Paper on Bats

This essay has a total of 1716 words and 8 pages.

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
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