencies should be contacted immediately.
big brown bat (Eptesicus fuscus), Eastern pipistrelle (Pipistrellus
subflavus), and four species of little brown bats (Myotis
spp.) are social bats. They usually form roost colonies during summer
in attics, barns, caves or the walls of older buildings. A colony
may consist of a few dozen up to several hundred individuals. In
winter, these bats often roost in caves or abandoned mine shafts,
but a few big brown bats may remain in attics.
species of bats in the Northeast mate promiscuously during fall.
The young of social species are born in maternity colonies during
late spring. Adult females have only one litter per year, and bear
one to two young per litter. Body heat from the colony maintains
warm temperatures for the young bats. Juveniles develop rapidly,
and are usually able to fly in about three weeks. Bats have a relatively
long life span, and may survive 10-20 years.
pesticides are currently registered for lethal control of bats in
the United States. Chemical controls may actually increase bat rabies
risks by producing sick individuals, or by driving bats from attics
into living areas. Application of pesticides may pose human health
risks because fumes or powders move to occupied floors of the building.
can homeowners do if bats decide to roost in their attics?
The only long-term control method is to batproof the home or building
in which a colony is roosting. All bats should be outside the building
before the entrance points are sealed (implement control efforts
at night). Batproofing should be attempted as soon as an unwanted
colony is detected, except during early summer when young flightless
individuals may be present. Trapped bats will soon die creating
Main access points to structures are found by observing the animals
leaving the building at dusk. Bats may enter an opening as small
as 1/4 x 1-1/2 inches. Cracks or crevices can be sealed with caulking
compound or oakum. Larger openings can be covered with metal flashing
or 1/4-inch mesh hardware wire. One primary hole should be kept
open until bats exit for the evening, then it can be temporarily
closed with a wad of aluminum foil. Trapped animals will leave the
following evening if the seal is removed at the normal exit time.
After checking for remaining individuals, the opening can be permanently
sealed. Bats will seek other entry points, so the building should
be checked each evening for several days.
Colonies in horizontal moldings or behind shutters will be discouraged
by removing the shutters or opening the molding so there are no
dark recesses. Shutters can be reattached to the home with 1-2 inch
wooden block spacers.
of lighting in roost areas will also discourage bats (install wires
properly to avoid fire hazards). The lights should be left on 24
hours a day for several weeks. Increasing ventilation to lower temperatures
may cause bats to leave in some cases.
(naphthalene or paradichlorobenzene) may repel colonies in confined
areas with poor ventilation. Recommended application rates are usually
high, and vapors could reach living areas posing a health hazard
to humans. Ultrasonic devices have not effectively repelled bats.
remove a single bat from an occupied room, turn the lights on and
open the window. Usually the bat will leave on its own without handling.
If this doesn't work, wait for the bat to land and cover it with
a coffee can. Slide cardboard under the can, and release the bat
outdoors if it has not contacted humans or pets.
bats are removed from a dwelling, any caked fecal material or crystallized
urine should be removed from flooring or beams. The odor of bat
excrement may act as a pheromone and attract other bats. The fungus
Histoplasma capsulatum can be contracted by breathing spores
in the dust of bat feces, so respirators and protective clothing
should be worn while working in bat roosts. All contaminated insulation
should also be discarded. Surfaces contaminated with urine or feces
can be disinfected by spraying with a solution of 1 part bleach/20
parts tap water. Deodorants can then be applied to mask any remaining
summary, bats are beneficial because they eat large numbers of insects.
Excluding bats from structures will be the most practical type of
from Paul D. Curtis, Department of Natural Resources, Cornell University,