Bats
INTRODUCTION
There are an innumerous 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 in flight of a bird.
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 quality 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 1).
A Bats 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 bat. It has fur on its
body, large naked ears, its rear legs have claws, it has a tail membrane, and
it has the most distinguishing feature of a bat, wings (Lauber 9). The upper
arm of the bat is short while the forearm is very long. 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 set up of having the fingers in the
wing gives the bat amazing flight maneuverability (Honders 22). 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 (Bats in CT 1).
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
42).
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 (Bats in CT).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 and then extend their
abdomens that stops them. Then they go into a dive going 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 781).
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.Despite the insects great efforts to foil the bats sonar the bat still
catches its prey more than 50% of the time (Fellman 93). 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 others counter
measures of how an animal can evolve to how 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, Bailey et al. 1992)
HIBERNATION AND MIGRATION
The food of bat usually becomes scarce during winter months so some bats
hibernate while others migrate (Honders 75, Bourliere 95).
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
94). 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 in the late winter
from lack of energy stores. In an extreme case in Kentucky, during the 1960s
where a cave was a tourist attraction ,the population of 100,000 bats starved to
death after being awakened so many times.
REPRODUCTION
Bats have internal fertilization and give birth to highly matured young
like humans (Lauber, Honders 75, Ezzel 92). 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 males 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 mothers 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 to big for the mother and is left in the roost. The bat then learns to
fly and hunt its prey by itself (Lauber).
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 95). The bats that eat fruit help disperse seeds by eating
fruit and then dropping the seeds in their droppings during flight. Those that
drink nectar act like hummingbirds pollinating flowers (Warning from Bat
Conservation International 91). 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 thier
strong jaws and teeth to break their neck.
These bats have only about a two
foot wingspan so thier 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 73).The most famous of bats is probably the vampire. The vampire bat drinks
the blood of large vertebrates, to do this they have developed large incisors,
a specialized tongue, and specialized saliva to prevent blood from clotting, and
they are able to move quickly on the ground in the case of its prey waking up
and it is too full to fly away (Honders 75).
Science
