Bats

Unknown

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