A Report On Bats- Essay, Research Paper
A Report on Bats-
INTRODUCTION
There is an abundant amount of animal species in the
world. They all have adapted and evolved to survive in
their surroundings. Some have grown fins, others legs, and
still others wings. One of the animals that has grown wings
is the bat. The bat is a truly great creature. It has all
the characteristics of mammals while also possessing the
skill of a bird in flight.
There are more than 800 species of bats in the
world. They are of many different sizes, shapes, and
lifestyles. They live all over the world and have drawn the
curiosity of millions. Bats also have the unique feature of
echolocation that it uses to catch insects. Though other
mammals, like the flying squirrel seem to fly but actually
glide, the bat is the only mammal that can truly fly (Lauber
1968).
A BAT’S BODY
Due to the great variety of species of bats some
characteristics vary greatly, but the Little Brown Bat is a
good example of a common bat. It has fur on the body, large
naked ears, the rear legs have claws, a tail membrane, and
it has the most distinguishing feature of a bat, wings
(Lauber 1968). The upper arm of the bat is short while the
forearm is very long (Fig. 1). The wrist is very small and
from it comes the thumb and the four longer fingers. The
thumb is short and used for climbing or walking. The
fingers are long and thin. Interlocking the fingers is the
wing. This arrangement of having the fingers in the wing
gives the bat amazing flight maneuverability (Honders 1975).
These bones look similar to a human hand. They are
connected by rubbery skin to the bat’s body enveloping all
the fingers but the thumb (Anonymous 1990).
Echolocation
Bats have a sixth sense called echolocation. This
was first proved by Donald Griffin. Bats produce ultrasonic
sound waves and then use the echo of the returning sound to
sense the world around them and in particularly to catch
insects. These sounds are usually out of the humans range
of hearing (Fellman 1993). This system is similar to that
of dolphins. The sound is in the form of clicks that
increase as the bat gets closer to the insect or whatever it
is tracking (Anonymous 1990).
Unlike humans, most insects can hear the bat’s
echolocation sounds. David D. Yager of the University of
Maryland has found that the praying mantis has used this to
its advantage. When being pursued by a bat the mantis can
hear the clicks of the bat behind it and to avoid being
eaten goes into a series of evasive maneuvers. First they
extend their fore limbs, then they extend their abdomens
which stop them. Then they go into a dive achieving a pace
twice their usual speed and if still being pursued will
crash into the ground to avoid being eaten. This and other
insects also use hearing to their advantage (Amato 1991).
Moths also do amazing maneuvers in attempts of escape,
similar to the mantis. Tiger moths even make their own
ultrasonic clicks. It is not known whether these are to
startle the bat or to warn it that the moth is distasteful
(Fellman 1993).
Despite the insects great efforts to foil the bat s
sonar the bat still catches its prey more than fifty percent
of the time (Fellman 1993). Some bats even have different
frequencies than insects can hear. The competition between
insects and bats will go on forever because they will
counter each other’s counter measures by evolving new
strategies, and as James Fullard said Evolution never
stops.
HIBERNATION AND MIGRATION
The food of bat usually becomes scarce during winter
months so some bats hibernate while others migrate (Honders
1975 and Bourliere 1995). When bats migrate they usually
move from the South to far North during the summer and they
return during the fall. Bats that hibernate prepare for the
winter by getting fat in autumn. Then they fall into a
sleep more extreme than their normal daily sleep. As in
most animals, when hibernating their major bodily functions,
such as heart-rate and breathing, are suppressed greatly.
Bats are known to interrupt their hibernation because they
have been seen in the winter.
Disturbing bats during hibernation can be very
destructive (Pistorius 1994). This is because the bats have
a limited supply of energy. The energy used when the bat is
awake is huge compared to that when it is hibernating. Bats
arise on occasion anyway to groom, or sometimes take a
flight outside, and even to move to colder places, where
they can survive with lower metabolism and save energy.
Repeated awakenings can result in starvation during the late
winter from lack of energy stores. In an extreme case in
Kentucky, during the 1960 s where a cave was a tourist
attraction, the population of 100,000 bats starved to death
after being awakened on several occasions.
REPRODUCTION
Bats have internal fertilization and give birth to
highly matured young like humans (Lauber 1968, Honders 1975,
and Ezzel 1992). Most bats only have one baby a year. The
bats mate in the roost and have little or no courtship. The
pregnant mothers form separate nursing colonies from the
others. Some species like the Mexican free-tailed bat, who
migrate immediately after mating, produce a secretion that
preserves the male s sperm until they reach their new roost.
When their baby is being born the mother hangs by
her thumbs to a tree branch. Its tail membrane acts as a
cradle and the baby is born into it tail first. Then the
mother hangs by one wing and cleans the baby with the other.
It is then attached to the mother s teat where it will hold
on during flight. In some species the baby is left at the
roost when the mother is hunting, in others the baby is
taken along. In the species that carry their young
eventually the baby grows too big for the mother and is left
in the roost. The bat then learns to fly and hunt its prey
by itself (Lauber 1968).
SPECIALIZED BATS
Some bats have developed special ways of adapting to
their surroundings. Though most bats eat insects, some feed
on fruit, nectar, small vertebrates, fish, and blood
(Bourliere 1995). The bats that eat fruit help disperse
seeds by eating and then dropping the seeds in their
droppings during flight. Those that drink nectar act like
hummingbirds pollinating flowers (Anonymous 1991). Bats
that eat small vertebrates along with insects and fruit are
often called false vampires. These bats eat lizards, tree
frogs, birds, rodents, and smaller bats. They kill their
prey by using their strong jaws and teeth to break their
neck. These bats have only about a two foot wingspan so
their prey tends to be small. Bats that catch fish fly just
above the water and catch the fish with its hind feet and
use its sharp claws to hold it. It then maneuvers the fish
to kill it by biting it (Novick 1973).
The most famous of bats is probably the vampire.
The vampire bat drinks the blood of large vertebrates when
they are asleep. To help in doing this they have developed
large incisors, a specialized tongue, and specialized saliva
to prevent blood from clotting. They are also able to move
quickly on the ground in case of their prey waking up and it
is too full of blood to fly away (Honders 1975).
MYTHS
There are many misconceptions about bats (Anonymous
1990). People think they are all dangerous because they
carry rabies. Less than one percent of all bats is infected
with rabies. Some people think they become caught in
people s hair, but this is also untrue. Other people think
lots of bats drink blood but this is also untrue, only three
species of bats drink blood. These prefer cattle blood and
only live in Latin America.
Bats are actual quite helpful to humans (Van Dyke
1994). Bats are important to many plants in the United
States because they help pollinate flowers. Most bats eat
insects, this is extremely helpful to humans. They help
keep bug populations low. Some bats, such as the little
brown bat, can consume about 600 mosquitoes in an hour.
Bats also keep the population down of other potential pests
such as leafhoppers, cucumber beetles, and June bugs.
Despite bats being helpful they can still be
dangerous under certain conditions (Anonymous 1988). Bat
droppings, or guano, are known to have spores and fungus in
them that cause Histoplasmosis, a lung infection, and other
diseases. Rabid bats can also be a threat because if one
attacks the victim can easily be infected with rabies. If
anyone ever has to handle a bat always wear gloves to
prevent bites.
Bats are a good example of how an animal can evolve
to have amazing abilities. Bats have evolved to fly, use
echolocation, hibernate, sleep in the day, hang by their
feet, and many other things that individual species have
developed. Some large bats, called megabats, are even
thought by some scientists to be closely related to primates
because of their similar brain tissue. Bats are highly
evolved animals that have amazing characteristics (Gibbons
1992 and Bailey et al. 1992).
LITERATURE CITED
Anonymous. 1988. Bats. Pamphlet distributed by Missouri Department
of Health. pp 1-2.
Anonymous. 1990. Bats In Connecticut. Pamphlet from Connecticut
Department of Environmental Protection. pp 1-8.
Anonymous. 1991. Warning From Bat Conservation International.
Pamphlet from Animal Welfare Institution. pp 1.
Amato, I. 1991. Praying Mantises Play Top Gun . Science 252: 781
Bailey, W. et al. 1992. Rejection Of The Flying Primate
Hypothesis . Science 256: 86-89
Bourliere, F. 1995. Mammals of The World. Alfred A. Knopf, New
York. pp 190-196
Ezzel, C. 1992. Cave Creatures . Science News 141: 88-90
Fellman, B. 1993. Guess Who s Coming to Dinner . National Wildlife
31: 42-45
Gibbons, A. 1992. Is Flying Primate Hypothesis Headed for a Crash
Landing? . Science 256: 34
Honders, J. 1975. The World of Mammals. Peebles Press, New York.
pp 22-23.
Lauber, P. 1968. Bats Wings in the Night. Random House, New York.
pp 1-15
Novick, A. 1973. Bats Aren t All Bad . National Geographic 143:
615- 627.
Pistoris, A. 1994. Forever Protected . Harrowsmith Country Life
28-35.
Van Dyke, L. 1994. Batting Down Bugs . Sierra Magazine 36-68