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Bat Biology
Bats belong to the order Chiroptera, which
means "handwing" They are the only mammal that can truly
fly. Florida has 13 resident bat species. Contrary to popular
belief, bats are not blind. Their vision is adapted for
low light levels. However, bats can maneuver in complete
darkness using echolocation.
Echolocation is the use of sound waves to detect objects.
Bats emit high pitched sounds and listen for them to echo
back. The length of time it takes the echo to return tells
the bat how far away it is from an object. This allows the
bat to fly in the dark and hunt for food. Bats’ feet are
uniquely adapted for grasping structures so that they can
rest while hanging upside down. Bats undergo a state of
torpor in the daytime; their heart rate and body temperature
decrease so that they can conserve energy. Because of this,
bats are reluctant to fly in the daytime even when disturbed.
If they are forced to fly, they must first raise their body
temperature and heart rate.
For their size, bats have the longest lifespan of any mammal.
Some can live for more than thirty years.
Diet
Florida’s native bats are insectivorous,
meaning they eat insects including beetles, mosquitoes,
moths, and other agriculture and garden pests. In fact,
bats are the most important controller of night flying insects
because a single bat can eat up to 3,000 insects a night!
Habitat
Some bats, like the Brazilian free-tailed
bat, the evening bat, and the big brown bat are colonial
meaning they gather together in a colony to roost during
the day. Colonial bat habitats include cracks, crevices,
hollows of trees, caves, and manmade structures including
buildings, bridges, tile roofs, and bat houses. Other species
in Florida are solitary and live in dead fronds of palm
trees, Spanish moss, and tree foliage.
Reproduction
In Florida, bats mostly mate in the fall
and winter. The female does not usually ovulate until the
spring when the insect population increases, but she can
retain sperm for months before ovulation occurs. Most female
bats only have one pup per year. For their size, bats are
the slowest reproducing mammals. Pregnant females of some
species will gather together in nursery colonies. Bats do
not build nests. They normally give birth from mid-April
through July, and their young begin to fly within 3 to 6
weeks. Juveniles are then weaned from their mothers and
by mid-August the young are able to forage and fly on their
own. Bats will not reach reproductive maturity until they
are about one year old. This is considerably longer than
most small mammals.
Bats and People
Bat populations are declining in many areas.
The loss of roosting sites (such as trees and caves) can
cause bats to roost in areas where they are more likely
to become a nuisance for people. The use of pesticides to
control insects can take away the food that bats eat, and
sometimes poison the bats themselves. These unique mammals
have been sensationalized in the news and horror movies,
creating a great deal of anxiety among Americans. Fear of
rabid bats has caused mass destruction of bat populations
for decades even though they seldom pose public health problems.
Ironically, this fear has caused more people to come in
contact with bats while attempting to eradicate them! Rabies,
a virus usually transmitted from a bite, affects a very
small portion of the bat population in Florida. Histoplasmosis
is a respiratory illness caused by a fungus. This fungus
is found in soil that is enriched with bat or bird feces.
This fungus is sometimes found on chicken farms or in caves.
According to the Florida Bat Conservancy, "this illness
has been associated with bats in Florida in only a few cases,
all of which involved visits to bat caves" Attics and roofs
are normally dry areas that do not provide the proper conditions
for this fungus to survive. For more information about bats
and rabies or histoplasmosis, including what to do if a
person makes contact with a bat, contact the
Centers for Disease Control
and Prevention (CDC).
Bat Conservation
Bats, like many other wildlife species,
have lost a great deal of natural habitat to development.
Some species have been able to adapt to habitat loss by
moving into man-made structures. Female bats of some species
will roost in large colonies when they have their pups.
The potential of exterminating large numbers of bats at
once means that bat populations are particularly vulnerable
to extirpation.
Unwelcome Guests
When bats take up residence in a structure
where they are not wanted, there is only one safe, legal,
and effective technique for getting rid of them. The process
is known as "exclusion”. Excluding bats from their roost
sites involves the use of a one-way device which allows
them to exit the structure, but prevents them from returning.
Exclusion devices should be used for four consecutive days
before the opening is sealed. However, when outdoor temperatures
begin to drop, so does insect activity. Therefore, when
colder weather comes to Florida, there is little food available
and bats may become inactive. Some bats might not exit the
structure in which they roost during cold weather. In order
to keep bats from being trapped inside of a structure, bat
exclusion devices may not be used if the National Weather
Service forecasts four consecutive days of the minimum temperature
below 50 degrees Fahrenheit. Following exclusion, the structure
needs to be rendered inaccessible to prevent recolonization
by sealing all entrance points. These small mammals can
enter a building through the tiniest of openings. Bat-proofing
can be as easy as performing a few simple, energy-efficient
home improvements such as applying caulking, and weather
stripping.
The Benefits of Bats
Bats are a very important natural resource
for Florida because each bat can eat up to 3000 insects,
including mosquitoes and agriculture pests, per night. Bat
guano (feces) has been used for centuries as a nutrient
rich fertilizer and is still highly prized by gardeners.
Prohibitions
It is illegal to kill bats in Florida in
accordance with Florida Administrative Code number 68A-4.001
General Prohibitions and 68A-9.010 Taking Nuisance Wildlife.
The use of pesticides or poisons for the purpose of harming,
killing, or deterring bats is prohibited in the state of
Florida, with the exception of one registered repellent:
naphthalene (also known as moth balls). In order to avoid
illegal take of bats, a structure inhabited by bats should
not be sealed without first conducting an exclusion. Repellents
are not exclusionary devices and should only be used in
conjunction with an exclusion device if the structure is
going to be sealed. Due to the possibility of killing flightless
pups by separating them from their mothers, exclusion is
prohibited between April 16 and August 14. Exclusion is
also prohibited if the National Weather Service forecasts
four consecutive days of minimum temperatures below 50 degrees
Fahrenheit.
How You Can Help Protect Bats
- Avoid disturbing maternity colonies or entering
caves where bats are roosting.
- Never shoot, poison, or otherwise harm bats.
- Be cautious when using insecticides.
- Use caution when trimming trees and Spanish moss.
- Do not attempt to handle bats without the supervision
of a professional.
- Bats are very delicate creatures and are easily
injured if handled.
- Handling bats increases the chance that you
might be bitten.
- Construct a Bat House
- Bats are so effective at controlling insects
that some people attempt to attract bats with bat
houses. You can find information on constructing
or purchasing a bat house at the sites below.
- Become a friend of Bats!
- There are many bat organizations that need more
volunteers and support. Information on bat conservation
organizations are listed below
What is White Nose Syndrome in Bats?
White Nose Syndrome (WNS) is named for a
white fungus that has been found covering the muzzles of
hibernating bats in the northeastern part of the United
States. Thousands of bats with WNS have died. However, researchers
are uncertain whether the fungus is causing the bats to
die, or the fungus is secondary to some other primary cause
of death, such as a virus or environmental contaminant.
Bats known to be affected by WNS include the eastern pipistrelle,
northern long-eared bat, small-footed bat, little brown
bat, and the Indiana bat, which is protected by the Endangered
Species Act.
Why does this issue matter for Floridians?
No cases of WNS have been found in Florida, but WNS is apparently
spreading and biologists are still not certain whether bats
or people, or both bats and people are transmitting WNS
to new sites. Bats affected with WNS have been found in
caves in New York, Vermont, Massachusetts, and Connecticut.
In Florida, we have three species of bats that often roost
in caves and there is an active community of "cavers" -
people who regularly explore caves. Cavers that travel to
the northeastern United States and explore caves there should
disinfect their equipment as described in the information
at the link below. This will help ensure that WNS is not
transmitted to bats that roost in Florida caves.
Anyone in Florida who finds bats that appear
sick, or are acting in an unusual manner, should report
that information by calling FWC's Wildlife Alert phone number.
Bats affected by WNS do not always have the white fungus,
instead they may only appear emaciated or severely dehydrated.
Other signs of WNS include bats flying outside or near cave
openings during the day, and dead or dying bats on the ground.
Human health implications of WNS are not known, but there
is no indication that people have been affected by WNS or
exposure sick bats. Regardless, the public should never
handle sick, injured, or dead bats.
For additional information on WNS and methods
to appropriately disinfect caving equipment, go to this
link:
http://www.fws.gov/northeast/white_nose.html
More information:
Frequently Asked Questions
(FAQ)
Education
Bats for kids
page
Quick facts, classroom ideas, helpful links
Bats and Human Health
The Centers
For Disease Control and Prevention (CDC)
Bats and Rabies
Histoplasmosis
Bat Conservation Organizations
The
Florida Bat Conservancy
News, facts, bat houses, bats in buildings, and rehabilitation
Bat Conservation International
Professional and do-it-yourself exclusions, instructional
video, bat houses
Organization for
Bat Conservation
News, articles, gallery
Fly by night, "The Bat Specialists"
Bats in buildings, bat house orders, rescue, trivia, research
For additional technical assistance you
may contact the
FWC Regional
office nearest you.
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